Mixed ischemic subsets. Comparison of the mechanisms of silent ischemia and mixed angina.

The traditional concept of myocardial ischemia precipitated by increases in the myocardial demand for oxygen is well accepted for patients with fixed coronary atherosclerosis. Recently, however, observations of abnormal vasomotor tone in the coronary artery bed have suggested that vasoconstriction at an atherosclerotic site may be a primary cause of decreases in the myocardial supply of oxygen. This has led to a classification of mixed ischemic subsets characterized by the superimposition of an increased myocardial oxygen demand on a decreased myocardial oxygen supply. The subsets are defined by several clinical parameters, including unstable angina pectoris, acute myocardial infarction, malignant ventricular arrhythmias, mixed angina pectoris, and asymptomatic or silent ischemia. Holter monitoring, electrocardiography, and evaluations of wall motion have confirmed the existence of asymptomatic ischemic episodes that far outnumber episodes of angina in patients with stable angina pectoris. This concept has considerable diagnostic and therapeutic implications.