Effect of diltiazem and propranolol on myocardial ischaemia during unrestricted daily life in patients with effort-induced chronic stable angina pectoris.

To examine the effect of diltiazem 60 mg thrice daily and propranolol 80 mg thrice daily on myocardial ischaemia during unrestricted daily life, we have studied 14 patients with established effort-induced chronic stable angina pectoris in a double-blind crossover study. Ambulatory electrocardiographic monitoring was performed using frequency modulated (FM) tape recorder after 2 weeks of placebo therapy and at the end of each 4 week treatment period for a minimum of 24 h. The mean (+/- SEM) number of episodes of ST-segment depression greater than 1 mm during placebo treatment were 97 +/- 28, and these fell to 54 +/- 27 during diltiazem treatment (p less than 0.05) and to 12 +/- 6 during propranolol treatment (p less than 0.02). The maximal depth of ST-segment depression in 24 h, which indicates the severity of the episode, was 3.3 +/- 0.4 mm during placebo, 2.5 +/- 0.2 mm during diltiazem (p less than 0.05), and 1.6 +/- 0.5 mm during propranolol (p less than 0.01). Both diltiazem and propranolol treatment produced significant reduction in the total area of ST-segment depression observed during 24 h. A uniform reduction in the mean heart rate during the 24 h was observed during propranolol therapy and not during diltiazem therapy. Both diltiazem and propranolol treatment improved indices of myocardial ischaemia during daily normal unrestricted life, as measured by ambulatory ST-segment monitoring in patients with established chronic stable angina pectoris. Their differing effects on heart rate suggest that they act by different mechanisms.