Sudden disappearance of electrocardiographic pattern of anteroseptal myocardial infarction. Result of superimposed acute posterior myocardial infarction.

In a 76-year-old man an electrocardiographic pattern of acute anteroseptal myocardial infarction disappeared suudenly. At necropsy, a more recent posterior myocardial infarct was found, in addition to an acute anteroseptal infarct. "Normalization" of the electrocardiogram from the pattern of anteroseptal myocardial infarction in this case resulted from the loss of opposing electromotive forces in the posterior wall because of posterior infarction.