IMPACT OF UNSTABLE ANGINA ON OPERATIVE MORTALITY WITH CORONARY REVASCULARIZATION AT VARYING TIME INTERVALS AFTER MYOCARDIAL-INFARCTION

We have performed a retrospective study of patients undergoing coronary artery bypass grafting for postinfarction angina in an effort to determine the influence of recency of myocardial infarction and unstable angina on operative mortality. Time from myocardial infarction to bypass was arbitrarily divided into five intervals. Nine hundred ninety-three patients having isolated coronary bypass for postinfarction angina were analyzed, and a significant trend of increased operative mortality with recency of myocardial infarction was found (p < 0.001). When patients were operated on during the time interval zero to 24 hours after infarction, the operative mortality rate was 18.6%. In the interval from 1 day to 1 week after infarction, the operative mortality rate was 7.4%; 1 week to 3 weeks, 5.9%; and 3 weeks to 3 months, 2.7%. In patients operated on more than 3 months after infarction, the operative mortality rate was 3.9%. The operative mortality rate in 360 patients with postinfarction stable angina was 0.83% compared with 7.3% in 633 patients with postinfarction unstable angina (p < 0.001). Of 18 risk factors tested, 12 were found by univariate analysis to be independent predictors of operative mortality, including recency of myocardial infarction and unstable angina. Stepwise logistic regression analysis of independent predictive variables revealed that unstable angina, previous surgical revascularization, preoperative hypotension, nonelective surgery, preoperative cardiac arrest, and female sex were the strongest predictors of mortality; recency of myocardial infarction was not a factor. When acute surgical reperfusion is not the primary treatment strategy for patients with myocardial infarction, operative mortality with coronary bypass is increased with the recency of myocardial infarction. The reason for this increase in operative mortality is a patient selection process in which those with persistent or intermittent myocardial ischemia, as reflected in the clinical syndrome of unstable angina, are selected for operation. Unstable angina is a major determinant of operative mortality after myocardial infarction. In patients with stable angina, operative mortality is not increased by the recency of myocardial infarction.