Women Still Face Higher Risks for Mortality After CABG

Women continue to have a higher risk of mortality and morbidity after coronary artery bypass grafting (CABG) compared with men, with no significant improvements seen over the last decade, a retrospective cohort study found.

Among over 1.2 million patients who underwent primary isolated CABG from 2011 to 2020, women had a higher unadjusted operative mortality versus men (2.8% vs 1.7%, P<0.001), as well as a higher overall unadjusted incidence of the composite of operative mortality and morbidity (22.9% vs 16.7%, P<0.001), reported Mario Gaudino, MD, PhD, MSCE, of Weill Cornell Medicine in New York City, and colleagues.

The attributable risk of female sex for operative mortality was 1.28 in 2011 and 1.41 in 2020, with no significant change over the study period (P for trend=0.38), while the attributable risk for the composite of operative mortality and morbidity was 1.08 in both 2011 and 2020, again with no significant change (P for trend=0.71), they noted in JAMA Surgery.

"I hope this paper is a wake-up call, and I hope that the take-home message for the surgeon is, 'we're not as good as we thought we were, and we need to do a better job in treating women undergoing cardiothoracic surgery,'" Gaudino told MedPage Today.

The disparities in CABG outcomes didn't change when comparing off- or on-pump CABG, or single-arterial versus multi-arterial CABG, the authors noted.

It is well-documented that women undergoing CABG have higher mortality and morbidity: women are referred to surgery later than men, with more cardiovascular risk factors than men, and "present more frequently with heart failure or in nonelective settings, such as cardiogenic shock or acute myocardial infarction," Gaudino and team wrote.

However, overall CABG outcomes have improved over time, even in increasingly high-risk patients. "As a community, we were hoping that with a general improvement in outcomes, the problem [seen in women] would have gone away, but it didn't," Gaudino said.

"Equitable delivery of the CABG procedure itself is paramount to improve outcomes for women," who are "less likely to receive a left internal thoracic artery graft to the left anterior descending coronary artery, considered the gold standard in CABG surgery," the authors wrote.

In an invited commentary, Brittany A. Zwischenberger, MD, MHSc, of Duke University Medical Center in Durham, North Carolina, and Jennifer S. Lawton, MD, of Johns Hopkins University in Baltimore, noted that "the study by Gaudino et al. should be regarded as an exploding flare in the sky for all clinicians who care for women."

"Reasons for the differences in outcomes are undoubtedly multifactorial and include every phase of care from the assessment of risk, the presentation, the diagnosis, and the perioperative treatment to compliance with postoperative rehabilitation programs," they wrote. "Similarly, the steps needed to address these differences should be multifactorial. Women must be treated with guideline-directed optimal medical and surgical care."

"It is imperative that both sexes must be evaluated in basic science research and women must be enrolled in clinical trials," they added. "Additionally, surgeon specialization in coronary surgery and the establishment of center specialization for women should be considered."

Gaudino and colleagues also pointed out that women have different anatomical and clinical characteristics than men. For example, smaller coronary arteries and CABG conduits in women can make CABG more technically complex and, thus, more likely to fail. Coronary arteries can also spasm more in women, which can be mistaken for coronary artery disease and lead to unnecessary surgery.

Furthermore, the amount of fluid inside cardiopulmonary bypass machines during surgery can cause complications with blood dilution and anemia related to differences in sex, Gaudino said.

Standardized protocols for coronary revascularization are informed by data taken from studies that predominantly included men, he and his co-authors explained. But rather than the oft-repeated mantra to simply include more women in clinical trials, Gaudino said, entire studies should be dedicated to investigating interventions for women only. He said that he is currently working on a clinical trial that is comparing clinical outcomes with single- versus multi-arterial grafts in women.

"Insanity is doing the same thing over and over and expecting a different result," said Gaudino. "We need to accept that what we have been doing so far is not working."

He and his team called for more studies directly comparing outcomes for CABG and percutaneous coronary intervention, for which a sex disparity also persists.

For this study, the authors used data from hospitals in the Adult Cardiac Surgery Database of the Society of Thoracic Surgeons, which accounts for 95% of the groups that perform cardiac surgeries in the U.S. They included 1,297,204 patients who underwent primary isolated CABG from 2011 to 2020, 24.5% of whom were women.

Female patients were, on average, older (67 vs 65 years), and had a higher incidence of hypertension, diabetes, chronic lung disease, cerebrovascular disease, and peripheral vascular disease compared with male patients. Women were also more likely than men to be symptomatic, to undergo urgent CABG, and to have single- or double-vessel coronary disease.

Gaudino and team noted that the database was limited in its level of detail, which meant that unmeasured variables could have played a role in sex-related outcomes. There was also the possibility of reporting bias or database errors, and the COVID-19 pandemic could have affected surgical outcomes in 2020, they said.

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