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.