Increased exercise tolerance and reduced electrocardiographic ischemia with diltiazem in patients with stable angina pectoris

Abstract

Diltiazem is a calcium slow-channel blocking drug that may be effective in the treatment of chronic stable angina pectoris. To evaluate the therapeutic efficacy 3 hours after a single oral dose of 120 mg, 12 men with chronic stable angina pectoris performed a maximal exercise test on a bicycle ergometer after ingesting either placebo or diltiazem administered in a double-blind fashion. During submaximal exercise at a fixed work load, diltiazem decreased the average heart rate response from 119 ± 17 to 107 ± 14 beats/min (p < 0.01), systolic blood pressure from 182 ± 15 to 175 ± 15 mm Hg (p < 0.05) and the rate-pressure product from 21.8 ± 4.2 to 18.8 ± 3.2 x 10-3 units (p < 0.01). The average submaximal work load at which significant ST-segment depression (0.1 mV) first appeared was increased from 355 ± 142 to 525 ± 143 seconds (p < 0.01) after diltiazem. At peak exercise after diltiazem, the average depth of ST-segment depression in any one lead and the extent of myocardial ischemia observed in all 12 ECG leads were decreased (p < 0.01), even though the average work load was increased by 29% (p < 0.01). Peak heart rate, systolic blood pressure and rate-pressure product were similar with placebo and diltiazem. The plasma diltiazem concentration was 139 ± 29 ng/ml 3 hours after ingestion and was significantly (p < 0.05) related to the increased time to the onset of important ST-segment depression (r = 0.65) and to the decrease in the extent of myocardial ischemia observed in all 12 ECG leads (r = -0.61) compared with placebo. Thus, diltiazem is effective in treating chronic stable angina pectoris. It decreases myocardial oxygen requirements during upright exercise and appears to increase myocardial oxygen delivery.