Perioperative myocardial infarction after coronary bypass surgery

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Perioperative myocardial infarction, a complication of coronary artery surgery, is an important clinical consideration because of its possible effects on long-term results.1–4 Variability from 5% to 40% in the reported frequency of perioperative myocardial infarction4 can be attributed to criteria for recognition of the event, technical factors, and differences in populations studied.

Electrocardiographic and enzyme data suitable for analyses were available for 1151 of 1638 patients having coronary artery bypass surgery without scar excision operated upon between 1970 and 1975. We analyzed these data to determine whether the frequency of perioperative myocardial infarction has changed and to assess the clinical outcome after hospitalization of comparable patients with and without perioperative myocardial infarction. The incidence of perioperative myocardial infarction was assessed using 12-lead electrocardiograms obtained preoperatively, on the day of operation and on the first, second, third, and seventh days after surgery. On the basis of persistent S-T segment elevation, Q wave changes and serum glutamic oxaloacetic transaminase (SGOT) greater than 100 IU/liter, we separated the surgical patients into groups according to their probability for perioperative myocardial infarction.

Using these criteria, we observed a decline in the incidence of the combined categories, definite and probable myocardial infarction, from 10%-14% in 1970–1972 to 2%–4% for 1974–1975. Preliminary data from 1976 show the perioperative myocardial infarction rate has remained at the same level for 1974–1975. The change is unlikely to be due to population differences. This reduction has occurred despite an increase in the mean number of grafts inserted . . .