Quantitative Hemodynamic Effects of Heart Rate in Aortic Regurgitation

The hemodynamic effect of varying heart rate was studied in eight patients with aortic regurgitation. At the subjects' resting sinus rhythm and at a higher heart rate induced with right atrial pacing, left ventricular and aortic pressures and Fick cardiac outputs (FCO) were measured, and left ventricular biplane angiocardiograms were performed. Left ventricular volumes and left ventricular minute flow (LVMF) were determined from the angiograms. Regurgitant flow was quantitated by subtracting the FCO from LVMF. Increased heart rate produced highly significant reductions in the left ventricular end-diastolic pressure (LVEDP), left ventricular end-diastolic volume, and stroke volume. End-diastolic circumferential stress (EDCS) and end-diastolic load (EDL) were abnormally high at resting sinus rhythm and were markedly decreased with increased heart rate. FCO increased, but no significant changes were observed in either the LVMF or the regurgitant flow per minute.Bradycardia in aortic regurgitation may cause pulmonary congestion secondary to high LVEDP and may accelerate left ventricular dilatation secondary to markedly elevated EDCS and EDL. The possible benefits of preventing bradycardia in aortic regurgitation by chronic demand pacing is currently being tested.