Original Articles
Impact of gender on coronary bypass operative mortality

https://doi.org/10.1016/S0003-4975(98)00358-0Get rights and content

Abstract

Background. In spite of many reports investigating the influence of gender on coronary artery operations, it is still uncertain whether gender is an independent risk factor for operative mortality. A major problem of previous reports has centered around the fact that men and women constitute quite different populations, thereby making direct comparisons difficult.

Methods. The Society of Thoracic Surgeons National Cardiac Surgery Database was used to retrospectively examine 344,913 patients undergoing coronary artery bypass graft operations from 1994 through the most recent data harvest. The operative mortality of male and female patients was compared for a variety of single risk factors and combinations of risk factors. A logistic risk model was used to account for all important patient parameters so that individuals could be stratified into comparable categories allowing for direct comparisons of risk-matched male and female patients.

Results. The univariate analysis showed that the 97,153 women carried a significantly higher mortality for each of the risk factors examined. The multivariate analysis and the risk model stratification showed that women had significantly higher mortality as compared to equally matched men in the low- and medium-risk part of the spectrum, but in high-risk patients, there was no difference between male and female mortality.

Conclusions. Gender is an independent predictor of operative mortality except for patients in very high-risk categories.

Section snippets

Material and methods

The population was taken from patient records registered in the STS National Database from 1994 through the most recent data harvest in 1996. There are 344,913 patients registered as having isolated CABG operations in this period.

These patient records were extracted for analysis using standard statistical software (Statistical Analysis System [SAS] version 6.09 for Windows; SAS Institute, Cary, NC). All p values were determined using χ2 tests with the appropriate degrees of freedom. Specific

General demographics

There were 97,153 women (28.17%) and 247,760 men (71.83%) in the population. The OM for the entire population was 3.15% (10,853/334,913). For women the OM was 4.52% (4,388/97,153), whereas men had a 2.61% (6,465/247,760) mortality (p < 0.001).

A comparison of risk factors for men and women (Table 2) shows that there were significant differences in the two populations. In general, women were older, had a higher incidence of diabetes, hypertension, and peripheral vascular disease, and underwent

Comment

Women are generally considered to have a higher risk of OM after CABG operations. The most common explanations for this observation have centered around the fact that women have smaller, more technically challenging coronary vessels, the less frequent use of IMA grafting in women, and a referral bias causing women to present for surgical intervention at a more advanced stage of disease. On the other hand, some reports indicate that there is no real difference in CABG operative mortality between

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