THE ELECTROCARDIOGRAPHIC DIAGNOSIS OF ACUTE MYOCARDIAL ISCHEMIA

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Abstract
By correlation of "spontaneous" S-T changes in serial ecg with autopsy findings, the pseudode-pression associated with tachycardia with exaggeration of the Tp wave is distinguished from abnormal depression secondary to acute subendocardial injury. In the former the S-T segment displays a continuous ascent in a curve with upward concavity; in the latter it exhibits a characteristic horizontal or sagging depression of 1 mm or more in the absence of cardiac glyco-sides. Both the Levy and Master tests were used extensively for the induction of ecg changes; the latter method is preferred. It is employed for diagnostic purposes when there is a suspicion but no clear-cut evidence of coronary insufficiency; it is utilized for prognostic purposes in asymptomatic ambulatory patients after recovery from myocardial infarction to evaluate tolerance of prescribed activity. Changes in the S-T segment of the resting ecg that might have formed the basis for the prediction of abnormal tests are emphasized. Abnormal S-T displacements are much more frequent in leads V4,5, and may be associated with septal ischemia; evidence localized to back leads and/or aVF may be associated with posterior ischemia. Standard limb leads are not positive nearly so frequently as the chest leads and showed no abnormalities that are not better evaluated by multiple chest leads.