Long-term study of high-dose diltiazem in chronic stable exertional angina.

The efficacy of a calcium slow channel-blocking drug, diltiazem (360 mg/day), was compared to placebo in 15 men with exertional angina during a 21-week study. Symptom-limited exercise testing was used to evaluate the effects of the drug. Analysis of variance indicated the increase in the values of three time-related variables, time to onset of angina, time to onset of 1 mm ST depression, and total duration of exercise, were highly significant (all p less than 0.001). The increase from the second week of placebo to the last week of diltiazem was 4 X 1 minutes for time to angina, 2 X 4 minutes for time to 1 mm ST depression, and 2 X 3 minutes for total duration. In addition, the differences between mean values of these variables for placebo and corresponding diltiazem period at weeks 3 and 4 were significant (p less than 0.01, p less than 0.01, p less than 0.05) and for diltiazem week 20 and placebo week 21 were significant (p less than 0.005, p less than 0.01, p less than 0.005). Weekly angina frequency was reduced from a mean of 17 episodes/week during placebo to one episode/week during diltiazem (p less than 0.001). Submaximal pressure-rate product was reduced significantly during diltiazem (p less than 0.001), and the ECG evidence of myocardial ischemia was reduced by diltiazem at submaximal (p less than 0.02) and maximal exercise (p less than 0.001). The drug was well tolerated and appears to be effective monotherapy for exertional angina.