OTTAWA, ON — When surgeons at the University of Ottawa Heart Institute embraced multiple arterial revascularization over the use of venous conduits more than 2 decades ago, it wasn’t clear whether women—well-known to have lower referral and CABG rates than men—would benefit equally.
A retrospective look at their experience from 1990 to 2015 shows a significant, stepwise increase in the use of multiarterial revascularization among both sexes, although women continue to receive less complete revascularization than men[1].
Among the 19,557 patients undergoing isolated CABG, bilateral internal thoracic artery (BITA) grafting was significantly more common in men (odds ratio 1.67, 95% CI 1.16–2.39).
The annual rate of increase in revascularization strategies was also higher over time among men than women for the use of BITA (1.59% vs 1.37%), three arteries (1.16% vs 0.73%), and any two arteries (2.34% vs 1.92%; for all P<0.001), according to the study, published recently in the Annals of Thoracic Surgery.
After propensity matching 627 male and female pairs for baseline differences in no less than 45 covariates, however, the researchers, led by Dr Habib Jabagi, found no differences between the sexes in the use of BITA, BITA in low-risk patients, or radial-artery use. Only the use of triple-arterial grafting was significantly greater among men than women (10.5% vs 7.3%; P=0.048).
“When patients were matched, it looked like they were getting about the same care. I think we’re doing a good job; this is a good story,” senior author Dr Fraser Rubens said.
As to why women aren’t undergoing more triple-arterial grafting, he replied, “I think it is this gender bias. A person will have a bias in the back of the head because of the last person they operated on who had a complication, and we do see women have a higher risk of complications because they’re smaller, it’s technically more difficult, and they come in with more diabetes, etc. So you can’t help but imagine that this is biasing our ability get these people the best possible operation.”
Dr Ellen Keeley (University of Virginia, Charlottesville), who was not involved in the study and served on the 2011 American College of Cardiology/American Heart Association CABG guideline committee, sounded a similar note.
“It seems that the matching resulted in no real differences between men and women from a demographic standpoint but still less use of three arterial grafts in women,” she said in an email. “The usual reason that is brought up regarding this topic is smaller arterial size in women; however, the authors accounted for this and found this is not the driving force.”
She continued, “I think this is an important paper because it underscores the fact that many of the preconceived notions regarding use of arterial grafts in women undergoing CABG are not supported by data. Hopefully, by highlighting this issue, surgical practice will change.”
Rubens observed that the rate of bilateral mammary revascularization at his institution is up to 45%, or 10-fold higher than that in the Society of Thoracic Surgery database in the US. It is not dissimilar, however, to the practice at many European institutions that have adopted the multiarterial approach and “ended up with pretty good results.”
“So I see a pretty dramatic potential for changing the practice pattern in North America,” he added. “It’s possible we’re doing too many, that we’re too aggressive, but maybe the sweet spot is somewhere between the two, and my hope is that research like this will introduce the possibility and feasibility for other institutions in the States that could be doing this and may be able to get better results.”
Commenting to theheart.org | Medscape Cardiology, Dr Ron Blankstein (Brigham and Women’s Hospital, Harvard Medical School, Boston) said he’s unaware of data showing clinical and survival advantages for triple-arterial grafting, as there may be for BITA, or that women have worse outcomes because of this disparity in utilization. Even for BITA, the evidence is uncertain, as the large randomized ART trial showed no difference in 5-year mortality or cardiovascular events but more sternal wound infections in patients receiving BITA vs a single mammary artery.
“I think it’s a success story for a single institution that they’re using more arterial revascularizations, but in the absence of data showing that this has led to significant improvement in outcomes, it’s hard to generalize these results to other practice settings,” he said. “At the end of the day, it shows that it’s feasible to use as many arterial revascularizations in women as in men, particularly when they’re similar in terms of their other risk factors.”
Rubens acknowledged that the benefit of using three arteries during CABG is unknown but said it will take years and massive registry studies or randomized controlled trials to determine.
“Whether there’s a benefit, I don’t know, but I certainly would want it if I was going to have an operation on my heart,” he said. “It makes every biological sense that it would be a better operation, and women aren’t getting it.”
Both men agreed that the early detection of coronary artery disease in women is a critical step. Blankstein observed that women may be less likely to have significant obstructive disease or stenosis, the type of disease cardiologists often look for with invasive angiograms. But on the other hand, it’s clear that noninvasive tests such as positron emission tomography, myocardial perfusion imaging, and measuring coronary flow reserve can identify women with diffuse disease and high enough risk that they may benefit from revascularization, and particularly bypass surgery.
“So I think that knowing how to better diagnose disease in women and also identify women that are more likely to benefit from bypass surgery are really important steps here,” Blankstein said.
Rubens and coauthors reported no study sponsorship or relevant financial relationships, nor did Keeley and Blankstein.
Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.
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