Effect of perioperative complications on excess mortality among women after coronary artery bypass: The Israeli coronary artery bypass graft study (ISCAB)

Background: Widely observed excess mortality among women after coronary artery bypass grafting is still largely unexplained, although case-mix factors have been identified. We evaluated the contribution of perioperative complications to the risk of 180-day mortality among women while adjusting for case-mix factors. Methods: This is part of a prospective, 1-year nationwide Israeli coronary artery bypass graft study of 1029 female and 3806 male patients. Deaths within 180 days were independently ascertained. Case-mix risk strata were obtained from a pooled Cox survival model (including all subjects and study variables) by using the adjusted coefficients corresponding to the case-mix factors within the model. Sex-specific mortality associated with perioperative complications was evaluated within the strata. In addition, sex-specific Cox models were constructed. Results: Higher mortality among women compared with that among men was significant within the pooled model (hazard ratio, 1.4; P = .038) and was evident early in the postoperative period. Women tended to cluster in the highest risk quartile compared with men (39.8% vs 20.9%, P < .001). However, although the incidence of perioperative complications was similar for the 2 sexes, the associated mortality for a given perioperative complication was higher among women. Sex-specific Cox models confirmed the above findings. For example, the hazard ratio for women with low postoperative hemoglobin was 6.9, whereas for men, the hazard ratio was 3.9. Conclusions: The role of perioperative factors in the excess mortality among women after coronary artery bypass grafting shifts the focus of attention from the selection of women for the operation to the in-hospital experience. Improving the outcome for women will entail efforts to prevent complications in the perioperative period.