Surgeons More Likely to Stray From CABG Best Practices in Female Patients

Women are less likely than men to receive “guideline-concordant” CABG in the United States, according to newly released numbers from a Society of Thoracic Surgeons (STS) registry.

The study looked at three metrics to gauge quality: use of the left internal mammary artery (LIMA) to bypass the left anterior descending (LAD) artery, pursuit of complete revascularization, and multiarterial grafting. All are associated with better long-term outcomes, yet were employed by surgeons less frequently in female patients.

In a press briefing ahead of the virtual STS 2021 meeting, Oliver K. Jawitz, MD (Duke University, Durham, NC), the study’s first author, posed a question: “Why has there been a clear and persistent disparity in outcomes between male and female patients with coronary artery disease?”

Women are known to present later, be more likely to have atypical symptoms, suffer delays in diagnosis and intervention, and be less likely to receive guideline-directed medical therapy and referral for CABG, he said.

This is a call to action. Brittany A. Zwischenberger

These differences aren’t without consequence. Even the women who do undergo CABG face higher short-term mortality as well as morbidity, stressed senior author Brittany A. Zwischenberger, MD (Duke University), when presenting her abstract last weekend at STS 2021. Specifically, female patients are more likely than men to see increases in infection, readmission, poor functional status, lower participation in cardiac rehab, and less symptom relief after their surgeries.

“What,” she asked, “is happening here with CABG? Are we the surgeons doing anything different for men versus women [during surgery]?”

Their data set of more than 1 million people, Zwischenberger said, confirms on a larger scale what has previously been seen by smaller studies: that there are disparities even after adjustment for confounders. “This a call to action, an opportunity for [cardiothoracic] surgeons to modify CABG techniques to potentially improve CABG outcomes and survival in women,” she stressed.

Joanna Chikwe, MD (Smidt Heart Institute at Cedars-Sinai, Los Angeles, CA), commenting for TCTMD, said the study is “a classic example of high-quality research that’s nailed a problem that’s been staring us in the face for years, but [one] we haven’t taken the time to look at in depth. The surprising thing is really the extent to which women are underserved by cardiac surgery right now.”

Decade’s Worth of CABG Data

Zwischenberger, Jawitz, and colleagues included 1.2 million patients (median age 66 years; 25% women) undergoing first-time, isolated CABG between 2011 and 2019 who were tracked by the STS Adult Cardiac Surgery Database.

Using multivariable logistic regression, they adjusted for body mass index, body surface area, comorbidities, hospital region, and annual CABG volume by center, looking for potential interactions related to age, race, body size, ejection fraction, dialysis, hematocrit level, recent steroids, and home oxygen use.

Compared with men, women tended to be older (median 67 vs 65 years), had smaller body surface area (median 1.8 vs 2.1 m²), and more frequently had diabetes (55.4% vs 45.5%), congestive heart failure (20.0% vs 16.8%), peripheral vascular disease (16.1% vs 13.4%), and cerebrovascular disease (23.6% vs 17.3%). They were less likely than men to be Caucasian (75.6% vs 80.9%) and more likely to be Black (11.8% vs 6.2%).

The surprising thing is really the extent to which women are underserved by cardiac surgery right now. Joanna Chikwe

Female patients were less apt to receive LIMA-to-LAD bypass (adjusted OR 0.79; 95% CI 0.75-0.83). The cited reasons for this decision varied by sex. For women more often than men, the deterrents to guideline-based care were emergent/salvage procedure, previous mediastinal radiation, subclavian stenosis, and inadequate size or flow. Previous cardiothoracic surgery, on the other hand, was a more frequent deterrent for men.

Complete revascularization also was less common in female compared with male patients (adjusted OR 0.86; 95% CI 0.83-0.90), as was multiarterial grafting (adjusted OR 0.78; 95% CI 0.75-0.81).

After controlling for various interactions, female sex still independently predicted less adherence to the three guideline recommendations.

Future research, Zwischenberger told STS attendees, should attempt to understand the mechanisms driving the differences, search for any causal links to outcomes, and inform strategies aimed at eliminating disparities in care.

What is unexplained is why we have failed to apply the same surgical strategies in women that have proven to produce better surgical results in men. Robbin G. Cohen

Discussant Ourania Preventza, MD (Baylor College of Medicine, Dallas, TX), asked Zwischenberger how the STS as a professional society should apply this knowledge, and with which quality benchmarks.

“The authors have thought a lot about this, and we’ve identified several opportunities for new directions,” she replied.

STS registry participants already receive reports on surgical technique, which could be expanded to include sex-related details, so that hospitals can address areas in need of improvement, Zwischenberger suggested. Specific to LIMA use in CABG, the STS considers this a performance measure, one that also informs the National Quality Forum’s star ratings, and this could also encourage hospitals to track patient sex, she continued. Finally, the STS can work to educate surgeons on how to overcome disparities.

Striving for Change

Robbin G. Cohen, MD (University of Southern California, Los Angeles), speaking to the media, said “what is unexplained is why we have failed to apply the same surgical strategies in women that have proven to produce better surgical results in men.

“My guess is that the explanations are both technical and systemic,” Cohen suggested. “The surgical details of applying these [three] techniques in women who have smaller vessels and more-diffuse coronary artery disease may, quite frankly, take some surgeons out of their comfort zones. With improved training, enhanced experience, and greater awareness, this can be overcome.”

Asked by TCTMD if there are any valid reasons why surgeons depart from guidelines in women, Chikwe noted that surgeons treating women may be motivated by short-term concerns like wound healing—which tends to be slower in women, whose breast tissue has less blood supply—and length of surgery time, perhaps at the expense of long-term outcomes.

“Whether the patient is alive at 30 days is clearly of prime importance. However, it’s also incredibly important whether that patient’s alive at 1 year, 5 years, and 10 years and feels well [with] normal quality of life,” stressed Chikwe.

Strong evidence will drive practice changes, she predicted, mentioning the randomized ROMA trial, as will quality metrics that take the long view of patients’ trajectories over time.

This all occurs on the backdrop of the fact that, as in other areas of medicine, most of the studies that inform CABG technique were conducted in men. Furthermore, Chikwe added, only around 6% of today’s cardiac surgeons are women. “There is a huge amount of data outside our specialty that speak to the fact that if you don’t have a group of care providers that better reflects the population [receiving] care, then outcomes can be worse,” she said.

Correction: The initial version of this story incorrectly spelled Oliver K. Jawitz's last name as Javitz.