Myocardial ischemia: detection and quantitation.

Myocardial ischemia at rest occurs only late in the course of coronary artery disease, but transient ischemia can often be induced by increasing myocardial oxygen demand with exercise or atrial pacing. Myocardial ischemia causes a series of physiologic abnormalities that can be detected by assessment of myocardial perfusion, regional mechanical function, electrophysiology, and metabolism. Methods of assessment vary widely in sensitivity, specificity, cost, and ease of application. Although the appropriate choice of diagnostic test may be difficult, the morbidity and mortality that result from myocardial ischemia and infarction and the demonstrated potential of coronary artery bypass surgery to reverse myocardial ischemia before the development of permanent sequellae make the detection of ischemia an important clinical problem. Present methods for quantitating myocardial ischemia are imprecise and difficult to apply but have been used successfully to evaluate the efficacy of therapies designed to reduce the size of myocardial infarction.