Past SAVR Outcomes Matter More Than Volume in Determining Future Performance

SAN DIEGO, CA—Although surgical volume is associated with clinical outcomes, an institution’s prior outcomes are a better predictor of future results, according to new data presented at the annual Society of Thoracic Surgeons (STS) meeting.

Given the emergence of TAVR as alternative therapy for the repair of severe aortic stenosis, these findings should encourage cardiac surgeons to start policing themselves instead of waiting for outside regulation, experts say.

“In the era of the changing role of AVR and the management of aortic valve disease, there should be continued vigilance in improving valve surgery outcomes,” said lead researcher Vinod Thourani, MD (MedStar Heart and Vascular Institute, Washington, DC). “Low-volume sites with a known history of increased mortality and/or major morbidity, should really seek advice in quality improvements.”

The study, which was presented during a late-breaking clinical trials session, included 234,556 patients who underwent nonemergent SAVR and were enrolled in the STS registry between January 2013 and March 2018. Overall, 61.5% received isolated SAVR, while the rest also had CABG. More than one-third (36.5%) of cases took place at institutions with an annual cardiac surgery volume of more than 100 cases, and 25.9% and 7.0% were at centers with volumes of 26 to 50 and 25 or fewer cases, respectively.

In adjusted analyses, there were clear relationships between annual hospital case volume of isolated SAVR as well as SAVR plus CABG for both mortality and mortality/major morbidity (P < 0.001 for all). Other individual endpoints like stroke (for isolated SAVR only), renal failure, and need for reoperation were also associated with case volume.

Compared with centers performing more than 100 procedures annually, those that did less had higher risks of mortality following both isolated SAVR and SAVR plus CABG.

Mortality Risk By Hospital Case Volume (Compared With > 100 Cases)

In additional analyses comparing outcome and volumes between the periods of 2013-2015 and 2016-2018, the researchers found that for mortality alone an institution’s prior volume and outcomes explained their latter outcomes to a similar extent. However, “for the composite of mortality and morbidity, a far greater proportion of the variation was explained by an institution’s prior outcomes and significantly less so by the prior volume,” Thourani reported.

Future Regulation

To date, there has been no centralized way of monitoring SAVR volume and outcomes on a hospital basis, according to Thourani. “Nobody has done that,” he said. “I think the TAVR phenomenon has made us look at ourselves a lot more.”

The data from this study demonstrate that while “the majority of low-volume centers do great, there's probably 20% to 30% of centers that are really bringing everything down,” Thourani continued. “I think that looking at these data, how could you not set up a system where centers get reviewed and try to bring everybody to the same level? That’s the next initiative. This is the first time we've shown this data, but that’s part of the reason we're interested in looking at how to make those centers better.”

Session co-moderator Marc Moon, MD (Washington University School of Medicine in St. Louis, MO), said he believes that payers could establish an initiative aimed at quality improvement, but that it would be difficult for the STS to police.

“There's two different ways to look at it,” Thourani replied. “One is we could regulate ourselves, or we could allow somebody else regulate us. And I would prefer us regulate ourselves instead of having someone else from Washington, DC, who doesn't even know what an aortic valve looks like come into it. There’s some discussion we need to have on that.”

In a discussion following the presentation, Ralph Damiano, MD (Washington University School of Medicine in St. Louis), agreed. “It's important that we've got to start looking at it because if we don’t start looking at this, other people will.” He pointed out, however, that surgeons often practice at multiple hospitals, “so looking at institution volume is probably not very good and maybe why you're so scattered in your data.” He asked whether it’s possible some low-volume hospitals do well because high-volume surgeons practice there.

Possibly, Thourani answered, noting that he has worked simultaneously at multiple hospitals in the past and his personal outcomes did not vary by institution. “The original proposal for this study was to do volume and surgeons presented together. Once we started diving into this data, we realized that that is just too much for one abstract,” he explained. The next step in this research will be to look closer at surgeon volume, which “will get more controversial I believe.”

Surgeon volume will be the “critical differentiator” moving forward, Damiano said, because “it's very hard to maintain extraordinarily good results and low mortality in very-low-volume centers. I think this is an area where the societies have to step up. I think the government is eventually going to.”

Notably, audience member and past STS president Frederick Grover, MD (University of Colorado School of Medicine, Aurora), said the finding that not all low-volume centers are the same is “very important,” and this is why paying attention to outcomes is so critical. “There's been an overemphasis of people trying to weed [out] programs by strictly volume without looking at what their outcomes are,” he said.

As far as the role of societies, “it's tricky in the STS because there are lot of legal ramifications,” he said, noting, for example, that the organization would not want to “get caught in the middle” of the politics of comparing two groups within a private hospital. Overall, monitoring outcomes “is something we ought to do, and a lot of us feel that way, but a lot of it is how we do it,” Grover said. “We’d have to be invited by a hospital, and we'd have to really be sure that it's a bona fide thing and not an inside fight or something like that.”

“I agree,” Thourani said. “If we don’t do it, we’re hurting patients. At the end of the day, that's where the line in the sand should be drawn.”