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Case volumes still matter in transcatheter aortic valve replacement (TAVR) outcomes, despite recent advances in technology and patient selection, a registry study showed.

Among centers participating in the Transcatheter Valve Therapy (TVT) Registry from 2015 to 2017, hospitals performing the most transfemoral TAVRs per year had 19.45% lower adjusted risk of 30-day patient mortality than those performing the fewest TAVRs (mean annualized volume 143 vs 27 procedures per year).

Analyzing hospital volume by quartiles produced similar results, as risk-adjusted mortality was 3.19% in the lowest volume quartile doing 36 or fewer per year and 2.66% in the highest quartile doing at least 86 per year (adjusted OR 1.21, 95% CI 1.03-1.41).

These findings reported by Sreekanth Vemulapalli, MD, of Duke University Medical Center in Durham, North Carolina, and colleagues in the updated similar results from the TVT Registry presented to a Centers for Medicare and Medicaid Services (CMS) advisory panel in mid-2018. In March, the agency proposed to ease but not eliminate these requirements.

"These results are from current practice in the United States and illustrate the major improvement in 30-day mortality with TAVR, from 7.5% in 2012 to a modeled rate that now approaches 2.5 to 3.0% in transfemoral TAVR," the investigators wrote.

However, that volume-mortality association persists "despite improved patient selection, technology, and techniques as well as expansion of indications to intermediate-risk patients," they added, noting that lower-volume hospitals also had greater variability in mortality.

"In general, I think these findings support the from CMS, which impose strict volume thresholds," commented Robert Yeh, MD, of Beth Israel Deaconess Medical Center in Boston.

"The CMS requirements go a bit farther than this though, including requiring maintenance of surgical AVR volume, which is supported by previous literature showing a relationship between surgical AVR outcomes and subsequent TAVR quality," he added.

Vemulapalli and colleagues analyzed 113,662 TAVR cases listed in the TVT Registry, of which 84.7% were performed through a transfemoral approach. In total, there were 555 hospitals and 2,960 operators involved.

The volume-outcomes relationship appeared to hold strong even after a center should have passed the learning curve for TAVR: A sensitivity analysis excluding the first 12 months of transfemoral TAVR at each hospital still showed greater odds of adjusted 30-day mortality among lowest-volume compared to highest-volume centers (3.10% vs 2.6%, adjusted OR 1.19, 95% CI 1.01-1.40).

Centers with lower procedural volumes were more likely to be rural, and they performed relatively more TAVRs on racial and ethnic minorities, the researchers noted.

TAVR's accessibility in the U.S. was one of the key considerations discussed by the CMS advisory panel considering its TAVR National Coverage Determination (NCD), which stipulates institutional and operator volume requirements for reimbursement.

"The question becomes whether the imposition of these volume thresholds by CMS will reduce access of this life-saving technology to historically disadvantaged populations and increase healthcare disparities. Making sure that we enable these populations to be able to receive TAVR will be an important priority as new regulations go into effect," Yeh told MedPage Today.

Vemulapalli's group cautioned against linking reimbursement to direct quality metrics without an external certification or accreditation system. "In addition, we think an updated NCD should include an effective mechanism to require hospitals to submit complete and accurate data for quality metrics to be valid," the investigators said.

They acknowledged that their retrospective observational study had potential for residual confounding. Furthermore, the TVT Registry only captured TAVR cases performed commercially and did not count those included in clinical trials.

“I think the volume/outcomes relationship they found makes sense,” commented Michael Reardon, MD, of Houston Methodist Hospital. “In general the more that you do of anything, the better you get at it.”

But he questioned whether volume is a marker for operator excellence or a marker for valve program excellence built through years of aortic valve replacement work.

This can depend on how each institution does things, suggested Reardon, who was not involved in the registry analysis. For instance, a center can achieve 100 TAVR cases a year with a single team that includes a cardiologist and a surgeon — or spread them out across four separate TAVR teams. Moreover, some “teams” don’t really have more than one main operator, as the other person is mainly on standby, he said.

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