Prevalence of risk factors, and not gender per se, determines short- and long-term survival after coronary artery bypass surgery

Abstract

Objective: Much attention has been directed towards female gender as an independent risk factor for in-hospital mortality after coronary artery bypass grafting surgery; however, the effects of surgery are known to persist for 6 months or more. Studies that have compared postoperative survival in women and men beyond hospital discharge report disparate results with regard to the independent effect of gender per se on ultimate survival.

Design: This investigation was a prospective, observational study.

Setting: The study was a multicenter investigation involving 24 US medical centers.

Participants: There were 2,048 patients undergoing isolated coronary artery bypass graft surgery enrolled between September 1991 and September 1993 and after discharge.

Interventions: There were no interventions with this prospective observational study.

Measurements and main results: Preoperative demographic variables, medical history, and angiographic data were collected for each patient at the time of enrollment. Patients' vital status through the National Death Index up to August 31, 1998, were added to assess postoperative long-term survival. For survivorship analysis, the Kaplan-Meier product-limit method was used with Cox regression model. Survivorship analyses were performed separately and in combination on mortality within 30 days and 6 months of coronary artery bypass graft surgery and during the entire postoperative follow-up period. Among women, preoperative disease status, as expected, was more severe than that in men. Women were older (p = 0.0001) and had more comorbidity, such as congestive heart failure (p = 0.0019), diabetes (p = 0.0001), anemia, and hypertension (p = 0.0001). After surgery, unadjusted survival of 6 months and 5 years in women was worse than that in men. However, there were no gender-related differences in short- or long-term survival after adjusting for covariates in the multivariate model. Preoperative conditions, such as congestive heart failure, anemia, diabetes, and advanced age, are indicative of greater risk in both women and men for lower survival after coronary artery bypass graft surgery.

Conclusions: Disease prevalence in women, and not gender per se, affects mid- and long-term survival after cardiac surgery. Attention, therefore, should be focused on efforts to reduce or modify such disease prevalence earlier in women, which may in turn allow longer survival after surgical intervention. Differences in postoperative survival between women and men were related to the gender differences in the distribution of preoperative risk factors.