Effect of acute atrial fibrillation on phasic coronary blood flow pattern and flow reserve in humans.

AIMS To assess the effect of experimentally induced atrial fibrillation on coronary flow in humans. METHODS AND RESULTS In 16 patients (10 men, mean age 43+/-13 years) with normal coronary vessels, baseline and hyperaemic blood pressure and Doppler phasic coronary flow velocity were measured, using a 0.014 inch intracoronary Doppler flow wire, during sinus rhythm, experimentally induced atrial fibrillation, and right atrial pacing at a similar heart rate to that during atrial fibrillation. Coronary flow velocity integral per minute increased significantly during both right atrial pacing and atrial fibrillation compared to sinus rhythm, but during right atrial pacing the increase was greater (85+/-43% vs 52+/-25%, P<0.001). This difference persisted even after correction for the product of heart rate and blood pressure (1.15+/-0.51 vs 0.97+/-0.46, respectively, P<0.02). In a further 12 paced patients (seven men, mean age 54+/-10 years) with complete atrioventricular block the induction of atrial fibrillation (atrial fibrillation with regular RR interval) caused no significant changes in coronary flow velocity variables. CONCLUSIONS Acute atrial fibrillation in humans causes an increase in coronary flow that is, however, insufficient to compensate for the augmented myocardial oxygen demand, mainly because of the irregularity in the ventricular rhythm that exists during atrial fibrillation.