None listed
Conditions
Brief summary
Atrial fibrillation is a common heart rhythm disorder, which increases the lifetime risk of cognitive impairment disorders. Traditionally this was ascribed to blood clots formed during episodes of atrial fibrillation lodging in the brain, however even patients taking anti-coagulants (blood-thinners) without any sort of clot-related stroke are more likely to suffer from dementia and cognitive decline. We propose that the brain blood vessel responsiveness is dysfunctional in atrial fibrillation. To test our hypothesis we will use advanced magnetic resonance imaging techniques to assess brain blood vessel responsiveness in atrial fibrillation patients and matched control participants who have a normal heart rhythm. We will also determine whether brain blood vessel function is rescued in atrial fibrillation after restoring the normal heart rhythm (with [clinically indicated] cardioversion or radiofrequency/ cryo-ablation). These studies will provide novel mechanistic insights into the influence of atrial fibrillation on brain blood vessel function, and may inform the development of therapeutic strategies to offset the insidious effects of atrial fibrillation on the brain.
Interventions
This is a non-therapeutic mechanistic physiological study.
It will study people with atrial fibrillation and healthy people with a normal heart rhythm. They will attend a single preliminary screening visit (~45 min) and a single MRI scan visit (~90 min).
A sub-set of people with atrial fibrillation will be asked to attend a second visit to complete the same assessments undertaken at the MRI scan visit up to 14 days after the restoration of sinus rhythm (clinically indicated). This sub-set wil
This is a non-therapeutic mechanistic physiological study. It will study people with atrial fibrillation and healthy people with a normal heart rhythm. They will attend a single preliminary screening visit (~45 min) and a single MRI scan visit (~90 min). A sub-set of people with atrial fibrillation will be asked to attend a second visit to complete the same assessments undertaken at the MRI scan visit up to 14 days after the restoration of sinus rhythm (clinically indicated). This sub-set will be selected based on participant inability to attend MRI scan visits. Assessments: Screening visit- MRI Safety Screening Form and Health Screening Questionnaires Delivered by a trained investigator. Delivered face-to-face. Delivered once. Takes 5-10 min to complete this paper form. Cognitive function will be assessed using a touch sensitive tablet device. Delivered by a trained investigator. Delivered face-to-face. Delivered once. Takes ~20 min to complete this assessment. MRI scan visit- Height, weight, and blood pressure Delivered by a trained investigator. Delivered face-to-face. Delivered once. Takes 5-10 min to complete this assessment. Measurement of cerebral blood flow and cerebral metabolic rate for oxygen using MRI Assessed under baseline/resting conditions, and during neurovacular coupling and CO2 reactivity testing described below. Takes ~10 min to complete this assessment. Delivered by a trained radiologist and investigator team. Delivered face-to-face. Neurovascular coupling test in MRI scanner Participants will view a black/white flickering radial checkerboard visual stimulus alternated with a neutral grey screen baseline. Delivered by a trained radiologist and investigator team. Delivered face-to-face. Delivered as 5 x ~30s exposures, separated by ~30 s. Procedure conducted once per visit. Cerebrovascular CO2 reactivity Participants alternate between breathing room air and a premixed gas mixture with a mildly elevated partial pressure of CO2 (5% CO2, 21% O2, balance N2) via a Douglas bag (~2 min). Delivered by a trained radiologist and investigator team. Delivered face-to-face. Procedure conducted once per visit. Cardiac MRI Conventional ECG-gated retrospective cine cardiac MRI acquisitions will be acquired parallel and perpendicular to the cardiac long-axis. Delivered by a trained radiologist and investigator team. Delivered face-to-face. Delivered once per visit. Takes ~15-20 min to complete.
Sponsors
University of Auckland
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Atrial fibrillation patients • Chronic AF established on ECG or Holter monitoring • Men and women • Aged 18 years and over A sub-set of atrial fibrillation patients will be studied before and after: • A clinical decision (i.e., unrelated to the research study) to attempt restoration of sinus rhythm with cardioversion or by radiofrequency/ cryo-ablation has been taken. Healthy sinus rhythm controls • Healthy control subjects in sinus rhythm • Not taking any prescription or over-the-counter medications (other than oral contraceptive pill) • Men and women • Aged 18 years and over
Exclusion criteria
• <18 years old • Normal contraindications for MRI (e.g., metallic implants) • Current use of oral nitrates • Hemodynamically significant valvular heart disease (e.g., stenosis, mechanical valve replacement) • Severe left ventricular systolic dysfunction • Recent acute coronary syndrome (<12 months) (e.g., MI, angioplasty, unstable angina) • Severe respiratory disease (e.g., chronic obstructive pulmonary disease) • Severe, uncontrolled type II diabetes (e.g., insulin dependent) • Current cancer diagnosis or complete remission <5 years • Connective tissue or inflammatory disease (e.g., rheumatoid arthritis, lupus) • Neurological / psychiatric disease (e.g., stroke, TIA, dementia, Parkisnon’s) • Current infection or pyrexial illness • Uncontrolled thyroid disorders • Hepatic or renal impairment (e.g., eGFR <60) • Current pregnancy • Current hormone replacement therapy • Current user of recreational drugs • Current abuser of alcohol • Current smoker • Body mass index < 18 kg/m2. • Underlying medical conditions, which in the opinion of the Investigator place the participant at unacceptably high risk for participating in the study • Inability to fully or appropriately participate in the study
Outcome results
None listed