Hemodynamics of pacing after aortic valve replacement and coronary artery surgery

The cardiovascular effects of atrial, ventricular, and sequential pacing at PR intervals of 175, 150, 125, and 100 msec were studied immediately following cardiopulmonary bypass in patients with aortic stenosis, aortic insufficiency, or coronary artery disease. Atrial pacing increased the cardiac output and mean arterial blood pressure only in the patients with coronary artery disease. Ventricular pacing consistently was associated with the lowest cardiac output and mean arterial blood pressure. Hemodynamic response to changing PR intervals was variable. Our results suggest that if augmentation of heart rate is required in the period immediately after bypass, atrial pacing should be used in preference to ventricular pacing. In the presence of second- or third-degree heart block when atrial stimulation is ineffective, sequential pacing with an individualized PR interval becomes the therapeutic choice.