Background: Female gender is a risk factor for early mortality after coronary artery bypass graft surgery (CABG). Yet, the causes for this excess mortality in women have not been fully explained.
Objectives: To analyse gender differences in early mortality (30 days post surgery) after CABG and to identify variables explaining the association between female gender and excess mortality, taking into account preoperative clinical and psychosocial, surgical and postoperative risk factors.
Methods: A total of 1,559 consecutive patients admitted to the German Heart Institute Berlin (2005-2008) for CABG were included in this prospective study. A comprehensive set of prespecified preoperative, surgical and postoperative risk factors were examined for their ability to explain the gender difference in early mortality.
Results: Early mortality after CABG was higher in women than in men (6.9 vs. 2.4 %, HR 2.91, 95 % CI 1.70-4.96, P < 0.001). Women were older than men (+4.7 years, P < 0.001), had lower self-assessed preoperative physical functioning (-16 points on a scale from 0 to 100, P < 0.001), and had higher rates of postoperative low cardiac output syndromes (6.6 vs. 3.3 %, P = 0.01), respiratory insufficiency (9.4 vs. 5.3 %, P = 0.006) and resuscitation (5.2 vs. 1.8 %, P = 0.001). The combination of these factors explained 71 % of the gender difference in early mortality; age and physical functioning alone accounted for 61 %. Adjusting for these variables, HR for female gender was 1.36 (95 % CI 0.77-2.41, P = 0.29).
Conclusions: Age, physical function and postoperative complications are key mediators of the overmortality of women after aortocoronary bypass surgery. Self-assessed physical functioning should be more seriously considered in preoperative risk assessment particularly in women.