Postoperative myocardial infarction: a prospective study in a risk group of surgical patients.

Out of a total of 12,654 patients who underwent major surgery under general or regional anesthesia during a 3-year period, there were 12 postoperative myocardial infarctions in patients with no evidence of previous heart disease. From the same group of patients, a selected group of 214 patients with preoperative myocardial infarction or with ECG patterns suggesting left ventricular hypertrophy or subendocardial injury were studied preoperatively and reassessed by means of postoperative serial ECGs. Thirty-eight of these patients (17.7%) developed postoperative myocardial infarction, 18 of whom had ECG patterns of transmural and 17 of subendocardial infarction. In three other patients who died from cardiac arrest, transmural infarction was verified at autopsy. Eighty-five percent of all infarctions were detected within the first 3 postoperative days. Sixteen infarctions (32%) were fatal. Excluding three fatal cardiac arrests, 13 (37%) of the other 35 infarctions in the series occurred without clinical symptoms. Risk factors associated with increased infarction rates included intraoperative hypotensive episodes, preoperative hypertension, and previous myocardial infarction within six months. Type of surgery, anesthetic techniques, anesthesia of more than 3 hours' duration, patient factors such as diabetes, a history of chest pain, and age and sex did not significantly affect the rate of infarction. Postoperative myocardial infarction is a rare complication in patients who have no evidence of previous heart disease. Preoperative recognition of ischemic ECG changes and other risk factors demands ECG tracing for at least 3 days after surgery.