Myocardial infarction after noncardiac surgery

Background: In this study, the authors intensively monitored isoenzyme and electric activity of the heart for the first 7 days after noncardiac surgery in a large group of patients at risk for postoperative myocardial infarction (PMI). Methods: After institutional review board approval and written informed consent were received, 323 patients, aged 50 yr or older, who had ischemic heart disease and presented for noncardiac surgery, were enrolled in this prospective, blinded study. after operation, patients had daily clinical assessments, electrocardiograms, and measurements of creatine kinase (CK), CK-2 (mass and activity), and Troponin-T on the operative night, twice daily on postoperative days 1-4, and then daily on days 5-7. A diagnosis of PMI was made if the total CK was > 174 U/l and in the presence of two of the following: (1) CK-2/CK (mass or activity) > 5%, (2) new Q waves lasting greater than or equal to 0.04 s and 1 mm deep in at least two contiguous leads, (3) Troponin-T was > 0.2 mu g/l or (4) a positive result of pyrophosphate scan. Results: Eighteen of the 323 patients (5.6%) had a PMI, of which 3 (17%) were fatal. Only 3 of 18 patients had chest pain, whereas 10 of 18 patients (56%) had other clinical findings. The electrocardiographic classification of the PMI was Q wave in 6, non-Q wave in 10, and indeterminate in 2. The PMIs occurred on the day of operation in 8, on day one in 6, on day two in 3, and on day four in 1 patient. Conclusions: This study determined that PMI was an early event, only occasionally associated with chest pain, and usually non-Q wave in nature.