Female gender does not increase perioperative risk in coronary bypass surgery

INTRODUCTION: Female gender has been identified as an independent risk factor for perioperative mortality in several risk scores for cardiac surgery. Since no explanation has been given for this, this study aimed to evaluate potential differences in the distribution of other risk factors between the genders.

PATIENTS AND METHODS: 10 714 consecutive coronary bypass patients were analyzed retrospectively. The distribution of the risk factors as used in the EuroSCORE was evaluated. Diabetes mellitus was added to the analysis as an additional risk factor. Patients aged between 60 and 70 years without any additional risk factors were directly compared in a subgroup analysis. Statistical analysis was done using the T-test or chi-square test where appropriate.

RESULTS: Female patients were significantly older compared to male ones (69.1 ± 8.5 vs. 65.4 ± 4 years, P < 0.05). The distribution of the analyzed risk factors did not differ except for diabetes mellitus: female patients were more likely to present with diabetes (42 % vs. 29 %, P < 0.05) and in diabetic patients, the incidence of insulin dependency was higher in female patients (50 % vs. 33 %, P < 0.05). Overall perioperative mortality was higher in female patients (2.7 % vs. 1.8 %, P < 0.05). This difference increased when diabetes was present (3.9 % vs. 1.8 %, P < 0.05) and was even higher in insulin-dependent patients (4.9 % vs. 1.9 %, P < 0.05). However, when adjusting for age and diabetes, the differences were reduced. This was most evident when subgroups of age-adjusted patients without any additional risk factors were analyzed: no gender-specific difference in perioperative mortality was observed.

CONCLUSIONS: Female gender itself did not present as an independent risk factor. The presence of diabetes mellitus increased the risk in female patients significantly more than in male patients. The higher prevalence of diabetes in female patients in combination with the older age at presentation might result in the higher overall mortality observed in female patients compared to men.