Multi-modal Magnetic Resonance Imaging to Assess Cerebrovascular Function in Atrial Fibrillation Patients

Atrial fibrillation (AF) is associated with an increased risk of cognitive decline, dementia, and stroke. Low cerebral blood flow (CBF) and low cerebrovascular carbon dioxide reactivity (CVR CO2 ) are associated with poor brain health outcomes. In the current study we employed magnetic resonance imaging (MRI) to quantify resting CBF and CVR CO2 in patients with AF and age-matched normal sinus rhythm (NSR) controls. We hypothesised that both resting CBF and CVR CO2 would be lower in patients with AF. Patients with AF (n=11, 65±14 years, 2 women) and NSR (n=12, 63±9 years, 7 women) underwent arterial spin labelling (ASL) at rest, and blood oxygen level-dependent (BOLD) MRI during a single-step increase in partial pressure of carbon dioxide (measured by end-tidal carbon dioxide (P ET CO 2 )) induced by changing the fraction of inspired CO 2 to 5% (21% O 2 , balance N 2 ). Region of interest time courses were extracted with grey matter, middle cerebral artery, and posterior cerebral artery territory masks. CVR CO2 was defined as the percentage change (%Δ) in BOLD signal vs %Δ in P ET CO 2 . Baseline CBF was not different between NSR and AF in grey matter (62±17 vs. 58±10 ml/min/100g, respectively; p=0.226), middle cerebral artery (59±16 vs. 56±14 ml/min/100g; p=0.361) and posterior cerebral artery (61±17 vs 53±15 ml/min/100g; p=0.138) territories. BOLD-derived CVR C02 was not different between NSR and AF groups in grey matter (0.11±0.04 vs. 0.12±0.03 %ΔBOLD/%ΔmmHg, respectively; p=0.372), middle cerebral artery (0.09±0.04 vs. 0.10±0.03 %ΔBOLD/%ΔmmHg; p=0.405) and posterior cerebral artery (0.13±0.04 vs. 0.14±0.05 %ΔBOLD/%ΔmmHg; p=0.367) territories. Collectively, these pilot data suggest that MRI-derived cerebrovascular CO 2 responsiveness is not different in patients with AF and age-matched NSR controls that have similar resting CBF. Further investigations are required to extend these preliminary findings to a larger cohort to fully elucidate the effects of AF on cerebrovascular function. Support provided by the Royal Society of New Zealand Te Apārangi Marsden Fund (19-UOA-170). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.