The Effects on Left Ventricular Performance of Nifedipine and Verapamil in Exercise-induced Angina Pectoris

The differences between slow calcium blocking agents with respect to effects on heart rate, myocardial contractility and atrioventricular conducting time are well described; the relevance of such differences to the treatment of patients with impaired left ventricular function due to coronary heart disease is uncertain. The haemodynamic effects of equivalent hypotensive doses of nifedipine and verapamil were therefore compared in 20 patients with severe angina pectoris associated with angiographically documented coronary artery disease. The plasma concentrations of nifedipine (mean 57 +/- 19; range 27-77 ng/ml) and verapamil (mean 147 +/- 14; range 117-260 ng/ml) at the time of the haemodynamic measurements were of an order usually associated with substantial pharmacodynamic activity. Sitting at rest nifedipine resulted in reduction in systemic arterial pressure (P less than 0.05) and vascular resistance (P less than 0.01); both the heart rate (P less than 0.01) and cardiac output (P less than 0.05) increased without any significant change in the left heart filling pressure. In contrast, verapamil, which similarly reduced systemic blood pressure (P less than 0.05) and vascular resistance (P less than 0.01), increased cardiac output (P less than 0.05) and left heart filling pressure (P less than 0.05) without any change in heart rate. During upright bicycle exercise both drugs attenuated the angina induced in all subjects during the control exercise period. Despite reductions in systemic blood pressure and vascular resistance the cardiac output was unaltered on either drug at the same workload as in the control assessment. The reduction in exercise blood pressure following nifedipine induced a reflex tachycardia; this was not present, despite the similar hypotensive action, after verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)