Determinants of operative mortality following primary coronary artery bypass surgery

Background: The purpose of this study was to determine the factors which can help to predict operative mortality before performing the operation, and afterwards. Methods: The study population consisted of 504 patients (91 women and 413 men) who underwent primary isolated coronary artery bypass surgery from December 1997 to September 1999 by the same surgeon in a referral center in Tehran, Iran. Perioperative data were gathered and analyzed both in a univariate and multivariate model. Results: After the operation patients spent 7.3±4.0 days in hospital. The total operative morbidity was 20.5%. Arrhythmias were the most common complication, with atrial fibrillation as the predominant feature. Major complications of the operation were: low cardiac output (4.2%); prolonged ventilatory support (2.4%); hemorrhage and exploratory reoperation (2.0%); postoperative myocardial infarction (1.4%); postoperative renal failure in (1.4%); and postoperative cerebrovascular accident (0.8%). Operative mortality rate in this study was 2.98%. Factors associated with high operative mortality in univariate analysis were: recent myocardial infarction, low ejection fraction, non-elective operation, left main coronary artery disease and prolonged cardiopulmonary bypass time. Conclusion: Our data suggest that prior to operation, operative mortality can be best predicted by urgency of operation and left ventricle ejection fraction. After performing the operation, prognostic factors include preoperative LVEF≤35%, non-elective operation, and prolonged cardiopulmonary bypass time. Further study is required to assess the generalization of our findings to Iranian patients.