Reduced risk of coronary artery bypass surgery for unstable angina during a 6-year period

OBJECTIVE: To assess the risk of early death or acute myocardial infarction in patients undergoing isolated coronary artery bypass surgery for unstable coronary artery disease. METHODS: Retrospective observational study of 853 patients operated on because of unstable coronary artery disease during 1990-1995. RESULTS: There were 5.9% deaths and 13.0% nonfatal infarctions < or =30 days. These figures declined during the observation period and were 2.6% and 6.2%, respectively, in 1995. The relative risk of early death or myocardial infarction was 50% less during 1994-1995 than during 1990-1991, after multivariate adjustment for several patient risk factors. The risk of death or infarction was almost twice as high in patients > or =50 years than in those < 50 years of age. Multivariate analysis showed that aortic-cross-clamp time > or =60 min, previous bypass surgery, pre-operative heart failure, emergency surgery, worse Braunwald class and non-use of an internal mammary artery graft were associated with an increased risk of death or infarction. Early mortality was 3.4% (24/702) in unstable patients without symptoms of congestive heart failure, who were not operated on emergently after failed percutaneous coronary intervention and had not had previous cardiac surgery. CONCLUSIONS: We observed a marked reduction of the risk of early death or myocardial infarction after surgery for unstable angina during the 6-year period 1990-1995. The risk reduction was not explained from operations performed on patients with less risk and indicates improved peri-operative patient management.