Effect of experimentally induced atrial fibrillation on coronary circulation in dogs

Summary The influence of atrial fibrillation on coronary circulation was studied in 21 anesthetized open-chest dogs. Atrial fibrillation was induced either by local application of acetylcholine (10% in normal saline) on the left atrial appendage or by electric stimulation (2–7 volts, 2 ms, 50 Hz). When atrial fibrillation was induced (n=10), mean aortic pressure fell and heart rate rose significantly; coronary blood flow (CBF) remained unchanged (78±6 vs. 75±5 ml/min×10 g) while coronary vascular resistance (CVR) (1.16±0.05 vs. 0.87±0.07 [mHg×min×100 gl/ml [RU], p<0.0001) and sinus oxygen saturation (26±2 vs. 22±1%, p<0.05) decreased. Following the application of carbochromen (5 mg/kg in 3 min i.v.) resulting in maximal coronary dilatation, atrial fibrillation resulted in a reduction in CBF (311±48 vs. 205±30 ml/min×100 g, p<0.01) and coronary sinus oxygen saturation (65±6 vs. 42±6%, p<0.01), while CVR (0.27±0.03 vs. 0.37±0.04 RU, p<0.0001) was 38±8% (p<0.0005) higher during atrial fibrillation than at sinus rhythm.