Vasovagal Syncope
Conditions
Keywords
pacemaker, stroke volume, cardiac output, heart rate
Brief summary
The investigators will seek to determine the effects of different heart rates on both stroke volume and cardiac output using non-invasive hemodynamic assessments. In order to safely manipulate the HR, the investigators will study patients with permanent pacemakers in whom heart rate manipulation can be done in a safe and non-invasive manner.
Detailed description
Permanent pacemakers have sometimes been used to treat patients with recurrent vasovagal syncope. This is because patients with vasovagal syncope often experience bradycardia at the time of their syncope. Unfortunately, pacemakers are often ineffective in preventing syncope. Classical cardiovascular hemodynamics would suggest that increasing the heart rate (HR; via pacemaker) should increase the cardiac output (CO). This is because: CO = HR x Stroke volume (SV). The assumption is that the SV is fixed during manipulation of the HR. However, this might not be the case. As the number of beats per minute (HR) increases, the cardiac cycle length (R-R interval \[RRI\]) shortens, as a function of simple math. This means that the time in cardiac systole shortens, and the time in cardiac diastole shortens. Since cardiac diastole is when the heart fills up with blood, faster HR can be associated with decreased cardiac filling times. This, in turn, could compromise the SV. However, there is a paucity of data as to what happens to SV and CO at different HR. Further, it is possible that these effects will be different when a person is lying down supine versus when a patient is upright (when stroke volume will be lower). The investigators will seek to determine the effects of different HR on both SV & CO. In order to safely manipulate the HR, they will study patients with permanent pacemakers in whom HR manipulation can be done in a safe and non-invasive manner.
Interventions
DEVICEPacing
Assess the non-invasively determined stroke volume and cardiac output response at different paced heart rates in patients with a cardiac pacemaker or implanted defibrillator with preserved ejection fractions (LVEF≥50%)
Sponsors
University of Calgary
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
Healthy volunteers
No
Inclusion criteria
* Age 18-70 years (inclusive) * Implanted permanent pacemaker or implanted defibrillator capable of atrial and ventricular pacing * LV ejection fraction \>50%
Exclusion criteria
* Unable or unwilling to provide informed consent * Clinical need for a cardiac resynchronization device
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in cardiac output while atrial pacing at lower and higher rates while supine | 1 day | Change in cardiac output (CO) when atrial pacing at 80 bpm & 120 bpm while supine. CO = HR x Stroke volume (SV) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright | 1 day | Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright at different paced rates |
| Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright | 1 day | Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright at different paced rates |
| Change in stroke volume at lower and higher atrial paced rates while tilted up | 1 day | Change in stroke volume at lower (50-70 bpm) vs. higher (130 bpm) atrial paced rates while tilted up |
| Change in cardiac output at lower and higher ventricular (VVI) paced rates while supine | 1 day | Change in Cardiac output at ventricular (VVI) paced rates when it is lower (50-70 bpm) and higher (130 bpm) while supine |
| Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright | 1 day | Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright at different paced rates |
| Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright | 1 day | Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright at different paced rates |
| Change in stroke volume at lower and higher ventricular (VVI) paced rates while tilted up | 1 day | Change in stroke volume at ventricular (VVI) paced rates when it is lower (50-70 bpm) and higher (130 bpm) while tilted up |
Countries
Canada
Contacts
Primary ContactSatish R Raj, MD MSCI
Outcome results
None listed