Risk stratification and prognostic effects of internal thoracic artery grafting during acute myocardial infarction

Abstract

Surgeons are occasionally requested to perform coronary artery bypass grafting during acute myocardial infarction. We intended to test the safety of coronary artery bypass grafting and internal thoracic artery grafting early after myocardial infarction using the Society of Thoracic Surgeons database. The database was queried for isolated coronary artery bypass grafting less than 24 hours after a myocardial infarction from 2002 to 2008. By using multivariable logistic regression and classification trees, risk models were created to stratify this group of patients. The independent prognostic effect of internal thoracic artery grafting was examined using standard risk-adjusted mortality comparisons. A total of 44,141 patients were identified, with an overall operative mortality of 7.9%. Cardiogenic shock occurred in 21%, percutaneous coronary intervention within 6 hours before surgery was performed in 11%, myocardial infarction within 6 hours before surgery occurred in 37%, preoperative intra-aortic balloon pump was used in 50%, and internal thoracic artery grafting was performed in 79% of the patients. Myocardial infarction in less than 24 hours was associated with higher operative mortality (odds ratio, 3.25) and major morbidity (odds ratio, 2.54). Emergency/salvage status (odds ratio, 6.43), age more than 80 years (odds ratio, 4.07), dialysis (odds ratio, 3.08), and cardiogenic shock (odds ratio, 2.79) were independent mortality predictors. Patients with nonemergence salvage status, absence of cardiogenic shock, creatinine less than 1.5 mg/dL, and age less than 70 years represented 48% of the population and exhibited a lower mortality rate of 2%. Internal thoracic artery grafting was independently associated with a lower risk of mortality (odds ratio, 0.52; P<.0001) and did not seem to compromise outcomes. Coronary artery bypass grafting less than 24 hours after myocardial infarction carries a higher operative risk but can be performed safely in selected patients. Although confounding variables may exist, internal thoracic artery grafting was associated with improved outcomes. Internal thoracic artery use in this setting is less than ideal, and taking time to harvest internal thoracic artery grafts in patients with acute myocardial infarction might be encouraged.