Improved exercise performance in persons with stable angina pectoris receiving diltiazem

The effects of diltiazem, a calcium antagonist drug, were compared with those of placebo on exercise performance during a series of symptom-limited upright exercise tests. Ten patients with chronic stable angina were studied over a period of 7 weeks. The drug was administered in a random double-blind fashion and was evaluated at increasing dose levels of 120, 180 and 240 mg/day. Diltiazem was effective in increasing the total duration of exercise (p <0.001) and the time to the first onset of angina (p <0.02) and to the first appearance of 1 mm of S-T depression (p <0.02). These effects were most marked at the highest dose level of diltiazem. The heart rate was reduced at rest (p <0.05) and during submaximal exercise (p <0.001). There was a reduction in diastolic blood pressure during submaximal exercise (p <0.04) but no change in systolic pressure. Pressure-rate product was significantly reduced at submaximal (p <0.001) but not maximal exercise. The reduction in pressure-rate product is postulated as the mechanism by which diltiazem enhances duration of exercise. There was no reduction in electrocardiographic evidence of myocardial ischemia at peak exercise by either clinical observation or computer analysis of spatial electrocardiographic variables. Five of the six patients who continued to take the drug maintained or improved their exercise performance on follow-up study 8 to 10 months later.