Is silent myocardial ischemia clinically important? Does it have prognostic significance?

The precise mechanism responsible for silent myocardial ischemia has not been established, but available data suggest that both an increase in oxygen demand and a decrease in coronary blood flow may be responsible. Studies indicate that more than 60 minutes of silent ischemia during 24-hour ambulatory electrocardiographic monitoring correlates with an increased incidence of myocardial infarction, cardiac death, and recurrent symptoms requiring coronary revascularization. Even in patients with shorter, repeated episodes of silent ischemia, small areas of subendocardial necrosis may develop that eventually lead to progressive left ventricular dysfunction, which increases the risk of subsequent mortality. Antianginal therapy, even though effective in control of symptoms, does not abolish silent ischemia. Further study of the pathogenesis of silent ischemia is needed before an effective treatment plan can be established.