The earliest electrocardiographic sign of acute transmural myocardial infarction.

A 43 year old man had serial 12-lead electrocardiograms (ECG) in the early phase of an acute anterior transmural myocardial infarction. In addition to the ST-segment elevation and hyperacute T waves, the patient's ECG displayed increase in the R wave voltage, decrease and final disappearance of the S wave, merging of the R wave with the elevated ST-segment and formation of monophonic curves. Such ECG patterns have been noted in the early phase of experimental coronary occlusion in the dog and in patients with Prinzmetal's angina. The clinical implication of this observation is discussed.