CABG has been shown to improve survival in patients with multi-vessel coronary artery disease and left main coronary artery disease [7, 8]. The association of gender with mortality and morbidity after CABG has been debated by many studies for more than 20 years. The results of studies analyzing role of female gender as an independent risk factor for long-term survival after coronary artery bypass surgery has been variable and controversial (Table 7.1) [9–13]. In a report of 8,907 CABG patients, women were found to have lower long term survival in comparison to men, but patient related risk factors and not gender itself was found to be associated with poor outcomes [9]. In contrast, report from Bypass Angioplasty Revascularization Investigation (BARI) suggested that men and women had similar post-CABG survival at 5 years. However women had higher risk profile and after adjusting for multiple risk factors, female sex was an independent predictor of improved survival at 5 years [10]. Yet some other reports indicated the female gender was associated with decreased likelihood of survival long term. Weintraub et al. reported that 20-year survival after CABG was 37 % in men and 29 % in women [11].

Certain pre-operative risk factors have been found to be unique characteristics of either sex. A number of researchers have concluded that this difference in pre-existing risk factors may directly or indirectly influence short and long term outcomes. The European System for Cardiac Operative Risk Evaluation (Euro-SCORE) is a well-validated scoring system to help predict mortality from cardiac surgery based on certain risk factors [14]. In this risk stratification, female gender is an independent risk factor for worse outcomes after cardiac surgery.

In general, male CABG patients have lower left ventricular ejection fraction, significant smoking history and history of prior myocardial infarction [13, 15, 16]. Female CABG patients on the other hand, generally present at an older age compared to their male counterparts. This could be related to protective effects of female sex hormones in reproductive age group. Older age at presentation and its association with co-morbid conditions may contribute to increased surgical risk and poor outcomes in women. Women have higher incidence of peripheral vascular disease, hypertension, diabetes mellitus, chronic renal insufficiency and congestive heart failure [13, 15, 16]. Women are more likely than men to undergo emergent cardiac surgery and present with cardiogenic shock [17]. Emergent cardiac surgery in women may be a reflection of referral bias for women presenting at more advanced stage of coronary artery disease with associated hemodynamic instability which may negatively impact survival.

Female patients have generally smaller body mass index and body surface area (BSA) in comparison to their male counterparts. Most reports conclude that smaller BSA in female CABG patients is not a significant risk factor for operative mortality [15, 18]. A retrospective analysis by Rannuci and colleagues from Italy found that female gender and small body surface area were associated with severe intraoperative hemodilution and subsequent need of blood transfusions. They commented that larger BSA in women is likely related to obesity and hence associated with prolonged intensive care unit (ICU) length of stay. Men with small BSA were reported to have longer ICU stay likely resulting from hemodilution associated with smaller BSA and its associated complications [18]. Anemia is a well-identified predictor of poor outcomes in patients with coronary artery disease and in general population. Post-operative anemia after CABG surgery may persist for months and has been found to be associated with impaired outcomes. Westesbrink et al. reported that for every 1 mg/dL decrease in Hb, there was a 13 % increase in cardiovascular events and a 22 % increase in all-cause mortality in CABG patients [19]. Women tend to have more anemia pre and post-operatively and are more likely to receive blood transfusions which put them at further increased risk of complications and poor outcomes compared to men [19–21].

The use of internal mammary artery (IMA) for bypass grafting has been shown to be associated with improved short and long term survival in patients undergoing CABG. Despite this fact, many studies have reported significantly less use of IMA conduit in women [15, 22, 23]. Study of 541,368 coronary artery bypass graft surgery procedures reported by 745 hospitals in the STS National Cardiac Database from 2002 through 2005 revealed that IMAs were used less frequently in women than men (odds ratio for at least one IMA: 0.62; 95 % confidence interval: 0.61–0.63, odds ratio for bilateral IMA: 0.65; 95 % confidence interval: 0.63–0.68) [23]. Some authors relate this disparity to smaller BSA in women while others found that the difference persists even after the adjustment for BSA [24].

Off pump CABG in comparison to conventional CABG on cardiopulmonary bypass was thought to be associated with improved outcomes and less complications in post-operative period in terms of need of blood transfusion, neurological complications and major adverse cardiac events. However, two major clinical trials published recently (CORONARY: CABG Off or On pump Revascularization Study, and GOPCABE: German Off-Pump Coronary Artery Bypass Grafting in Elderly Patients) reported no significant difference between off pump and on pump CABG group in outcomes of death, myocardial infarction and stroke [25, 26]. However, there were reportedly fewer transfusion and more incomplete revascularization in off pump CABG group. In the pre-specified sub-group analysis of CORONARY trial, no significant interaction was found between operative techniques and gender for primary end-points [25].

Current data on gender and its influence on complication after CABG are variable. Women have been found to report more post-operative angina than men [10, 12], which may be related to underutilization of IMA conduits, less complete revascularization and smaller coronary size in women, and gender differences in pre-operative risk profile. However, women were found to less likely require percutaneous or surgical re-intervention [12]. Post- CABG neurological complications contribute to significant morbidity in this population; however data remains inconclusive about its association with gender. Some studies report significantly higher neurological morbidity in women [27, 28], others find no relationship with either sex [22], and yet there are also reports of worse neurological outcome in men [7]. Most studies have found no association of gender with post-operative risk of infections despite existing differences in baseline clinical characteristics [13, 22, 29]. Women tend to have longer hospital stay, ICU length of stay and more days on mechanical ventilation and more commonly require intra-aortic balloon counter-pulsation, vasopressors and dialysis [12, 22, 30].

In addition to reports on association of gender with CABG outcomes, there has been increased interest by many authors to understand its relationship to cardiac valvular surgeries and combined CABG and valve surgeries. Combined CABG and valve surgeries have increased mortality and morbidity than CABG alone or primary valve surgery alone. The role of gender as an independent risk factor for patients undergoing combined valve and CABG surgery remains unclear. Some authors report that female gender is associated with worse outcomes in terms of long term survival while others found no association [31, 32]. Women were reported to have more risk factors in comparison to men, which is similar to the findings of studies reporting influence of gender on CABG outcomes. The pre-operative risk factors should be strongly considered when analyzing outcomes after combined surgeries.

According to National Health and Nutrition Examinations Surveys 2007–2010 data, an estimated 5.1 million (2.1 %) Americans ≥20 years of age have heart failure. Of these 5.1 million heart failure population, 2.7 million are male and 2.4 million are females. It is projected that by 2030, the prevalence of heart failure will increase by 25 % of 2013 estimates [1, 39]. Although survival after diagnosis of heart failure has improved over time; such improvement is less evident in women and elderly as shown by data from the Olmsted County Study. Heart failure mortality remains high and nearly 50 % of heart failure population dies within 5 years of diagnosis [40]. According to the data published by National Hospital Discharge Survey; from 2000 to 2010, the rate of CHF hospitalization for males under age 65 increased significantly while the rate for females aged 65 and over decreased significantly [41].

The benefits of heart failure therapies have been supported by evidence derived from multiple large multicenter randomized trials. Heart transplantation remains the gold standard therapy and has been proven to improve survival in select patients with advanced end-stage heart failure. However, with limited availability of donor organs, longer waiting time or ineligibility of recipient due to number of reasons, this option might always not be considerable. In such situations, implantation of ventricular assist devices (VAD), as bridge to transplant, bridge to recovery or as a destination therapy, have been shown to improve survival and quality of life.