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Do women fare worse than men following cardiac surgery?Reviewers: Mark A. Chaney, MD
Coronary artery disease is the leading cause of death for women in the United States, accounting for almost 250,000 deaths annually. Despite advances in cardiopulmonary bypass and postoperative care that appear to have reduced perioperative mortality in men, the perioperative mortality after coronary artery bypass grafting (CABG) in women remains twice that of men.1 The questions of whether and why women have higher probabilities of poor outcomes after CABG have been recently and repeatedly asked. Numerous studies have demonstrated an increased hospital mortality after CABG in women when compared to men. The Coronary Artery Surgery Study (CASS) Registry showed that women had an operative mortality of 5.3% compared with 2.5% for men.2 The Society of Thoracic Surgeons National Cardiac Surgery Database, which retrospectively examined 334,913 patients undergoing CABG surgery since 1994, showed that women had an operative mortality of 4.5% compared with 2.6% for men (P<0.0001). Although the mortality rate remained significantly higher for women when each of the multiple risk factors were examined univariately, multivariate analysis revealed that women continued to have higher mortality than equally matched men in low and medium risk spectrums. Only among very high-risk patients was there a sex-neutral mortality risk.3 The National Cardiovascular Network Database (1993-1999) also showed that women had higher hospital mortality rates than men, and women younger than age 50 years were three times more likely to die than their male counterparts. This database also showed that women had a greater occurrence of perioperative complications (most importantly, renal failure, neurologic complications, and acute myocardial infarction), and these complications were more marked at younger ages.1 In contrast, a report from the Bypass Angioplasty Revascularization Investigation (BARI) showed comparable unadjusted 5-year mortality rates for women and men.4 Koch and associates also suggested that in well-matched patients, female gender was not a risk factor for in-hospital mortality and had minimal impact on postoperative morbidity.5 In a study by Brandrup-Wagnsen and associates, the unadjusted mortality rate was significantly higher in women than men two years after CABG; once the researchers adjusted for baseline comorbid diseases, however, there was no sex-related difference in mortality at either two or five years.6 While the majority of studies seem to indicate that women are at increased risk, there is still much debate regarding whether the difference in mortality between men and women after CABG is due to female sex per se or to a higher prevalence of unfavorable risk factors in women by the time they present for cardiac surgery. Women appear to have more urgent or emergent presentations, tend to be older on presentation, and have multiple comorbidities (diabetes, hypertension, obesity, depression) when compared with men. Diabetic patients for CABG surgery have been shown to have longer intensive care and hospital stays, greater need for inotropic agents, hemotransfusion, and dialysis, and more frequent renal failure, stroke, mediastinitis, and wound infection.7 O'Connor and associates showed that greater than 97% of the excess mortality among women reflected those with diabetes or urgent or emergent presentation.8 The more frequent urgent and emergent presentation of women for CABG, as well as the fact that women with acute myocardial infarction are significantly less likely than men to have undergone cardiac catheterization before their myocardial infarction9, suggests that, in some cases, women with significant coronary artery disease may not be appropriately identified and referred for more invasive studies. Other recovery comorbid factors for women include an excessive decline in physical functional level and an increase in depressive symptoms.10 Certain technical factors, such as small coronary arteries in women, use of fewer grafts, and underuse of the internal mammary artery in women may also be associated with a greater incidence of postoperative angina and higher graft occlusion rates.3,8,11 Although numerous investigations have showed increased mortality in women after cardiac surgery, many questions remain unanswered. Is this increased operative mortality early perioperative mortality, or mortality, during the remainder of the hospital stay? Does perioperative control of risk factors, particularly diabetes, hypertension, and hyperlipidemia, exert an effect? Does early diagnosis and referral or change in surgical technique have any role in improving outcome in women? An excess of bleeding complications has been described for women with all interventional procedures. Does this play a role in mortality? What is the role of preoperative anemia in women? Are there pathophysiologic differences in coronary plaque and in coronary vasoactivity and/or endothelial function that may contribute to the adverse outcome? These, and multiple other questions from the available data, must be studied further to explain the perceived differences between men and women, to identify gender-specific risk factors, and to correct any disparities in treatment when found. References
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