Biventricular Versus Right Ventricular Pacing in Heart Failure Patients With Atrioventricular Block (BLOCK HF)

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00267098

Acronym

BLOCK HF

Enrollment

918

Registered

2005-12-20

Start date

2003-12-31

Completion date

2013-03-31

Last updated

2014-03-26

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Atrioventricular Block, Heart Diseases

Keywords

Atrioventricular block, Cardiac Resynchronization Therapy, Pacemaker, Defibrillator, NYHA Class I, II or III Heart failure

Brief summary

Heart failure is a progressive disease that decreases the pumping action of the heart. This may cause a backup of fluid in the heart and may result in heart beat changes. When there are changes in the heartbeat, sometimes a pacemaker is used to control the rate and rhythm of the heartbeat. In this trial, the researchers will test if pacing both the left and right lower half of the heart (ventricles) will: * decrease the number of hospital and clinic visits due to heart failure symptoms * extend life * delay heart failure symptoms as compared to those who are paced in only one ventricle (the right ventricle)

Interventions

DEVICECardiac Resynchronization Therapy (CRT)

Biventricular pacing

Study design

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

Masking

DOUBLE (Subject, Outcomes Assessor)

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Inclusion criteria

* Subject has standard class I or class IIa indication for pacemaker implantation in accordance with ACC/AHA/HRS guidelines * Subjects diagnosed with atrioventricular (AV) block. An AV block is a disturbance when the heart's natural pacemaker sends a message from the atrium (top part of heart) to the ventricle (bottom part of heart) and the message is partially or totally blocked * Subject is receiving first time implant * Subjects with heart failure but no symptoms of it (New York Heart Association \[NYHA\] Class I), or subjects with mild heart failure that only sometimes interferes with their daily activities (NYHA Class II), or subjects with heart failure that severely limits daily activities (NYHA Class III) * Subjects with documented reduced heart pumping function (left ventricular ejection fraction ≤ 50%) within past 90 days * Subject is at least 18 years old * Subject or authorized legal guardian or representative has signed and dated the Informed Consent * Subject is able to receive a pectoral implant * Subject is expected to remain available for follow-up visits at the study center * Subject is willing and able to comply with the protocol

Exclusion criteria

* Subject has ever had a previous or has an existing device implant * Subjects with some forms of chest pain or myocardial infarction (heart attack) within the past 30 days * Subjects with coronary bypass within the past 30 days * Subjects with stent within the past 30 days * Subjects with valve repair or replacement within the past 6 months or is indicated for repair or replacement * Subjects with a mechanical right heart valve * Subject is indicated for a biventricular pacing device (CRT-P or CRT-D devices) * Subject is enrolled in a concurrent study which may confound the results of this study (co-enrollment in any concurrent clinical study requires approval of the study manager) * Subject is pregnant, or of child bearing potential and not on a reliable form of birth control * Subjects with a previous heart transplant * Subjects has been classified as NHYA Functional Class IV within prior 90 days (subjects with severe heart failure and should always be resting) * Subject, legal guardian or authorized representative is unable or unwilling to cooperate or give written informed consent

Design outcomes

Primary

Measure	Time frame	Description
Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	Events include all-cause mortality, heart failure(HF)-related urgent care (a healthcare utilization visit involving intravenous(IV) therapy for heart failure) or significant increase(at least 15%) in LVESVI (a measure of the volume of a patient's left ventricle) from randomization to a later time point. Time from randomization until the subject experienced one of these events served as the outcome measure. LVESVI endpoints occurred primarily at those visits in which LVESVI measurements were required (6, 12, 18, 24 months). Because endpoints such as death or HF urgent care could occur at any time during follow-up, the subject's outcome measure could range from less than 1 month to 105 months (maximum follow-up duration). Primary endpoints and follow-up data occurring after a subject missed a required LVESVI measurement were excluded from the analysis and the table below. The counts reflect the number of subjects meeting each endpoint, and are not necessarily mutually exclusive.

Secondary

Measure	Time frame	Description
All-Cause Mortality	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	The endpoint is the time to death from any cause. The rate of mortality, as measure by the hazard rate, in each randomization arm will be compared. This outcome includes all post-randomization deaths, whereas the reporting of the primary outcome excluded primary endpoints (including deaths) that occurred after the subject had missed a study-required echocardiogram (used to determine if the LVESVI primary endpoint was met).
All-Cause Mortality or Heart Failure-related Hospitalization	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	The endpoint will be a subject's time from randomization to either their first heart failure-related hospitalization, or death.
All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	The endpoint will be the time from randomization to either death or a visit (6, 12, 18, 24 month or interim visit) in which the subject undergoes an echocardiogram and the measured left ventricular end systolic volume index (a measure of the size of the subject's left ventricle normalized over their body surface area) is at least 15% greater than the corresponding measured value at randomization. Only LVESVI endpoints/deaths and follow-up data occurring before a subject missed an LVESVI measurement (due to missed visit, echo not performed, etc.) were used in the analysis and included in the table below. The counts reflect the number of subjects meeting each endpoint, and are not mutually exclusive.
First Heart Failure Hospitalization	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	The endpoint is the time from randomization to a subject's first heart failure (HF)-related hospitalization. For each randomization arm, the number of subjects who met the endpoint, experiencing at least one heart failure-related hospitalization post-randomization, are reported, as well as the number of randomized subjects who did not experience any HF hospitalizations post-randomization.
Days Hospitalized for Heart Failure	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	For each subject the endpoint was the days hospitalized for heart failure per patient year, calculated as the total number of days the subject was hospitalized for heart failure divided by the subject's total follow-up time. Only post-randomization data were used.
Change in New York Heart Association Classification	Randomization to 24 Months	The endpoint is a subject's change in New York Heart Association Classification (a measure of the degree of heart failure a subject has on a 4 class scale, with NYHA I being the healthiest score and NYHA IV being the sickest score) from randomization to each of four time points: 6 months, 12 months, 18 months, and 24 months post-randomization. The change categories listed will be relative to randomization.
Change in Heart Failure Stage	Randomization to 24 Months	The endpoint is a subject's change in Heart Failure Stage (a measure of the degree of heart failure a subject has on a 4 stage scale (A, B, C, D), with Class A being the healthiest score and Class D being the sickest score) from randomization to each of four time points: 6 months, 12 months, 18 months, and 24 months.
Change in Cardiovascular Medications	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	The endpoints are what classes of drugs (e.g. Beta blockers, Diuretics, Nitrates, etc.) each subject was on at the time of scheduled visits (e.g Randomization, 6 months, 12 months, etc.)
Frequency of Adverse Events Post-randomization	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	Adverse events that subjects experienced after they were randomized were compared between arms with regard to several categories such as heart failure (HF)-relatedness, relatedness to the implant procedure, and relatedness to the implanted system, including individual components such as the left ventricular (LV) lead and the CRT-P or CRT-D generator.
Cardiovascular-related Healthcare Utilizations	Participants were followed for the duration of the study, an average of 39.8 months post-randomization.	Cardiovascular-related healthcare utilizations (HCUs), such as hospitalizations, Emergency Department visits, urgent care visits, and clinic visits that subjects experienced after being randomized were summarized for each randomization arm
Change in Quality of Life at 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in Quality of Life score from randomization to 6 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 6 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.
Change in Quality of Life at 12 Months	Randomization to 12 months	The endpoint will be a subject's change in Quality of Life score from randomization to 12 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 12 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.
Change in Quality of Life at 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in Quality of Life score from randomization to 18 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 18 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.
Change in Quality of Life at 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in Quality of Life score from randomization to 24 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 24 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.
Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 6 month - randomization visit difference in LVEF value.
Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 12 month - randomization visit difference in LVEF value.
Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 18 month - randomization visit difference in LVEF value.
Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 6 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.
Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 24 month - randomization visit difference in LVEF value.
Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 6 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.
Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 12 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.
Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 18 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.
Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 24 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.
Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 12 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.
Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 18 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.
Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 24 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.
Change in Left Ventricular Mass (LV Mass) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 6 months. For each subject the measurement was calculated as 6 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.
Change in Left Ventricular Mass (LV Mass) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 12 months. For each subject the measurement was calculated as 12 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.
Change in Left Ventricular Mass (LV Mass) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 18 months. For each subject the measurement was calculated as 18 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.
Change in Left Ventricular Mass (LV Mass) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 24 months. For each subject the measurement was calculated as 24 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.
Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 6 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.
Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 12 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.
Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 18 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.
Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 24 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.
Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 6 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.
Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 12 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.
Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 18 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.
Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 24 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.
Change in Mitral Regurgitation From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 6 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.
Change in Mitral Regurgitation From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 12 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.
Change in Mitral Regurgitation From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 18 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.
Change in Mitral Regurgitation From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 24 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.
Change in Cardiac Index From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 6 months. The measure for each subject will be the 6 month - randomization visit value.
Change in Cardiac Index From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 12 months. The measure for each subject will be the 12 month - randomization visit value.
Change in Cardiac Index From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 18 months. The measure for each subject will be the 18 month - randomization visit value.
Change in Cardiac Index From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 24 months. The measure for each subject will be the 24 month - randomization visit value.
Change in Interventricular Mechanical Delay (IVMD) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 6 month visit. The measure will be the 6 month - randomization visit difference in IVMD.
Change in Interventricular Mechanical Delay (IVMD) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 12 month visit. The measure will be the 12 month - randomization visit difference in IVMD.
Change in Interventricular Mechanical Delay (IVMD) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 18 month visit. The measure will be the 18 month - randomization visit difference in IVMD.
Change in Interventricular Mechanical Delay (IVMD) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 24 month visit. The measure will be the 24 month - randomization visit difference in IVMD.
Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 6 Months	Randomization to 6 Months	The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 6 months. The measure for each subject will be the 6 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.
Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 12 Months	Randomization to 12 Months	The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 12 months. The measure for each subject will be the 12 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.
Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 18 Months	Randomization to 18 Months	The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 18 months. The measure for each subject will be the 18 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.
Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 24 Months	Randomization to 24 Months	The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 24 months. The measure for each subject will be the 24 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.
Clinical Composite Score at 6 Months	Randomization to 6 Months	The endpoint will be a subject's Clinical Composite Score at 6 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.
Clinical Composite Score at 12 Months	Randomization to 12 Months	The endpoint will be a subject's Clinical Composite Score at 12 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.
Clinical Composite Score at 18 Months	Randomization to 18 Months	The endpoint will be a subject's Clinical Composite Score at 18 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.
Clinical Composite Score at 24 Months	Randomization to 24 Months	The endpoint will be a subject's Clinical Composite Score at 24 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.
CRT-P and CRT-D System Implant Success	Initial Implant Procedure	The endpoint will be whether each subject who underwent an implant attempt of a Cardiac Resynchronization Therapy device, be it a pacing only device (CRT-P) or a pacing device with defibrillation capability (CRT-D), had a successful procedure (i.e. the generator, left ventricular lead, and right ventricular lead were successfully implanted). Only one implant attempt was allowed.
Incidence of Ventricular Tachyarrhythmias	Participants were followed for the duration of the study, an average of 37.9 months post-randomization among CRT-D subjects.	Among subjects implanted with a Cardiac Resynchronization Therapy with Defibrillation device (CRT-D) and randomized, the endpoint was the time from randomization until the subject experienced a ventricular tachyarrhythmia. For each randomization arm, the number of CRT-D subjects who experienced at least one ventricular tachyarrhythmia post-randomization is reported, as well as the number of CRT-D subjects who did not experience one or more ventricular tachyarrhythmias post-randomization.

Countries

Canada, United States

Participant flow

Participants by arm

Arm	Count
No Implant Attempt Subjects who did not undergo an implant attempt of a CRT-P or CRT-D device and were not randomized	109
Unsuccessful Implants Subjects who underwent an implant attempt of a CRT-P or CRT-D device but were not successfully implanted	51
CRT-P: Biventricular Pacing Arm Subjects who were implanted with a CRT-P device and randomized to receive biventricular pacing	243
CRT-P: Right Ventricular Pacing Arm Subjects who were implanted with a CRT-P device and randomized to receive right ventricular pacing	241
CRT-P: Not Randomized Subjects successfully implanted with a CRT-P device who were not randomized	47
CRT-D: Biventricular Pacing Arm Subjects implanted with a CRT-D device and randomized to receive biventricular pacing	106
CRT-D: Right Ventricular Pacing Arm Subjects implanted with a CRT-D device and randomized to receive right ventricular pacing.	101
CRT-D: Not Randomized Subjects successfully implanted with a CRT-D device who were not randomized	20
Total	918

Withdrawals & dropouts

Period	Reason	FG000	FG001	FG002	FG003	FG004	FG005	FG006	FG007
Overall Study	Death	0	0	57	66	14	23	28	9
Overall Study	Explanted Medtronic device	0	0	0	1	0	0	0	0
Overall Study	Inclusion/Exclusion Criteria Not Met	96	0	0	0	2	0	0	0
Overall Study	Lost to Follow-up	0	0	6	5	2	3	1	1
Overall Study	Non-Medtronic LV Lead Implanted	0	0	0	0	2	0	0	0
Overall Study	Physician Decision	5	0	7	11	5	4	3	0
Overall Study	Site closure	0	0	0	1	0	1	1	0
Overall Study	Sponsor withdrew subject	0	0	0	1	0	0	0	0
Overall Study	Subject listed for heart transplant	0	0	0	0	0	0	1	0
Overall Study	Unsuccessful Implant Exit Per Protocol	0	51	0	0	0	0	0	0
Overall Study	Withdrawal by Subject	8	0	24	21	12	9	12	5

Baseline characteristics

Characteristic	No Implant Attempt	Unsuccessful Implants	CRT-P: Biventricular Pacing Arm	CRT-P: Right Ventricular Pacing Arm	CRT-P: Not Randomized	CRT-D: Biventricular Pacing Arm	CRT-D: Right Ventricular Pacing Arm	CRT-D: Not Randomized	Total
Age, Continuous	70.2 years STANDARD_DEVIATION 12.6	71.1 years STANDARD_DEVIATION 11.2	74.4 years STANDARD_DEVIATION 10.2	73.8 years STANDARD_DEVIATION 10.8	79.3 years STANDARD_DEVIATION 7.6	72.0 years STANDARD_DEVIATION 9.3	71.0 years STANDARD_DEVIATION 10	74.0 years STANDARD_DEVIATION 9.1	73.2 years STANDARD_DEVIATION 10.6
Race/Ethnicity, Customized African American	10 participants	3 participants	8 participants	10 participants	0 participants	4 participants	4 participants	1 participants	40 participants
Race/Ethnicity, Customized Asian	0 participants	0 participants	0 participants	0 participants	1 participants	0 participants	0 participants	0 participants	1 participants
Race/Ethnicity, Customized Caucasian	91 participants	45 participants	225 participants	224 participants	43 participants	96 participants	90 participants	18 participants	832 participants
Race/Ethnicity, Customized Hispanic	1 participants	0 participants	3 participants	1 participants	2 participants	2 participants	2 participants	1 participants	12 participants
Race/Ethnicity, Customized Native American	0 participants	0 participants	0 participants	1 participants	0 participants	0 participants	0 participants	0 participants	1 participants
Race/Ethnicity, Customized Other	1 participants	1 participants	1 participants	0 participants	0 participants	0 participants	2 participants	0 participants	5 participants
Race/Ethnicity, Customized Subject did not offer ethnicity	6 participants	2 participants	6 participants	5 participants	1 participants	4 participants	3 participants	0 participants	27 participants
Region of Enrollment Canada	0 participants	5 participants	11 participants	10 participants	0 participants	2 participants	3 participants	1 participants	32 participants
Region of Enrollment United States	109 participants	46 participants	232 participants	231 participants	47 participants	104 participants	98 participants	19 participants	886 participants
Sex: Female, Male Female	29 Participants	14 Participants	62 Participants	73 Participants	18 Participants	19 Participants	20 Participants	4 Participants	239 Participants
Sex: Female, Male Male	80 Participants	37 Participants	181 Participants	168 Participants	29 Participants	87 Participants	81 Participants	16 Participants	679 Participants

Adverse events

Event type	EG000 affected / at risk	EG001 affected / at risk	EG002 affected / at risk	EG003 affected / at risk	EG004 affected / at risk
deaths Total, all-cause mortality	— / —	— / —	— / —	— / —	— / —
other Total, other adverse events	193 / 349	181 / 342	16 / 67	8 / 51	0 / 109
serious Total, serious adverse events	223 / 349	219 / 342	41 / 67	6 / 51	2 / 109

Outcome results

Primary

Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)

Events include all-cause mortality, heart failure(HF)-related urgent care (a healthcare utilization visit involving intravenous(IV) therapy for heart failure) or significant increase(at least 15%) in LVESVI (a measure of the volume of a patient's left ventricle) from randomization to a later time point. Time from randomization until the subject experienced one of these events served as the outcome measure. LVESVI endpoints occurred primarily at those visits in which LVESVI measurements were required (6, 12, 18, 24 months). Because endpoints such as death or HF urgent care could occur at any time during follow-up, the subject's outcome measure could range from less than 1 month to 105 months (maximum follow-up duration). Primary endpoints and follow-up data occurring after a subject missed a required LVESVI measurement were excluded from the analysis and the table below. The counts reflect the number of subjects meeting each endpoint, and are not necessarily mutually exclusive.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Population: Only randomized subjects in both device groups were included in the analysis of this endpoint, as the analysis was restricted to post-randomization data. Subjects in the No Implant Attempt, Unsuccessful Implants, CRT-P: Not Randomized, and CRT-D: Not Randomized subgroups were excluded.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects Experiencing a Primary Endpoint	160 participants
Biventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects with an LVESVI Primary Endpoint	93 participants
Biventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects with an HF Urgent Care Primary Endpoint	70 participants
Biventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects who died	55 participants
Right Ventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects who died	66 participants
Right Ventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects Experiencing a Primary Endpoint	191 participants
Right Ventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects with an HF Urgent Care Primary Endpoint	94 participants
Right Ventricular Pacing Arm	Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)	Subjects with an LVESVI Primary Endpoint	136 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same rate of mortality, a heart failure urgent care visit, or significant increase in LVESVI as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a lower rate of this composite endpoint than patients with right ventricular pacing.p-value: 0.99995% CI: [0.592, 0.889]Posterior Distribution for HR

Secondary

All-Cause Mortality

The endpoint is the time to death from any cause. The rate of mortality, as measure by the hazard rate, in each randomization arm will be compared. This outcome includes all post-randomization deaths, whereas the reporting of the primary outcome excluded primary endpoints (including deaths) that occurred after the subject had missed a study-required echocardiogram (used to determine if the LVESVI primary endpoint was met).

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	All-Cause Mortality	Subjects who died	80 participants
Biventricular Pacing Arm	All-Cause Mortality	Subjects who did not die	269 participants
Right Ventricular Pacing Arm	All-Cause Mortality	Subjects who died	94 participants
Right Ventricular Pacing Arm	All-Cause Mortality	Subjects who did not die	248 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same rate of mortality as corresponding patients who receive right ventricular pacing.p-value: 0.86595% CI: [0.632, 1.142]Posterior Distribution for HR

Secondary

All-Cause Mortality or Heart Failure-related Hospitalization

The endpoint will be a subject's time from randomization to either their first heart failure-related hospitalization, or death.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who underwent HF hospitalization	79 participants
Biventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who died or underwent HF hospitalization	121 participants
Biventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who died	80 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who underwent HF hospitalization	92 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who died or underwent HF hospitalization	135 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Heart Failure-related Hospitalization	Subjects who died	94 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same rate of mortality or heart failure(HF)-related hospitalization as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a lower rate of death or first HF hospitalization than patients with right ventricular pacing.p-value: 0.978595% CI: [0.615, 0.991]Posterior Distribution for HR

Secondary

All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index

The endpoint will be the time from randomization to either death or a visit (6, 12, 18, 24 month or interim visit) in which the subject undergoes an echocardiogram and the measured left ventricular end systolic volume index (a measure of the size of the subject's left ventricle normalized over their body surface area) is at least 15% greater than the corresponding measured value at randomization. Only LVESVI endpoints/deaths and follow-up data occurring before a subject missed an LVESVI measurement (due to missed visit, echo not performed, etc.) were used in the analysis and included in the table below. The counts reflect the number of subjects meeting each endpoint, and are not mutually exclusive.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who died or experienced LVESVI event	131 participants
Biventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who died	55 participants
Biventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who experienced LVESVI event	93 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who died or experienced LVESVI event	171 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who died	66 participants
Right Ventricular Pacing Arm	All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index	Subjects who experienced LVESVI event	136 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or II who receive biventricular pacing have the same rate of mortality or significant increase in LVESVI as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a lower rate of death or significant increase in LVESVI than patients with right ventricular pacing.p-value: 0.988695% CI: [0.558, 0.866]Posterior Distribution for HR

Secondary

Cardiovascular-related Healthcare Utilizations

Cardiovascular-related healthcare utilizations (HCUs), such as hospitalizations, Emergency Department visits, urgent care visits, and clinic visits that subjects experienced after being randomized were summarized for each randomization arm

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization urgent care visit	12 participants
Biventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with a post-randomization CV HCU	264 participants
Biventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization hospitalization	164 participants
Biventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization ED visit	118 participants
Biventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization clinic visit	214 participants
Right Ventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization clinic visit	220 participants
Right Ventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization ED visit	128 participants
Right Ventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with a post-randomization CV HCU	263 participants
Right Ventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization urgent care visit	12 participants
Right Ventricular Pacing Arm	Cardiovascular-related Healthcare Utilizations	Subjects with post-randomization hospitalization	162 participants

Secondary

Change in Cardiac Index From Randomization to 12 Months

The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 12 months. The measure for each subject will be the 12 month - randomization visit value.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Cardiac Index From Randomization to 12 Months	-0.1 liters per minute per squared meter	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in Cardiac Index From Randomization to 12 Months	-0.2 liters per minute per squared meter	Standard Deviation 0.6

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Cardiac Index (CI) through 12 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Cardiac Index through 12 months with BiV pacing than RV pacing. Change was calculated as 12 month value - randomization visit value.95% CI: [-0.022, 0.198]Bayesian Credible Interval

Secondary

Change in Cardiac Index From Randomization to 18 Months

The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 18 months. The measure for each subject will be the 18 month - randomization visit value.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Cardiac Index From Randomization to 18 Months	-0.1 liters per minute per squared meter	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Cardiac Index From Randomization to 18 Months	0 liters per minute per squared meter	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Cardiac Index (CI) through 18 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Cardiac Index through 18 months with BiV pacing than RV pacing. Change was calculated as 18 month value - randomization visit value.95% CI: [-0.218, 0.058]Bayesian Credible Interval

Secondary

Change in Cardiac Index From Randomization to 24 Months

The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 24 months. The measure for each subject will be the 24 month - randomization visit value.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Cardiac Index From Randomization to 24 Months	-0.1 liters per minute per squared meter	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Cardiac Index From Randomization to 24 Months	-0.2 liters per minute per squared meter	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Cardiac Index (CI) through 24 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Cardiac Index through 24 months with BiV pacing than RV pacing. Change was calculated as 24 month value - randomization visit value.95% CI: [-0.095, 0.192]Bayesian Credible Interval

Secondary

Change in Cardiac Index From Randomization to 6 Months

The endpoint will be a subject's change in cardiac index (a measure of how much blood the left ventricle ejects in one minute, normalized over body surface area) from randomization to 6 months. The measure for each subject will be the 6 month - randomization visit value.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Cardiac Index From Randomization to 6 Months	0 liters per minute per squared meter	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in Cardiac Index From Randomization to 6 Months	-0.1 liters per minute per squared meter	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Cardiac Index (CI) through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Cardiac Index through 6 months with BiV pacing than RV pacing. Change was calculated as 6 month value - randomization visit value.95% CI: [-0.031, 0.195]Bayesian Credible Interval

Secondary

Change in Cardiovascular Medications

The endpoints are what classes of drugs (e.g. Beta blockers, Diuretics, Nitrates, etc.) each subject was on at the time of scheduled visits (e.g Randomization, 6 months, 12 months, etc.)

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Population: Because indications for defibrillation devices like CRT-Ds are defined by characteristics that relate to medication guidelines, medication results are presented separately for each device group. Medications were assessed only for subjects who completed visits (denoted as Subjects with Medications Assessed).

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on ACE-Inhibitors/ARBs	114 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects with Medications Assessed	152 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on ACE-Inhibitors/ARBs	147 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects with Medications Assessed	94 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Diuretics	111 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Aldosterone Antagonists	16 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Beta Blockers	158 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Aldosterone Antagonists	33 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Vasodilators/Nitrates	36 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Beta Blockers	134 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Vasodilators/Nitrates	45 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Aldosterone Antagonists	8 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on ACE-Inhibitors/ARBs	121 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects with Medications Assessed	169 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Aldosterone Antagonists	23 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Diuretics	69 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Aldosterone Antagonists	10 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Diuretics	156 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Beta Blockers	186 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Vasodilators/Nitrates	21 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Beta Blockers	86 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects with Medications Assessed	226 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on ACE-Inhibitors/ARBs	173 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on ACE-Inhibitors/ARBs	76 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects with Medications Assessed	109 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on ACE-Inhibitors/ARBs	162 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Vasodilators/Nitrates	15 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Diuretics	82 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Aldosterone Antagonists	14 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Beta Blockers	175 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Beta Blockers	75 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Vasodilators/Nitrates	23 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Beta Blockers	104 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Vasodilators/Nitrates	46 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Vasodilators/Nitrates	53 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on ACE-Inhibitors/ARBs	92 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects with Medications Assessed	130 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Aldosterone Antagonists	31 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Diuretics	57 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Diuretics	97 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Aldosterone Antagonists	18 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Diuretics	148 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on ACE-Inhibitors/ARBs	69 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Vasodilators/Nitrates	28 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Beta Blockers	118 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects with Medications Assessed	205 participants
Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Diuretics	133 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects with Medications Assessed	200 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on ACE-Inhibitors/ARBs	179 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Beta Blockers	191 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Vasodilators/Nitrates	44 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Aldosterone Antagonists	25 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Diuretics	158 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects with Medications Assessed	207 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on ACE-Inhibitors/ARBs	152 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Beta Blockers	171 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Vasodilators/Nitrates	42 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Aldosterone Antagonists	21 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Diuretics	137 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on ACE-Inhibitors/ARBs	151 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Beta Blockers	170 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Vasodilators/Nitrates	43 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Aldosterone Antagonists	20 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Diuretics	131 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects with Medications Assessed	181 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on ACE-Inhibitors/ARBs	137 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Beta Blockers	152 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Vasodilators/Nitrates	44 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Aldosterone Antagonists	21 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Diuretics	125 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects with Medications Assessed	157 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on ACE-Inhibitors/ARBs	119 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Beta Blockers	133 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Vasodilators/Nitrates	37 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Aldosterone Antagonists	15 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Diuretics	104 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects with Medications Assessed	131 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on ACE-Inhibitors/ARBs	102 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Beta Blockers	114 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Vasodilators/Nitrates	28 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Aldosterone Antagonists	14 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Diuretics	90 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects with Medications Assessed	112 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on ACE-Inhibitors/ARBs	85 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Beta Blockers	97 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Vasodilators/Nitrates	24 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Aldosterone Antagonists	19 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Diuretics	79 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects with Medications Assessed	99 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on ACE-Inhibitors/ARBs	73 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Beta Blockers	86 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Vasodilators/Nitrates	22 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Aldosterone Antagonists	13 participants
Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Diuretics	71 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Beta Blockers	98 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects with Medications Assessed	42 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects with Medications Assessed	53 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects with Medications Assessed	94 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Vasodilators/Nitrates	23 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on ACE-Inhibitors/ARBs	30 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Vasodilators/Nitrates	24 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Aldosterone Antagonists	9 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Vasodilators/Nitrates	12 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Beta Blockers	41 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on ACE-Inhibitors/ARBs	42 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Diuretics	74 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects with Medications Assessed	38 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Vasodilators/Nitrates	14 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Vasodilators/Nitrates	31 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Aldosterone Antagonists	13 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Aldosterone Antagonists	13 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Beta Blockers	51 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Beta Blockers	65 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Diuretics	57 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Beta Blockers	87 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on ACE-Inhibitors/ARBs	93 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Aldosterone Antagonists	8 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects with Medications Assessed	78 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Vasodilators/Nitrates	16 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Vasodilators/Nitrates	22 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Aldosterone Antagonists	20 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on ACE-Inhibitors/ARBs	62 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on ACE-Inhibitors/ARBs	58 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Beta Blockers	35 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Aldosterone Antagonists	19 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Beta Blockers	75 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Aldosterone Antagonists	10 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Beta Blockers	79 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Diuretics	31 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Vasodilators/Nitrates	22 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Diuretics	47 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on ACE-Inhibitors/ARBs	77 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Diuretics	34 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Aldosterone Antagonists	9 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Diuretics	66 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on ACE-Inhibitors/ARBs	72 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Diuretics	36 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Diuretics	51 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects with Medications Assessed	83 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on ACE-Inhibitors/ARBs	27 participants
CRT-D: Biventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects with Medications Assessed	69 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Vasodilators/Nitrates	20 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects with Medications Assessed	67 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on ACE-Inhibitors/ARBs	56 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Diuretics	70 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Beta Blockers	63 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects with Medications Assessed	42 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Vasodilators/Nitrates	10 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Aldosterone Antagonists	25 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Aldosterone Antagonists	18 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Aldosterone Antagonists	12 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	24 Months: Subjects on Diuretics	56 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Vasodilators/Nitrates	12 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects with Medications Assessed	57 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on ACE-Inhibitors/ARBs	35 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on ACE-Inhibitors/ARBs	47 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on Beta Blockers	79 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Beta Blockers	93 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Beta Blockers	56 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Vasodilators/Nitrates	11 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects on ACE-Inhibitors/ARBs	73 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Aldosterone Antagonists	15 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Beta Blockers	42 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	30 Months: Subjects on Diuretics	50 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	6 Months: Subjects with Medications Assessed	89 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects with Medications Assessed	44 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Diuretics	39 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on ACE-Inhibitors/ARBs	37 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Diuretics	74 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Beta Blockers	44 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	42 Months: Subjects on Vasodilators/Nitrates	10 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Vasodilators/Nitrates	9 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on Aldosterone Antagonists	25 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Aldosterone Antagonists	21 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	Randomization: Subjects on ACE-Inhibitors/ARBs	84 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Diuretics	60 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Vasodilators/Nitrates	13 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects with Medications Assessed	72 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Aldosterone Antagonists	10 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on ACE-Inhibitors/ARBs	58 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on Beta Blockers	75 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Beta Blockers	63 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Vasodilators/Nitrates	11 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects on ACE-Inhibitors/ARBs	70 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Aldosterone Antagonists	20 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	36 Months: Subjects on Diuretics	37 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	18 Months: Subjects on Diuretics	59 participants
CRT-D: Right Ventricular Pacing Arm	Change in Cardiovascular Medications	12 Months: Subjects with Medications Assessed	81 participants

Secondary

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 12 Months

The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 12 months. The measure for each subject will be the 12 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 12 Months	0.1 ratio	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 12 Months	0.2 ratio	Standard Deviation 1

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in E:A ratio (E/A) through 12 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in E:A ratio through 12 months with BiV pacing than RV pacing. Change was calculated as 12 month value - randomization visit value.95% CI: [-0.287, 0.058]Bayesian Credible Interval

Secondary

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 18 Months

The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 18 months. The measure for each subject will be the 18 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 18 Months	0.1 ratio	Standard Deviation 0.8
Right Ventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 18 Months	0.1 ratio	Standard Deviation 0.8

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in E:A ratio (E/A) through 18 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in E:A ratio through 18 months with BiV pacing than RV pacing. Change was calculated as 18 month value - randomization visit value.95% CI: [-0.136, 0.22]Bayesian Credible Interval

Secondary

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 24 Months

The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 24 months. The measure for each subject will be the 24 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 24 Months	0.2 ratio	Standard Deviation 0.8
Right Ventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 24 Months	0.1 ratio	Standard Deviation 0.9

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in E:A ratio (E/A) through 24 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in E:A ratio through 24 months with BiV pacing than RV pacing. Change was calculated as 24 month value - randomization visit value.95% CI: [-0.085, 0.311]Bayesian Credible Interval

Secondary

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 6 Months

The endpoint will be a subject's change in E:A ratio (a measure of diastolic function) from randomization to 6 months. The measure for each subject will be the 6 month - randomization visit difference in E:A ratio. Typical values for the E:A ratio at a single time point are 1.04 in men and 1.03 in women.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 6 Months	0 ratio	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 6 Months	0 ratio	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in E:A ratio (E/A) through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in E:A ratio through 6 months with BiV pacing than RV pacing. Change was calculated as 6 month value - randomization visit value.95% CI: [-0.18, 0.089]Bayesian Credible Interval

Secondary

Change in Heart Failure Stage

The endpoint is a subject's change in Heart Failure Stage (a measure of the degree of heart failure a subject has on a 4 stage scale (A, B, C, D), with Class A being the healthiest score and Class D being the sickest score) from randomization to each of four time points: 6 months, 12 months, 18 months, and 24 months.

Time frame: Randomization to 24 Months

Population: For each time point(e.g. 6 months), only subjects with HF Stage assessed at randomization and that time point were included in the analysis. Those who could not be analyzed at a time point(for reasons such as death, exit,missed visit,or HF Stage not assessed) are listed under the Comparative data not available category for that time point.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Improved by 2 stages since randomization	0 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Improved by 1 stage since randomization	11 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: No change from randomization	296 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Worsened by 1 stage since randomization	2 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Worsened by 2 stages since randomization	1 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Comparative data not available	38 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Improved by 2 stages since randomization	1 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Improved by 1 stage since randomization	7 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months: No change since randomization	258 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months: Worsened by 1 stage since randomization	15 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Worsened by 2 stages since randomization	1 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	12 Months: Comparative data not available	68 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Improved by 2 stages since randomization	0 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Improved by 1 stage since randomization	4 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months: No change since randomization	222 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Worsened by 1 stage since randomization	16 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Worsened by 2 stages since randomization	0 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	18 Months: Comparative data not available	107 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Improved by 2 stages since randomization	0 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months: Improved by 1 stage since randomization	4 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months: No change since randomization	196 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Worsened by 1 stage since randomization	16 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Worsened by 2 stages since randomization	1 participants
Biventricular Pacing Arm	Change in Heart Failure Stage	24 Months: Comparative data not available	132 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Worsened by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Improved by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Improved by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Improved by 1 stage since randomization	5 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Improved by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: No change from randomization	274 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Improved by 1 stage since randomization	5 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Worsened by 1 stage since randomization	14 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months:Worsened by 1 stage since randomization	19 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Worsened by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months: No change since randomization	225 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	6 Months: Comparative data not available	49 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months: Improved by 1 stage since randomization	6 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Improved by 2 stages since randomization	0 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Worsened by 1 stage since randomization	18 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Improved by 1 stage since randomization	8 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months: Comparative data not available	120 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months: No change since randomization	244 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months:Worsened by 2 stages since randomization	1 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months: Worsened by 1 stage since randomization	23 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	24 Months: No change since randomization	197 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months:Worsened by 2 stages since randomization	1 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	18 Months: Comparative data not available	93 participants
Right Ventricular Pacing Arm	Change in Heart Failure Stage	12 Months: Comparative data not available	66 participants

Comparison: Subjects' change in HF stage from randomization to 12 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.825Posterior Distribution for Average Rank

Comparison: Subjects' changes in HF stage from randomization to 6 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.534Posterior Distribution for Average Rank

Comparison: Subjects' changes in HF stage from randomization to 18 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.651Posterior Distribution for Average Rank

Comparison: Subjects' changes in HF stage from randomization to 24 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.425Posterior Distribution for Average Rank

Secondary

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 12 Months

The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 12 month visit. The measure will be the 12 month - randomization visit difference in IVMD.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 12 Months	38.5 ms	Standard Deviation 121.9
Right Ventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 12 Months	0.4 ms	Standard Deviation 128.9

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in IVMD through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in IVMD through 12 months with BiV pacing than RV pacing. Change was calculated as 12 month value - randomization visit value. A positive value reflected reduction in IVMD.95% CI: [2.841, 40.87]Bayesian Credible Interval

Secondary

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 18 Months

The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 18 month visit. The measure will be the 18 month - randomization visit difference in IVMD.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 18 Months	55.1 ms	Standard Deviation 135.7
Right Ventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 18 Months	-0.8 ms	Standard Deviation 136.7

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in IVMD through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in IVMD through 18 months with BiV pacing than RV pacing. Change was calculated as 18 month value - randomization visit value. A positive value reflected reduction in IVMD.95% CI: [6.247, 47.19]Bayesian Credible Interval

Secondary

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 24 Months

The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 24 month visit. The measure will be the 24 month - randomization visit difference in IVMD.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 24 Months	48.6 ms	Standard Deviation 138.1
Right Ventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 24 Months	-4.9 ms	Standard Deviation 133.3

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in IVMD through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in IVMD through 24 months with BiV pacing than RV pacing. Change was calculated as 24 month value - randomization visit value. A positive value reflected reduction in IVMD.95% CI: [1.999, 44.53]Bayesian Credible Interval

Secondary

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 6 Months

The endpoint will be a subject's change in interventricular mechanical delay (a measure of dyssynchrony between ventricles, measured in ms) from randomization to the 6 month visit. The measure will be the 6 month - randomization visit difference in IVMD.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 6 Months	49.9 ms	Standard Deviation 134.2
Right Ventricular Pacing Arm	Change in Interventricular Mechanical Delay (IVMD) From Randomization to 6 Months	-4.2 ms	Standard Deviation 136.1

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in IVMD through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in IVMD through 6 months with BiV pacing than RV pacing. Change was calculated as 6 month value - randomization visit value. A positive value reflected reduction in IVMD.95% CI: [10.04, 48.64]Bayesian Credible Interval

Secondary

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 12 Months

The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 12 month - randomization visit difference in LVEF value.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 12 Months	2.7 percentage	Standard Deviation 9.3
Right Ventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 12 Months	-0.5 percentage	Standard Deviation 9.4

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEF from randomization to 12 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEF from randomization to 12 months than patients with right ventricular pacing.95% CI: [1.618, 4.839]Bayesian Credible Interval

Secondary

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 18 Months

The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 18 month - randomization visit difference in LVEF value.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 18 Months	2.7 percentage	Standard Deviation 9.5
Right Ventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 18 Months	0.4 percentage	Standard Deviation 10.1

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEF from randomization to 18 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEF from randomization to 18 months than patients with right ventricular pacing.95% CI: [0.419, 4.066]Bayesian Credible Interval

Secondary

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 24 Months

The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 24 month - randomization visit difference in LVEF value.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 24 Months	2.0 percentage	Standard Deviation 9.6
Right Ventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 24 Months	-1.6 percentage	Standard Deviation 10.5

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEF from randomization to 24 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEF from randomization to 24 months than patients with right ventricular pacing.95% CI: [1.623, 5.604]Bayesian Credible Interval

Secondary

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 6 Months

The endpoint will be a subject's change in LV Ejection Fraction (a measure of the percentage of blood ejected from the left ventricle of the heart with each contraction). A normal range is 55% to 70%. For each subject the measure will be the 6 month - randomization visit difference in LVEF value.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 6 Months	3.0 percentage	Standard Deviation 8.4
Right Ventricular Pacing Arm	Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 6 Months	-0.3 percentage	Standard Deviation 8.9

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEF from randomization to 6 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEF from randomization to 6 months than patients with right ventricular pacing.95% CI: [1.886, 4.815]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 12 Months

The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 12 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 12 Months	-0.1 cm	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 12 Months	0.0 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDD from randomization to 12 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVEDD from randomization to 12 months than patients with RV pacing. Negative values reflect reductions in LVEDD.95% CI: [-0.287, -0.035]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 18 Months

The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 18 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 18 Months	-0.2 cm	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 18 Months	0.0 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDD from randomization to 18 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVEDD from randomization to 18 months than patients with RV pacing. Negative values reflect reductions in LVEDD.95% CI: [-0.293, -0.03]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 24 Months

The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 24 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 24 Months	-0.3 cm	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 24 Months	0.0 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDD from randomization to 24 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVEDD from randomization to 24 months than patients with RV pacing. Negative values reflect reductions in LVEDD.95% CI: [-0.39, -0.097]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 6 Months

The endpoint will be a subject's change in LVEDD (a measure of the dimension of the left ventricle at the end of diastole). For each subject the measure was the 6 month - randomization visit difference in LVEDD value. Negative values correspond to reductions in LVEDD.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 6 Months	-0.1 cm	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 6 Months	0.0 cm	Standard Deviation 0.6

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDD from randomization to 6 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVEDD from randomization to 6 months than patients with RV pacing. Negative values reflect reductions in LVEDD.95% CI: [-0.235, -0.014]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 12 Months

The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 12 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 12 Months	-7.0 ml/square meter of body surface area	Standard Deviation 20.6
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 12 Months	-1.1 ml/square meter of body surface area	Standard Deviation 22.2

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDVI from randomization to 12 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEDVI from randomization to 12 months than patients with right ventricular pacing.95% CI: [-9.467, -2.038]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 18 Months

The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 18 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 18 Months	-9.8 ml/square meter of body surface area	Standard Deviation 21.4
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 18 Months	-0.8 ml/square meter of body surface area	Standard Deviation 22.4

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDVI from randomization to 18 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEDVI from randomization to 18 months than patients with right ventricular pacing.95% CI: [-12.91, -4.681]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 24 Months

The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 24 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 24 Months	-6.9 ml/square meter of body surface area	Standard Deviation 24.9
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 24 Months	-0.1 ml/square meter of body surface area	Standard Deviation 23.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDVI from randomization to 24 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEDVI from randomization to 24 months than patients with right ventricular pacing.95% CI: [-11.37, -1.736]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 6 Months

The endpoint will be a subject's change in Left Ventricular End Diastolic Volume Index (a measure of the volume of blood in the left ventricle at the end of diastole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 6 month - randomization visit difference in LVEDVI. Negative values correspond to reductions in LVEDVI over time.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 6 Months	-6.2 ml/square meter of body surface area	Standard Deviation 19.2
Right Ventricular Pacing Arm	Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 6 Months	-0.3 ml/square meter of body surface area	Standard Deviation 19.5

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVEDVI from randomization to 6 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVEDVI from randomization to 6 months than patients with right ventricular pacing.95% CI: [-9.085, -2.562]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 12 Months

The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 12 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 12 Months	0.0 cm	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 12 Months	0.1 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESD from randomization to 12 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVESD from randomization to 12 months than patients with RV pacing. Negative values reflect reductions in LVESD.95% CI: [-0.236, 0.029]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 18 Months

The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 18 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 18 Months	-0.1 cm	Standard Deviation 0.7
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 18 Months	0.0 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESD from randomization to 18 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVESD from randomization to 18 months than patients with RV pacing. Negative values reflect reductions in LVESD.95% CI: [-0.204, 0.087]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 24 Months

The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 24 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 24 Months	-0.1 cm	Standard Deviation 0.8
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 24 Months	0.1 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESD from randomization to 24 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVESD from randomization to 24 months than patients with RV pacing. Negative values reflect reductions in LVESD.95% CI: [-0.339, -0.018]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 6 Months

The endpoint will be a subject's change in LVESD (a measure of the dimension of the left ventricle at the end of systole). For each subject the measure was the 6 month - randomization visit difference in LVESD value. Negative values correspond to reductions in LVESD.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 6 Months	-0.1 cm	Standard Deviation 0.6
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 6 Months	0.0 cm	Standard Deviation 0.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESD from randomization to 6 months as similar patients who receive right ventricular pacing. This was tested against the hypothesis that patients with BiV pacing have a different change in LVESD from randomization to 6 months than patients with RV pacing. Negative values reflect reductions in LVESD.95% CI: [-0.185, 0.055]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 12 Months

The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 12 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 12 Months	-6.8 ml/square meter of body surface area	Standard Deviation 18.7
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 12 Months	0.5 ml/square meter of body surface area	Standard Deviation 20.2

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESVI from randomization to 12 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVESVI from randomization to 12 months than patients with right ventricular pacing.95% CI: [-10.59, -3.829]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 18 Months

The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 18 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 18 Months	-8.8 ml/square meter of body surface area	Standard Deviation 18.9
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 18 Months	-0.5 ml/square meter of body surface area	Standard Deviation 19.9

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESVI from randomization to 18 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVESVI from randomization to 18 months than patients with right ventricular pacing.95% CI: [-11.86, -4.574]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 24 Months

The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 24 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 24 Months	-6.0 ml/square meter of body surface area	Standard Deviation 22.6
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 24 Months	1.4 ml/square meter of body surface area	Standard Deviation 21.3

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESVI from randomization to 24 months as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a different change in LVESVI from randomization to 24 months than patients with right ventricular pacing.95% CI: [-11.69, -2.846]Bayesian Credible Interval

Secondary

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 6 Months

The endpoint will be a subject's change in Left Ventricular End Systolic Volume Index (a measure of the volume of blood in the left ventricle at the end of systole, normalized over body surface area). In other words, a measure of the size of the left ventricle. For each subject the measure is the 6 month - randomization visit difference in LVESVI. Negative values correspond to reductions in LVESVI over time.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 6 Months	-6.8 ml/square meter of body surface area	Standard Deviation 17.1
Right Ventricular Pacing Arm	Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 6 Months	0.4 ml/square meter of body surface area	Standard Deviation 17.7

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in LVESVI from randomization to 6 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a different change in LVESVI from randomization to 6 months than patients with right ventricular pacing.95% CI: [-10.12, -4.214]Bayesian Credible Interval

Secondary

Change in Left Ventricular Mass (LV Mass) From Randomization to 12 Months

The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 12 months. For each subject the measurement was calculated as 12 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 12 Months	-15.8 grams	Standard Deviation 46.8
Right Ventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 12 Months	-4.7 grams	Standard Deviation 52.4

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in LV Mass through 12 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in LV Mass through 12 months with BiV pacing than RV pacing. Change was calculated as 12 month value - randomization visit value.95% CI: [-19.33, -0.857]Bayesian Credible Interval

Secondary

Change in Left Ventricular Mass (LV Mass) From Randomization to 18 Months

The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 18 months. For each subject the measurement was calculated as 18 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 18 Months	-16.8 grams	Standard Deviation 48.8
Right Ventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 18 Months	-7.2 grams	Standard Deviation 49.8

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in LV Mass through 18 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in LV Mass through 18 months with BiV pacing than RV pacing. Change was calculated as 18 month value - randomization visit value.95% CI: [-18.19, 1.623]Bayesian Credible Interval

Secondary

Change in Left Ventricular Mass (LV Mass) From Randomization to 24 Months

The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 24 months. For each subject the measurement was calculated as 24 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 24 Months	-19.4 grams	Standard Deviation 45.1
Right Ventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 24 Months	-6.8 grams	Standard Deviation 49.6

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in LV Mass through 24 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in LV Mass through 24 months with BiV pacing than RV pacing. Change was calculated as 24 month value - randomization visit value.95% CI: [-21.11, -0.956]Bayesian Credible Interval

Secondary

Change in Left Ventricular Mass (LV Mass) From Randomization to 6 Months

The endpoint will be a subject's change in Left Ventricular Mass ( a measure of the size of the left ventricle) from randomization to 6 months. For each subject the measurement was calculated as 6 month - randomization visit difference in LV mass measurement. Negative values correspond to a reduction in LV mass over time.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 6 Months	-8.4 grams	Standard Deviation 43.1
Right Ventricular Pacing Arm	Change in Left Ventricular Mass (LV Mass) From Randomization to 6 Months	-4.2 grams	Standard Deviation 47.5

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in LV Mass through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in LV Mass through 6 months with BiV pacing than RV pacing. Change was calculated as 6 month value - randomization visit value.95% CI: [-12.13, 3.953]Bayesian Credible Interval

Secondary

Change in Mitral Regurgitation From Randomization to 12 Months

The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 12 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.

Time frame: Randomization to 12 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 12 Months	-1.3 percentage of left atrial area	Standard Deviation 12
Right Ventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 12 Months	-0.8 percentage of left atrial area	Standard Deviation 12.6

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Mitral Regurgitation (MR) through 12 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Mitral Regurgitation through 12 months with BiV pacing than RV pacing. Change was calculated as 12 month value - randomization visit value.95% CI: [-2.843, 1.773]Bayesian Credible Interval

Secondary

Change in Mitral Regurgitation From Randomization to 18 Months

The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 18 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 18 Months	-1.9 percentage of left atrial area	Standard Deviation 12.1
Right Ventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 18 Months	-1.9 percentage of left atrial area	Standard Deviation 11.5

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Mitral Regurgitation (MR) through 18 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Mitral Regurgitation through 18 months with BiV pacing than RV pacing. Change was calculated as 18 month value - randomization visit value.95% CI: [-2.379, 2.425]Bayesian Credible Interval

Secondary

Change in Mitral Regurgitation From Randomization to 24 Months

The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 24 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 24 Months	-1.1 percentage of left atrial area	Standard Deviation 13.6
Right Ventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 24 Months	-0.5 percentage of left atrial area	Standard Deviation 11.4

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Mitral Regurgitation (MR) through 24 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Mitral Regurgitation through 24 months with BiV pacing than RV pacing. Change was calculated as 24 month value - randomization visit value.95% CI: [-3.337, 2.046]Bayesian Credible Interval

Secondary

Change in Mitral Regurgitation From Randomization to 6 Months

The endpoint will be a subject's change in mitral regurgitation (a measure of how much blood flows backwards into the heart due to the mitral valve not closing properly). The measure for each subject will be the 6 month - randomization visit difference in mitral regurgitation. Negative values reflect reductions in mitral regurgitation over time.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 6 Months	-1.3 percentage of left atrial area	Standard Deviation 12.4
Right Ventricular Pacing Arm	Change in Mitral Regurgitation From Randomization to 6 Months	-0.6 percentage of left atrial area	Standard Deviation 11.2

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar changes in Mitral Regurgitation (MR) through 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients have different changes in Mitral Regurgitation through 6 months with BiV pacing than RV pacing. Change was calculated as 6 month value - randomization visit value.95% CI: [-2.828, 1.506]Bayesian Credible Interval

Secondary

Change in New York Heart Association Classification

The endpoint is a subject's change in New York Heart Association Classification (a measure of the degree of heart failure a subject has on a 4 class scale, with NYHA I being the healthiest score and NYHA IV being the sickest score) from randomization to each of four time points: 6 months, 12 months, 18 months, and 24 months post-randomization. The change categories listed will be relative to randomization.

Time frame: Randomization to 24 Months

Population: For each time point(e.g. 6 months), only subjects with NYHA assessed at both randomization and that time point were included in the analysis. Those who could not be analyzed at a time point(for reasons such as death, exit,missed visit,or NYHA not assessed at visit) are listed under the Comparative data not available category for that time point.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Improved by 2 classes from randomization	5 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months:Improved by 2 classes from randomization	3 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Improved by 2 classes from randomization	4 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Improved by 1 class from randomization	43 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: No change from randomization	200 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: No change from randomization	142 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Improved by 1 class from randomization	54 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Worsened by 1 class from randomization	50 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Worsened by 1 class from randomization	52 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months:Worsened by 2 classes from randomization	4 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: No change from randomization	172 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Comparative data not available	107 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Worsened by 2 classes from randomization	1 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Improved by 2 classes from randomization	2 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: Worsened by 1 class from randomization	49 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: Improved by 1 class from randomization	35 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Improved by 1 class from randomization	54 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: No change from randomization	135 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Worsened by 1 class from randomization	41 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Worsened by 2 classes from randomization	2 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Worsened by 2 classes from randomization	4 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Comparative data not available	37 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: Comparative data not available	132 participants
Biventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: Comparative data not available	68 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: No change from randomization	141 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Worsened by 1 class from randomization	41 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Improved by 2 classes from randomization	3 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Improved by 1 class from randomization	43 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: No change from randomization	205 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Worsened by 2 classes from randomization	1 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	6 Months: Comparative data not available	49 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Improved by 2 classes from randomization	5 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Improved by 1 class from randomization	34 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: No change from randomization	172 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: Worsened by 1 class from randomization	64 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months:Worsened by 2 classes from randomization	3 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	12 Months: Comparative data not available	64 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months:Improved by 2 classes from randomization	2 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Improved by 1 class from randomization	45 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: No change from randomization	126 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Worsened by 1 class from randomization	56 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months:Worsened by 2 classes from randomization	6 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	18 Months: Comparative data not available	92 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Improved by 2 classes from randomization	3 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: Improved by 1 class from randomization	36 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Worsened by 1 class from randomization	54 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months:Worsened by 2 classes from randomization	3 participants
Right Ventricular Pacing Arm	Change in New York Heart Association Classification	24 Months: Comparative data not available	120 participants

Comparison: Subjects' changes in NYHA classification from randomization to 6 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.591Posterior Distribution for Average Rank

Comparison: Subjects' changes in NYHA classification from randomization to 12 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.986Posterior Distribution for Average Rank

Comparison: Subjects' changes in NYHA classification from randomization to 18 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.726Posterior Distribution for Average Rank

Comparison: Subjects' changes in NYHA classification from randomization to 24 months were determined. The null hypothesis was that the average change among patients with biventricular pacing is equal to that of patients with right ventricular pacing.p-value: 0.701Posterior Distribution for Average Rank

Secondary

Change in Quality of Life at 12 Months

The endpoint will be a subject's change in Quality of Life score from randomization to 12 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 12 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.

Time frame: Randomization to 12 months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Quality of Life at 12 Months	3.9 units on a scale	Standard Deviation 20.1
Right Ventricular Pacing Arm	Change in Quality of Life at 12 Months	0.9 units on a scale	Standard Deviation 18.9

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in QOL score from randomization to 12 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a greater reduction (and thus improvement) in QOL score at 12 months than patients with right ventricular pacing.p-value: 0.9641Posterior Probability of Mean QOL Change

Secondary

Change in Quality of Life at 18 Months

The endpoint will be a subject's change in Quality of Life score from randomization to 18 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 18 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.

Time frame: Randomization to 18 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Quality of Life at 18 Months	2.3 units on a scale	Standard Deviation 20.5
Right Ventricular Pacing Arm	Change in Quality of Life at 18 Months	0.5 units on a scale	Standard Deviation 18.1

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in QOL score from randomization to 18 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a greater reduction (and thus improvement) in QOL score at 18 months than patients with right ventricular pacing.p-value: 0.8416Posterior Probability of Mean QOL Change

Secondary

Change in Quality of Life at 24 Months

The endpoint will be a subject's change in Quality of Life score from randomization to 24 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 24 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.

Time frame: Randomization to 24 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Quality of Life at 24 Months	2.6 units on a scale	Standard Deviation 20.5
Right Ventricular Pacing Arm	Change in Quality of Life at 24 Months	1.5 units on a scale	Standard Deviation 18.8

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in QOL score from randomization to 24 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a greater reduction (and thus improvement) in QOL score at 24 months than patients with right ventricular pacing.p-value: 0.727Posterior Probability of Mean QOL Change

Secondary

Change in Quality of Life at 6 Months

The endpoint will be a subject's change in Quality of Life score from randomization to 6 months. The Quality of Life score at a time point is calculated using the Minnesota Living with Heart Failure Questionnaire, which consists of 21 questions each on a 6 point scale from 0 to 5. The 21 scores are added up and the final score, ranging from 0 (best) to 105 (worst) is the subject's quality of life score. For each subject the measure will be the randomization visit - 6 month difference in QOL score, with positive values denoting a reduction in score and improvement in Quality of Life. Subjects with missing QOL scores at one or both time points were excluded from analysis, and so the number of subjects analyzed for this outcome was a subset of the number of randomized subjects.

Time frame: Randomization to 6 Months

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Change in Quality of Life at 6 Months	5 units on a scale	Standard Deviation 20.3
Right Ventricular Pacing Arm	Change in Quality of Life at 6 Months	0.3 units on a scale	Standard Deviation 19.4

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same average change in QOL score from randomization to 6 months as corresponding patients who receive right ventricular pacing.~This was tested against the hypothesis that patients with biventricular pacing have a greater reduction (and thus improvement) in QOL score at 6 months than patients with right ventricular pacing.p-value: 0.9976Posterior Probability of Mean QOL Change

Secondary

Clinical Composite Score at 12 Months

The endpoint will be a subject's Clinical Composite Score at 12 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.

Time frame: Randomization to 12 Months

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Clinical Composite Score at 12 Months	Improved	160 participants
Biventricular Pacing Arm	Clinical Composite Score at 12 Months	Unchanged	82 participants
Biventricular Pacing Arm	Clinical Composite Score at 12 Months	Worsened	103 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 12 Months	Improved	117 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 12 Months	Unchanged	78 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 12 Months	Worsened	146 participants

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar Clinical Composite Scores after 12 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients had better scores with BiV pacing than RV pacing. The analysis assigned numerical values (Improved=3, Unchanged=2, Worsened=1) and compared the average score between randomization arms using a one-sided analysis.p-value: 0.9999Posterior probability of mean difference

Secondary

Clinical Composite Score at 18 Months

The endpoint will be a subject's Clinical Composite Score at 18 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.

Time frame: Randomization to 18 Months

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Clinical Composite Score at 18 Months	Improved	137 participants
Biventricular Pacing Arm	Clinical Composite Score at 18 Months	Unchanged	68 participants
Biventricular Pacing Arm	Clinical Composite Score at 18 Months	Worsened	120 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 18 Months	Improved	103 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 18 Months	Unchanged	70 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 18 Months	Worsened	150 participants

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar Clinical Composite Scores after 18 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients had better scores with BiV pacing than RV pacing. The analysis assigned numerical values (Improved=3, Unchanged=2, Worsened=1) and compared the average score between randomization arms using a one-sided analysis.p-value: 0.9978Posterior probability of mean difference

Secondary

Clinical Composite Score at 24 Months

The endpoint will be a subject's Clinical Composite Score at 24 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.

Time frame: Randomization to 24 Months

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Clinical Composite Score at 24 Months	Improved	118 participants
Biventricular Pacing Arm	Clinical Composite Score at 24 Months	Unchanged	70 participants
Biventricular Pacing Arm	Clinical Composite Score at 24 Months	Worsened	120 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 24 Months	Improved	94 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 24 Months	Unchanged	59 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 24 Months	Worsened	161 participants

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar Clinical Composite Scores after 24 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients had better scores with BiV pacing than RV pacing. The analysis assigned numerical values (Improved=3, Unchanged=2, Worsened=1) and compared the average score between randomization arms using a one-sided analysis.p-value: 0.9983Posterior probability of mean difference

Secondary

Clinical Composite Score at 6 Months

The endpoint will be a subject's Clinical Composite Score at 6 months. The Clinical Composite Score is a 3 point score (Worsened, Unchanged, and Improved) based on a number of factors including: whether the subject has died, whether the subject has experienced a heart failure-related hospitalization, whether the subject has discontinued their therapy due to worsening heart failure, whether their New York Heart Association classification has improved or worsened since randomization, and whether they feel moderately or markedly better since randomization.

Time frame: Randomization to 6 Months

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Clinical Composite Score at 6 Months	Improved	184 participants
Biventricular Pacing Arm	Clinical Composite Score at 6 Months	Unchanged	83 participants
Biventricular Pacing Arm	Clinical Composite Score at 6 Months	Worsened	82 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 6 Months	Improved	133 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 6 Months	Unchanged	113 participants
Right Ventricular Pacing Arm	Clinical Composite Score at 6 Months	Worsened	96 participants

Comparison: The null hypothesis is that patients with AV block, NYHA I-III, and LVEF of at most 50% who receive RV pacing have similar Clinical Composite Scores after 6 months compared to similar patients who receive BiV pacing. This was tested against the alternative hypothesis that patients had better scores with BiV pacing than RV pacing. The analysis assigned numerical values (Improved=3, Unchanged=2, Worsened=1) and compared the average score between randomization arms using a one-sided analysis.p-value: 0.9985Posterior probability of mean difference

Secondary

CRT-P and CRT-D System Implant Success

The endpoint will be whether each subject who underwent an implant attempt of a Cardiac Resynchronization Therapy device, be it a pacing only device (CRT-P) or a pacing device with defibrillation capability (CRT-D), had a successful procedure (i.e. the generator, left ventricular lead, and right ventricular lead were successfully implanted). Only one implant attempt was allowed.

Time frame: Initial Implant Procedure

Population: For this outcome measure, only subjects in the No Implant Attempt subgroup were excluded.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	CRT-P and CRT-D System Implant Success	Subjects successfully implanted	531 participants
Biventricular Pacing Arm	CRT-P and CRT-D System Implant Success	Subjects not successfully implanted	30 participants
Right Ventricular Pacing Arm	CRT-P and CRT-D System Implant Success	Subjects successfully implanted	227 participants
Right Ventricular Pacing Arm	CRT-P and CRT-D System Implant Success	Subjects not successfully implanted	21 participants

Secondary

Days Hospitalized for Heart Failure

For each subject the endpoint was the days hospitalized for heart failure per patient year, calculated as the total number of days the subject was hospitalized for heart failure divided by the subject's total follow-up time. Only post-randomization data were used.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Value (MEAN)	Dispersion
Biventricular Pacing Arm	Days Hospitalized for Heart Failure	1.89 Days hospitalized per patient year	Standard Deviation 9.52
Right Ventricular Pacing Arm	Days Hospitalized for Heart Failure	2.63 Days hospitalized per patient year	Standard Deviation 16.08

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same rate of days hospitalized for heart failure per year as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a lower rate of days hospitalized for HF than patients with right ventricular pacing.p-value: 0.637Difference in Average Ranks

Secondary

First Heart Failure Hospitalization

The endpoint is the time from randomization to a subject's first heart failure (HF)-related hospitalization. For each randomization arm, the number of subjects who met the endpoint, experiencing at least one heart failure-related hospitalization post-randomization, are reported, as well as the number of randomized subjects who did not experience any HF hospitalizations post-randomization.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	First Heart Failure Hospitalization	Subjects experiencing a HF hospitalization	79 participants
Biventricular Pacing Arm	First Heart Failure Hospitalization	Subjects not experiencing a HF hospitalization	270 participants
Right Ventricular Pacing Arm	First Heart Failure Hospitalization	Subjects experiencing a HF hospitalization	92 participants
Right Ventricular Pacing Arm	First Heart Failure Hospitalization	Subjects not experiencing a HF hospitalization	250 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, and NYHA classifications of I, II, or III who receive biventricular pacing have the same rate of first heart failure(HF)-related hospitalization as corresponding patients who receive right ventricular pacing. This was tested against the hypothesis that patients with biventricular pacing have a lower rate of first HF hospitalization than patients with right ventricular pacing.p-value: 0.990495% CI: [0.522, 0.947]Posterior Distribution for HR

Secondary

Frequency of Adverse Events Post-randomization

Adverse events that subjects experienced after they were randomized were compared between arms with regard to several categories such as heart failure (HF)-relatedness, relatedness to the implant procedure, and relatedness to the implanted system, including individual components such as the left ventricular (LV) lead and the CRT-P or CRT-D generator.

Time frame: Participants were followed for the duration of the study, an average of 39.8 months post-randomization.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with CRT-P/CRT-D related AE(s)	12 participants
Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with system-related AE(s)	56 participants
Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with HF-related AE(s)	73 participants
Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with LV lead-related AE(s)	40 participants
Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with procedure-related AE(s)	37 participants
Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with LV lead-related AE(s)	12 participants
Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with CRT-P/CRT-D related AE(s)	17 participants
Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with HF-related AE(s)	106 participants
Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with system-related AE(s)	31 participants
Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with procedure-related AE(s)	7 participants
CRT-D: Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with LV lead-related AE(s)	14 participants
CRT-D: Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with procedure-related AE(s)	7 participants
CRT-D: Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with system-related AE(s)	47 participants
CRT-D: Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with CRT-P/CRT-D related AE(s)	36 participants
CRT-D: Biventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with HF-related AE(s)	45 participants
CRT-D: Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with CRT-P/CRT-D related AE(s)	18 participants
CRT-D: Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with system-related AE(s)	24 participants
CRT-D: Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with procedure-related AE(s)	2 participants
CRT-D: Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with LV lead-related AE(s)	4 participants
CRT-D: Right Ventricular Pacing Arm	Frequency of Adverse Events Post-randomization	Subjects with HF-related AE(s)	47 participants

Secondary

Incidence of Ventricular Tachyarrhythmias

Among subjects implanted with a Cardiac Resynchronization Therapy with Defibrillation device (CRT-D) and randomized, the endpoint was the time from randomization until the subject experienced a ventricular tachyarrhythmia. For each randomization arm, the number of CRT-D subjects who experienced at least one ventricular tachyarrhythmia post-randomization is reported, as well as the number of CRT-D subjects who did not experience one or more ventricular tachyarrhythmias post-randomization.

Time frame: Participants were followed for the duration of the study, an average of 37.9 months post-randomization among CRT-D subjects.

Population: Only randomized subjects in the CRT-D device group were included in the analysis of this endpoint, as the analysis was restricted to post-randomization data recorded by CRT-D devices. Subjects in the No Implant Attempt, Unsuccessful Implants, CRT-D: Not Randomized, and all CRT-P subgroups were excluded.

Arm	Measure	Group	Value (NUMBER)
Biventricular Pacing Arm	Incidence of Ventricular Tachyarrhythmias	Subjects who experienced VT/VF	39 participants
Biventricular Pacing Arm	Incidence of Ventricular Tachyarrhythmias	Subjects who did not experience VT/VF	67 participants
Right Ventricular Pacing Arm	Incidence of Ventricular Tachyarrhythmias	Subjects who experienced VT/VF	31 participants
Right Ventricular Pacing Arm	Incidence of Ventricular Tachyarrhythmias	Subjects who did not experience VT/VF	70 participants

Comparison: The null hypothesis is that patients with AV block, ejection fractions of at most 50%, NYHA classifications of I-III, and indicated for defibrillation therapy who receive biventricular (BiV) pacing have the same rate of experiencing their first ventricular arrhythmia as corresponding patients who receive right ventricular pacing. This was tested against the one-side hypothesis that patients with BiV pacing have a lower risk of ventricular arrhythmias than subjects with right ventricular pacing.p-value: 0.18995% CI: [0.78, 2.01]Posterior Distribution for HR

Source: ClinicalTrials.gov · Data processed: Mar 23, 2026

Biventricular Versus Right Ventricular Pacing in Heart Failure Patients With Atrioventricular Block (BLOCK HF)

Conditions

Keywords

Brief summary

Related papers

Interventions

Sponsors

Study design

Eligibility

Inclusion criteria

Exclusion criteria

Design outcomes

Primary

Secondary

Countries

Participant flow

Participants by arm

Withdrawals & dropouts

Baseline characteristics

Adverse events

Outcome results

Mortality, Heart Failure-related Urgent Care Visits, or Significant Increase in Left Ventricular End Systolic Volume Index (LVESVI)

All-Cause Mortality

All-Cause Mortality or Heart Failure-related Hospitalization

All-Cause Mortality or Significant Increase in Left Ventricular End Systolic Volume Index

Cardiovascular-related Healthcare Utilizations

Change in Cardiac Index From Randomization to 12 Months

Change in Cardiac Index From Randomization to 18 Months

Change in Cardiac Index From Randomization to 24 Months

Change in Cardiac Index From Randomization to 6 Months

Change in Cardiovascular Medications

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 12 Months

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 18 Months

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 24 Months

Change in E Wave/A Wave Ratio (E:A Ratio) From Randomization to 6 Months

Change in Heart Failure Stage

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 12 Months

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 18 Months

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 24 Months

Change in Interventricular Mechanical Delay (IVMD) From Randomization to 6 Months

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 12 Months

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 18 Months

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 24 Months

Change in Left Ventricular Ejection Fraction (LVEF) From Randomization to 6 Months

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 12 Months

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 18 Months

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 24 Months

Change in Left Ventricular End Diastolic Dimension (LVEDD) From Randomization to 6 Months

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 12 Months

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 18 Months

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 24 Months

Change in Left Ventricular End Diastolic Volume Index (LVEDVI) From Randomization to 6 Months

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 12 Months

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 18 Months

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 24 Months

Change in Left Ventricular End Systolic Dimension (LVESD) From Randomization to 6 Months

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 12 Months

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 18 Months

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 24 Months

Change in Left Ventricular End Systolic Volume Index (LVESVI) From Randomization to 6 Months

Change in Left Ventricular Mass (LV Mass) From Randomization to 12 Months

Change in Left Ventricular Mass (LV Mass) From Randomization to 18 Months

Change in Left Ventricular Mass (LV Mass) From Randomization to 24 Months

Change in Left Ventricular Mass (LV Mass) From Randomization to 6 Months

Change in Mitral Regurgitation From Randomization to 12 Months

Change in Mitral Regurgitation From Randomization to 18 Months

Change in Mitral Regurgitation From Randomization to 24 Months

Change in Mitral Regurgitation From Randomization to 6 Months

Change in New York Heart Association Classification

Change in Quality of Life at 12 Months

Change in Quality of Life at 18 Months

Change in Quality of Life at 24 Months

Change in Quality of Life at 6 Months

Clinical Composite Score at 12 Months

Clinical Composite Score at 18 Months

Clinical Composite Score at 24 Months

Clinical Composite Score at 6 Months

CRT-P and CRT-D System Implant Success

Days Hospitalized for Heart Failure

First Heart Failure Hospitalization