Significant improvement in short-term mortality in women undergoing coronary artery bypass surgery (1991 to 2004)

This study sought to evaluate gender differences and trends in 30-day mortality after coronary artery bypass surgery (CABG).

Evidence for gender differences in short-term mortality after CABG is conflicting. Many studies were from single centers, included highly selected populations, or had limited clinical information for adequate covariate adjustment. We undertook a population-based analysis using detailed clinical data on all adults undergoing CABG in the province of British Columbia, Canada.

The study population comprised all residents 20 years and older who underwent isolated CABG between 1991 and 2004. Multiple logistic regression was used to examine the association between gender and 30-day mortality; time trend analysis was conducted by Mantel-Haenszel chi-square test.

The study cohort comprised 20,229 men and 4,983 women. Women were older and had more comorbid conditions than men, but had better ejection fractions and less extensive coronary disease. Thirty-day mortality decreased significantly in men (2.4% to 1.9%) and women (5.6% to 1.9%) over the 14-year study period. Overall, 30-day mortality was significantly higher in women (3.6% vs. 2.0%, p < 0.001), and adjustment for baseline differences did not remove this difference (odds ratio 1.42, 95% confidence interval 1.15 to 1.75). Adjustment for body surface area, an intrinsic gender difference, further attenuated the relationship (odds ratio 1.26, 95% confidence interval 0.96 to 1.64).

The 30-day mortality after CABG decreased significantly between 1991 and 2004, especially in women, suggesting that the gender difference in short-term outcomes is diminishing. The overall 42% higher mortality risk in women seems to be partially mediated through body surface area, a surrogate for vessel size.