Exercise electrocardiography.

Treadmill exercise electrocardiography is a test commonly employed to diagnose coronary artery disease and has powerful prognostic value. It is most accurate when the resting ECG is normal, and because of significant limitations in sensitivity and specificity, the test is most useful when the pretest probability of disease is in the intermediate range. The usual criterion for diagnosing myocardial ischemia is horizontal or downsloping ST-segment depression that measures > or = 1 mm (0.1 mv) 0.08 seconds after the J point, and the specificity of this finding is greatly enhanced by the patient's developing typical angina during the test. Sensitivity and/or specificity may be improved by modifications of the ECG-lead system, computer-assisted measurement of more complex exercise-test variables, using test scores that incorporate coronary risk factors, and by adding radionuclide or echocardiographic imaging modalities that assess myocardial perfusion and/or the metabolic or contractile consequence of myocardial ischemia, as well as the electrocardiographic and symptomatic ones.