Heart surgery endangers women in low-risk groups
A new study from the National Cardiac Surgery Database of the Chicago-based Society of Thoracic Surgeons yielded a stunning answer while raising other questions about women's outcomes following coronary artery bypass graft (CABG) surgeries.1 For low- to medium-risk patients, women had nearly twice the mortality rate of men. For high-risk patients, there was no difference in the mortality rate. The researchers conclude that gender is an independent predictor of mortality in all but high-risk patients.
Due to the paucity of good data on female cardiac surgery patients, the investigators retrospectively examined the 1994 through 1997 records of 344,913 CABG operations. Of those, 97,153 were women's. Both men and women were stratified into comparable categories allowing for comparisons of risk-matched males and females.
Those risk factor comparisons show these significant gender differences among CABG patients:
· Women - older, higher incidence of diabetes, hypertension, peripheral vascular disease, underwent nonelective procedures more often.
· Men - poor ventricular function, significant smoking history, need for re-operation.
The operative mortality for the entire study population was 3.15%. Breaking that down, 2.61% of the men died, and 4.52% of the women died. One explanation for the different death rates, theorize the researchers, is the dissimilar risk profiles of the male and female populations, making direct comparisons difficult.
Nonetheless, they conclude, "The present study indicates that gender is indeed an independent risk factor except for very high-risk patients." On the high-risk end of the spectrum it appears that other risk factors dominate patient outcomes overshadowing any gender-based differences. They add, "For low-risk and medium-risk patients, women carry a significantly higher risk of CABG operative mortality as compared with equally matched male patients." Why? Therein lies the mystery.
(Editor's note: To access the article on-line, free of charge, visit the Society of Thoracic Surgeons' Web site: http://www.sts.org.)
1. Edwards FH, Carey JS, Grover FL, et al. Impact of gender on coronary bypass operative mortality. Ann Thorac Surg 1998; 66:125-131.