Silent myocardial ischemia: therapeutic implications.

Current concepts concerning the pathophysiology of acute myocardial ischemia are reviewed. The importance of intermittent, dynamic shifts in the diameter of the coronary artery lumen is emphasized. Traditionally, it has been thought that angina pectoris is the common clinical hallmark of myocardial ischemia. It is now apparent that asymptomatic episodes of myocardial ischemia may be occurring far more frequently than symptomatic episodes. Although the natural history of asymptomatic myocardial ischemia is still unknown, ischemia, even in an asymptomatic form, can have serious consequences. This suggests the need for a careful assessment of patients in whom ischemia has been detected. In truly asymptomatic patients, detection is usually fortuitous; in patients with known coronary arterial disease, asymptomatic episodes should be sought as part of a noninvasive cardiac investigation, using multiple-stage exercise treadmill testing and 24-hour ambulatory electrocardiographic monitoring. Suggestions are made for the management of asymptomatic myocardial ischemia in relation to three patient groups: (1) asymptomatic ischemia in patients known to have symptomatic ischemia as well, (2) asymptomatic ischemia in patients without symptoms at any time, and (3) asymptomatic ischemia in patients who have had myocardial infarction. Medical management includes the use of calcium channel blocking drugs, beta-adrenergic blocking drugs, and nitrates. Documentation of an inadequate coronary artery reserve or evidence of associated left main coronary artery disease indicates the need for either aortocoronary bypass graft surgery or percutaneous transluminal coronary angioplasty, depending on the condition of the coronary anatomy and the degree of ventricular function. Whatever mode of treatment is used, documentation of its effectiveness should always be determined by appropriate follow-up studies. Clinical studies of the natural history of asymptomatic myocardial ischemia and its management are urgently needed.