Noninvasive assessment of acute effects of nifedipine on rest and exercise hemodynamics and cardiac function in patients with aortic regurgitation.

The acute effects of nifedipine (20 mg sublingually) on hemodynamics and cardiac function were studied at rest and during supine bicycle exercise in 20 patients with aortic regurgitation. At rest, heart rate increased by 13%, systemic vascular resistance decreased by 34% and regurgitant index decreased by 17%. The change in systemic vascular resistance was related to its initial rest level (r = 0.82, p less than 0.001) and to the changes in forward cardiac output (r = 0.58, p less than 0.01) and regurgitant index (r = 0.60, p less than 0.01). Left ventricular end-diastolic and end-systolic volumes, stroke volume and ejection fraction were unchanged, whereas right ventricular ejection fraction increased. During exercise, nifedipine administration further increased heart rate by 8% and decreased systemic vascular resistance by 19%. Both forward stroke volume and forward cardiac output increased, but total left ventricular stroke volume was unchanged, resulting in a significant decrease in regurgitant index. Although left ventricular end-diastolic volume was slightly decreased, end-systolic volume did not increase; thus, ejection fraction was higher than that during control exercise (p less than 0.01). Right ventricular ejection fraction increased further. In aortic regurgitation, the acute administration of nifedipine improved cardiac performance and reduced regurgitation at rest and during exercise as a result of afterload reduction and increased heart rate. Whether these beneficial effects will occur during long-term therapy requires further investigation.