Risk factors for early and late mortality in surgical treatment of coronary artery disease

A total of 1025 patients who had coronary bypass surgery at the Surgical Department A, Rikshospitalet, Oslo, between 1982 and 1986, were analysed for factors associated with early mortality and long-term survival. The cumulative follow-up time accounted for 6553 patient-years; the median follow-up was 6.45 years and ranged from the day of admission to 10 years. In total, 31 patients (3%) died within 30 days of surgery. Some 30 possible risk factors were analysed. Univariate analysis followed by a multivariate analysis defined six independent risk factors for early mortality. These were lack of sinus rhythm, previous heart surgery, mitral regurgitation, left main stem stenosis, unstable angina, and an elevated left ventricular end-diastolic pressure. Estimation of attributable risk showed that these factors could identify all patients who died early. Independent risk factors for late death were: lack of sinus rhythm, resection of a left ventricular aneurysm, left main stem stenosis, New York Heart Association (NYHA) class IV on admission, an elevated end-diastolic pressure, and prolonged cross-clamping time. The attributable risk analysis showed that independent risk factors for total mortality explained only about half of the patients who died. This appeared to be because of the competing effect of non-cardiac mortality. Results of the study show that risk factors for early mortality are good indicators for the outcome of coronary artery bypass surgery, identifying all deaths, whereas long-term mortality cannot be predicted. Stratification of independent risk factors allows a better comparison of mortality in different centres, and also better quality control of bypass surgery.