The detection of silent ischemia: cautions and precautions.

THERE IS NOW convincing evidence that myocardial ischemia may occur in the absence of symptoms.' This phenomenon, which has acquired the label "silent ischemia," is receiving considerable attention as a factor with potential prognostic significance in the management of coronary artery disease. Basic to an understanding of silent ischemia, its prevalence, precipitating factors, significance as a risk factor, and response to therapy, is knowledge of the effectiveness of the technologies used to detect it. Twenty-five years of developments in the theory and practice of laboratory test interpretation have contributed to the rational use of noninvasive tests for the diagnosis of coronary artery disease. The principles governing test interpretation so arduously derived over this time should be, but perhaps are not being, applied to the detection of myocardial ischemia as an entity unto itself. Since the implications for management inherent in the diagnosis of ischemia may differ from those emanating from the diagnosis of coronary artery disease, tests designed to detect myocardial ischemia should be interpreted with the effectiveness of the test for that purpose in mind, and transfer of information relative to the effectiveness of the test for the diagnosis of coronary artery disease to ischemia should not be done without consideration of the appropriateness of such a transfer. The tests that are used to evaluate patients with coronary artery disease can be divided into four categories (table 1): tests that assess the electrical consequences of coronary artery disease, such as stress and ambulatory electrocardiography; tests that assess myocardial perfusion; tests that assess contractile function; and tests that assess metabolic function. These tests