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

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 less than 0.01), systolic blood pressure from 182 +/- 15 to 175 +/- 15 mm Hg (p less than 0.05) and the rate-pressure product from 21.8 +/- 4.2 to 18.8 +/- 3.2 x 10(-3) units (p less than 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 less than 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 less than 0.01), even though the average work load was increased by 29% (p less than 0.01). Peak heart rate, systolic blood pressure and rate-pressure product were similar with placebo and diltiazem. The plasma diltiazem concentration was 13.9 +/- 29 ng/ml 3 hours after ingestion and was significantly (p less than 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.