Superimposition of transmural infarction following acute subendocardial infarction; how frequent?

Thirty-five consecutive patients with acute subendocardial infarction admitted to the coronary care unit during a 15-month period were identified and analyzed for location of infarction, and for the in-hospital course in terms of recurrent chest pain, the occurrence of a second infarction, and the clinical status at the end of hospitalization. Thirteen patients developed a transmural infarction sometime between 3 and 21 days (average, ten days) after the initial subendocardial infarction. The transmural infarction was defined by a separate episode of severe and prolonged chest pain, late development of QRS alteration, and an appropriate elevation of the creatine phosphokinase concentration. Our experience with acute subendocardial infarction, hertofore regarded as a relatively benign event, indicates that the immediate prognosis of the patient who sustains his first episode of subendocardial infarction is not at all benign, and, indeed, subendocardial infarction frequently heralds transmural infarction within the acute phase of the disease.