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The learning curve for balloon-expandable Sapien transcatheter aortic valve replacement (TAVR) worked out to about 200 cases in an analysis of the TVT Registry.

The more experience with these valves, the better the outcomes for the patient, as demonstrated by a relationship between case volume and 30-day mortality and stroke, with both associations persisting despite adjustment for patient risk and site random effects (P<0.0001 and P=0.009, respectively):

• Quartile 1 (first 38 cases): mortality 5.9% and stroke 2.7%
• Quartile 2 (cases 39-87): mortality 4.8% and stroke 2.2%
• Quartile 3 (cases 88-170): mortality 3.8% and stroke 2.2%
• Quartile 4 (cases 170 and over): mortality 2.9% and stroke 2.0%

After case number 201, centers made no more improvements in combined 30-day mortality or stroke, suggesting that the volume-outcomes relationship no longer held up, Mark Russo, MD, of Robert Wood Johnson University Hospital in New Brunswick, New Jersey, and colleagues reported in the Feb. 5 issue of the .

Looking only at experience with Sapien 3 implants, they found no learning curve or volume-outcomes relationship. Their conclusion was that with this current-generation device, "centers should expect to achieve consistently excellent outcomes even during early case experience."

The Sapien 3 was designed for easier positioning than its predecessors and has been linked to less paravalvular leak that is more than mild.

"These findings support that good outcomes are not merely a function of quantity, but are influenced by a constellation of factors, including technological advancements, best practices, collaborative knowledge programs, and organizational culture," according to Russo and colleagues.

The study is the latest to probe the importance of TAVR volumes ahead of a new National Coverage Determination expected from the Centers for Medicare and Medicaid Services this year.

One group previously tied increasing TAVR experience to better outcomes, whereas another suggested that the best TAVR outcomes came from centers maintaining high surgical and transcatheter case volumes.

As mortality in TAVR becomes ever rarer, it would be better to judge quality by composite outcome metrics that include clinical events as well as real measures of procedural quality, argued Saif Anwaruddin, MD, and Matthew Saybolt, MD, both of Philadelphia's Hospital of the University of Pennsylvania.

In addition, efforts may be better spent on "identifying areas for improvement, implementing best practices, and reinforcing organizational structure within lower performing sites," they wrote in an accompanying editorial.

The new findings do not support either adding more or shuttering existing low-volume TAVR programs, but "lead us to question the presence of [a] learning and a VOR [volume-outcomes relationship], at least with respect to latest-generation balloon-expandable valves and low-volume centers," according to Anwaruddin and Saybolt.

"However, like most things in our world, the truth is somewhere in the middle, and it would seem unlikely that a VOR is completely absent even for latest-generation TAVR," they concluded. "What remains apparent is that work needs to be done to better assess and to improve upon quality and outcomes in TAVR across all sites in the best interest of our patients."

Russo and colleagues limited their analysis to balloon-expandable valve implants (Sapien, Sapien XT, and Sapien 3) recorded in the TVT Registry from 2011 to 2017 (n=61,949).

With more experience, centers performed TAVR in younger, lower-risk patients. They also used more transfemoral access with more Sapien 3 valves.

Among the sites that performed their first TAVRs with the Sapien 3 (having no documented Sapien or Sapien XT cases beforehand), there was no association between implant frequency and 30-day mortality -- but a trend toward more major vascular complications with two or fewer device implants per month (P=0.052).

"The strong emphasis on the multidisciplinary heart team approach and group learning may explain why learning and VORs for TAVR differ from other cardiac interventions. For example, percutaneous coronary intervention, where a stronger VOR exists even after many generations of device technology, is most commonly performed solo and outside of a structured heart team," the authors wrote.

Nevertheless, they cautioned about the observational and self-reported nature of the data used.