[Influence of cardiac pacing on graft flow following aortocoronary bypass surgery--comparison of ventricular and atrial pacing].

To evaluate the influence of cardiac pacing on hemodynamics and graft flow dynamics following aortocoronary bypass surgery, we measured vein graft flow, systolic and diastolic graft flow volume along with blood pressure and cardiac output during atrial and ventricular pacing in 20 patients, 26 grafts. During ventricular pacing, systolic blood pressure showed a significant decline of 17% at the minimum pacing rates (101 +/- 9/min), 17% and 21% at the pacing rates of 120 and 140, respectively (p less than 0.01) in comparison with the original heart rates (96 +/- 8/min). The cardiac output also decreased significantly (p less than 0.01) during ventricular pacing. Graft flow at the original heart rates was 86 +/- 22 ml/min and the graft flow at the minimum pacing rates, at the pacing rates of 120 and 140 decreased to 73 +/- 20, 75 +/- 21, 74 +/- 23 ml/min (P less than 0.01), respectively. These reduction in the graft flow were caused by a decrease in diastolic graft flow (p less than 0.01). In the patients with a history of myocardial infarction, ventricular pacing brought about much more decrease in blood pressure, cardiac output and graft flow volume than those in patients without myocardial infarction (p less than 0.01). During atrial pacing, no significant change was observed in blood pressure and cardiac output. The graft flow was 86 +/- 21 ml/min at the original heart rates and it increased to 93 +/- 24 at the pacing rates of 120 and 95 +/- 26 ml/min at the pacing rates of 140 (p less than 0.01). These increase in graft flow during atrial pacing were attributable to an increase in diastolic graft flow (p less than 0.05). These findings suggest that the atrial pacing following aortocoronary bypass surgery brings about the beneficial effects on coronary perfusion compared with ventricular pacing.