TAVR Outcomes Dependent on SAVR Hospital Volumes

SAN DIEGO, CA—Hospital volumes of surgical aortic valve replacement independently predict the same institution’s midterm TAVR outcomes, according to a new study presented this week. Additionally, SAVR case load seems to be inversely linked to the prevalence of adverse TAVR outcomes at both 30 days and 1 year.

“Our findings not only shed light on the lingering question of the influence of SAVR volumes on TAVR outcomes, but also emphasize the importance of sustaining a viable SAVR program within the heart team to achieve and improve TAVR outcomes,” presenter Sameer Hirji, MD (Brigham and Women’s Hospital, Boston, MA), said during the opening session of the annual meeting of the Society of Thoracic Surgeons, where he presented the results.

One thing that we can say for sure is that the higher-surgical-volume centers definitely do better. That is a fact. Tsuyoshi Kaneko

The analysis is based on Medicare data from 65,757 SAVR and 42,967 TAVR procedures performed between 2012 and 2015. On the low end, 3% of TAVRs were performed at hospitals that logged fewer than 50 SAVRs per year, while 19% of TAVRs were done at hospitals with annual surgical volumes of at least 300 cases.

Thirty-day and 1-year mortality following TAVR decreased as SAVR volume increased, but there was no similar trend observed for readmission rates.

TAVR Outcomes by Hospital SAVR Volume

Acute kidney injury, need for red blood cell transfusion, permanent pacemaker implantation, and major bleeding all increased following TAVR with decreasing SAVR volumes. Intensive care unit stay and median hospital length of stay were also reduced with higher SAVR volumes (P for trend < 0.001 for all).
Compared with the highest-volume SAVR centers after adjustment, those with 10 to 99 cases (adjusted OR 1.32; 95% CI 1.18-1.47) and 100 to 199 cases (adjusted OR 1.25; 95% CI 1.12-1.39) had higher post-TAVR mortality risks at 30 days; mortality risk was not higher at centers with 200 to 299 cases (adjusted OR 1.08; 95% CI 0.92-1.25). These relationships were confirmed by sensitivity analyses looking at transfemoral cases only, as well as at centers with above and below 50 SAVR cases.

‘The Million-Dollar Question’

To TCTMD, senior investigator Tsuyoshi Kaneko, MD (Brigham and Women’s Hospital), said he didn't think that the data “was going to be this clean—this much of a co-relationship between the outcomes based on the volumes and the centers. So, we were actually quite surprised when we saw this.”

But the reasons for why this might be remain unknown. “That's the million-dollar question,” Kaneko said. “We would like to think that the surgeon involvement and the surgeon expertise that they bring to the heart team has resulted in this excellent outcome, but there's also criticism that high-volume SAVR centers tend to be high-volume TAVR centers. Could that have caused the improved outcomes? I think that's the question that's not answered unfortunately by this paper. But one thing that we can say for sure is that the higher-surgical-volume centers definitely do better. That is a fact.”

Discussing the study during the session, Joseph Bavaria, MD (Penn Medicine, Philadelphia, PA), said the study findings “are incredibly timely as there is an intense debate on this subject culminating in a series of national policy actions governing the performance of TAVR in the United States of America.”

The Centers for Medicare & Medicaid Services convened a Medicare Evidence Development and Coverage Advisory Committee meeting last year to discuss the issue of appropriate TAVR volumes as part of its upcoming national coverage determination, but a consensus was not reached.

“The fundamental result from this analysis is that increasing surgical AVR volume is independently associated with improved TAVR results,” he emphasized.

Consequences of Minimums

Addressing the panel during the session, Thoralf Sundt, MD (Massachusetts General Hospital, Boston), who was not involved in the study, said that if the aim is to provide the best care for patients, then physicians shouldn’t resist TAVR, but rather embrace it as a complementary technology to surgery. Moreover, “surgical aortic valve replacement is still a great operation and we shouldn’t abandon the field,” he said.

However, Sundt brought up a common criticism of minimum required SAVR volumes—that some patients might be inappropriately diverted to SAVR to meet quotas—and asked how that should play into decisions in this field.

While this study was not designed to determine optimal TAVR volume cutoff levels, Hirji told TCTMD these may change over time anyway as TAVR is better understood. “What's essential is that you also need minimum SAVR volume requirements to assess the accountability, the long-term effectiveness of these projects, and also monitor outcomes of these younger programs,” he said. “Statistically, it is difficult to measure changes when you have very small thresholds, and that's one other argument to have certain minimum requirements, so we can keep track of these outcomes through societies such as the STS, the TVT registry, and make that mandatory as well so we can at least be objective in understanding what the outcomes are.”

Adding on, Kaneko noted that the implementation of minimum volumes would likely affect smaller private practice centers more so than larger academic hospitals. “[Smaller centers] are the hospitals that have a possibility to be in danger for meeting requirements, and they [might] tweak it in order to meet that requirement so they can do the procedures,” he suggested. “I do believe that is a concern. I think that's where we really have to think about these minimal requirements.”

Ultimately, “our message is not to say that surgeons should be the main player or should be the person that will be doing the TAVRs,” Kaneko stressed. “We're still a collaborative heart team and the concept of a heart team is very important, and that's what we want to accomplish. I think this concept has infiltrated on a society level, but I think in some aspects there's some drift and loss of interest because it's been used so frequently. But I think this paper will refuel that discussion of the importance of the heart team.”