The exercise tolerance test is the most important of all widely employed office techniques for the detection and evaluation of coronary arteriosclerosis. A reliable sign of coronary insufficiency is the S-T segment abnormality occurring in the postexercise electrocardiogram indicating ischemia. The S-T segment shift refers to a horizontal flattening or sagging depression of the S-T segment induced by exercise. The depressions occur most often in lead V4 or similar apical leads. They are produced usually by an amount of exercise equivalent to the double Master "two-step" exercise test, persist for more than one minute after the cessation of exercise, and are seen more easily with the patient in the supine position. The test is only reliable when the patient has not received digitalis for three weeks or quinidine for 24 hours prior to the test, or when hypokalemia, hypocalcemia, or hyperventilation are not present.
The test can be interpreted
Winsor T. The Electrocardiogram and Coronary Insufficiency. JAMA. 1968;203(1):43. doi:10.1001/jama.1968.03140010045011
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