Changes occurring in the postinfarction ECG in relation to age, sex, and previous myocardial infarction.

Minnesota codes (MC), expressing Q-QS, ST segment, and T wave abnormalities in ECGs taken during the acute event and at a 1-year follow-up were studied in 256 survivors of myocardial infarction (MI). On the 1-year ECGs large Q waves (MC 1.1) were more common in patients with a history of previous MI than in those with a first MI. Regression of Q-QS, ST segment, and T wave changes occurred more extensively in first MIs, whereas progression of MC Q-QS and ST segment signs tended to be common in those with recurrent MI. On the acute ECGs large Q waves were more frequent in men (52%) than in women (36%), but ST segment depression of 1 mm or more (MC 4.1) was predominant in women in both the acute and 1-year ECGs. This ECG sign was related to the advanced age of the patients. There was no significant sex difference in the regression of the Q-QS signs, but the disappearance of ST and T wave changes occurred more extensively in men. The ECG returned to normal in 12% of men with a first MI but only infrequently in women and men with recurrent MI.