Silent ischemia: a timely aspect in coronary artery disease.

The phenomenon of silent myocardial ischemia is defined as a transient alteration in myocardial perfusion, function or electrical activity in the absence of chest pain or the usual anginal equivalents. Patients may be classified as having one of three types of silent ischemia: type 1-asymptomatic with no history of myocardial infarction or angina; type 2-asymptomatic with previous myocardial infarction; type 3-angina is present in addition to asymptomatic ischemic episodes. Based on exercise testing, silent ischemia has been found in 2.5% of asymptomatic middle-aged men; a substantial number of such subjects subsequently incur cardiac events. In patients with type 2 silent ischemia, post-infarction mortality appears markedly higher than in cohorts without silent ischemia. In type 3 patients, 75 to 80% can be found to have silent ischemic episodes in addition to typical anginal attacks, the frequency of which may be up to three or four times that of the latter counterpart. In persons with coronary artery disease who succumb to sudden cardiac death, 25% have never had clinical symptoms suggesting that there may be a great number of persons with silent disease in the population at large.