Work up to rule out perioperative myocardial infarction: is it overused?

The awareness of the diagnostic difficulty and the documented high mortality risk of perioperative myocardial infarction (PMI) has led to the wide use of work up to rule out PMI after major noncardiac operations. This has caused stable postoperative patients to be kept in monitored hospital beds for extended periods of time and to be subjected to additional tests. We hypothesized that the mortality of PMI is high and, therefore, the wide use of postoperative work up to identify these patients is justifiable. We performed the following study to prove our hypothesis. All patients in the recovery room after major noncardiac operations who underwent work up to rule out PMI were identified and followed. The PMI work up included care in an electronically monitored unit, physical assessment, continuous ECG monitoring, and three 12lead electrocardiograms and cardiac enzymes obtained at six to eight hour intervals. Data collection included patient demographics; preoperative cardiac risk factors; incidence of intraoperative hypotension, hemorrhage and ECG changes; type of anesthesia and operative procedures and their durations; postoperative ECG and cardiac enzyme results; the incidence of PMI and patient outcome. Two hundred patients were studied; 85 males and 115 females. Their mean age was 62.9 years. Preexisting conditions included hypertension in 162 patients, peripheral arterial disease in 102, diabetes mellitus in 97, angina in 30, previous myocardial infarction in 41, and smoking in 107. Of 200 patients, 164 had an abnormal preoperative ECG. Vascular operations were performed in 104 patients, nonvascular abdominal operations in 48, and other operations in the remaining 48. Intraoperatively, hypotension occurred in 29 patients, blood loss of >500 ml in 25 and ECG changes in 10. There were no deaths. PMI occurred in 5/200 (2.5%) patients. Four had undergone vascular operations and one had had an abdominal operation. The mean age of the patients with PMI was 64.2 years. The duration of operation and blood loss were similar to those of patients without PMI. None of these patients developed cardiac failure or cardiogenic shock and none of them died.