Female sex as an independent predictor of morbidity and survival after isolated coronary artery bypass grafting

Background. This study sought to determine whether female sex was an independent risk factor for combined in-hospital morbidity, mortality, and long-term survival after coronary artery bypass grafting (CABG).

Methods. Data were collected prospectively for 1,114 (23.5%) women and 3,628 (76.5%) men operated on between January 1, 1996 and December 31, 2004 with median follow-up of 7.9 years (interquartile range 3.55 to 10.5). The combined morbidity end point was defined as in-hospital renal failure, stroke, ventilation for more than 24 hours, deep sternal wound infection, reoperation, myocardial infarction (MI), and mortality less than 30 days after discharge. The long-term all-cause and cardiac mortality outcomes were analyzed using multivariate proportional hazard regression.

Results. Females were older, with lower body surface area, and generally had more significant comorbid conditions than did males (p < 0.05). Female sex was associated with increased odds of the combined morbidity end point (adjusted odds ratio [OR] = 1.29; 95% confidence interval, 1.04 to 1.59, p = 0.02). There were 868 deaths (18.3% of total sample) during the follow-up period, and 305 deaths (n = 305 [35.1%] of deaths) were deemed to be of cardiac causes. In adjusted survival models, female sex was associated with cardiac mortality (hazard ratio [HR] = 1.28; 95% confidence interval, 0.96 to 1.73; p = 0.10) but not with all-cause mortality (HR = 0.92; 95% confidence interval, 0.77 to 1.11; p = 0.38).

Conclusions. Female sex was associated with early combined morbidity and long-term cardiac mortality but not long-term all-cause mortality. A greater proportion of concomitant risk factors characterize female patients undergoing CABG.