Theoretical considerations in the use of calcium entry blockers in silent myocardial ischemia.

Asymptomatic myocardial ischemia likely results from an imbalance between myocardial oxygen supply and demand. Although changes in coronary vasomotor tone probably are important in the genesis of asymptomatic ischemia, heart rate increases also play a critical role. Consequently, all three classes of antianginal agents, nitrates, beta-blockers, and calcium entry blockers, have been shown efficacious as monotherapy for silent ischemia. Comparative studies have demonstrated that agents or combination therapies that control heart rate increases during normal activities are superior to regimens that increase average heart rate. Consideration of the side-effect profile of any therapy for asymptomatic patients also is important. The ideal therapy would be with one drug that reduced coronary vasomotor tone and myocardial oxygen demand during normal activities and had no adverse effects. Currently, the calcium entry blockers, diltiazem and verapamil, most closely approximate this ideal. It has yet to be proven, however, that the treatment of asymptomatic myocardial ischemia improves the prognosis of patients with coronary artery disease, and the risk-benefit ratio of pharmacological therapy is not established.