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Operators continue to disagree on the necessity of conducting a randomized controlled trial of transcatheter aortic valve replacement (TAVR) in people with bicuspid anatomy, a prominent group that had been excluded from the landmark trials.

The interest in TAVR for this group comes at a time when operators already produce excellent outcomes with surgery. Although observational studies suggest bicuspid patients could share in the same early benefits as other TAVR recipients, these data are inherently limited by potential biases and short follow-up thus far, especially when it comes to younger, low-risk patients.

A randomized trial would at least overcome the issue of selection bias in registries and provide more information on the impact of aortopathy in the TAVR population, suggested Vinod Thourani, MD, of Piedmont Heart Institute in Atlanta.

"There are enormous gaps in knowledge regarding case selection," he said during a debate at the Transcatheter Cardiovascular Therapeutics (TCT) meeting, held in Orlando and broadcast online.

Moreover, as up to half of low-risk TAVR candidates have bicuspid anatomy, the durability of the device in these patients and the heterogeneous phenotypes within bicuspid anatomy remain important and unresolved issues, according to Lindsey Prescher, DO, of Walter Reed National Military Medical Center in Bethesda, Maryland.

On the other side of the debate, Prescher argued that a randomized trial is still not going resolve all the issues surrounding bicuspid TAVR unless it is inclusive of all-comers and consecutive recipients of both surgical and transcatheter aortic valves at each site.

That is just not feasible, she said.

What's more, to answer the question of bicuspid phenotype, a trial would have to consider at least 10 different anatomic variables, which would require enrolling 3,000 to 4,000 patients, said session co-moderator Thomas Modine, MD, PhD, of Centre Hospitalier Universitaire de Bordeaux in France. "My concern is the number of variables in how to design this study."

Thourani acknowledged that it is "unlikely" for a bicuspid trial to get funded and enrolled at this point, and operators already "have a good idea" of which patients will do well after TAVR.

Nevertheless, if he were to design such a study, it would enroll all-comers with bicuspid aortic stenosis at low or intermediate surgical risk. There would be one group with favorable anatomy randomized to TAVR versus surgery, and another group of high-risk patients with excessive calcification or other unfavorable anatomy getting TAVR and followed in a registry. The primary endpoint would be 2-year mortality and stroke, with follow-up at 5 years and again at 10 years.

There would also need to be a parallel registry of all bicuspid patients who had been turned down for TAVR for a detailed CT analysis, Thourani added.

Session panelist Alexandra Lansky, MD, of Yale School of Medicine in New Haven, Connecticut, said she favored a randomized trial that would establish which patients really benefit from TAVR. "What Vinod proposed was a very good approach," she said.

Prescher stressed that the successes to-date for TAVR in people with bicuspid anatomy cannot be extrapolated to all patients, given that experienced centers have a more nuanced understanding of anatomy and are more selective of their patients.

"Low-volume centers that participate in the majority of patient care are qualitatively different than the experienced centers that were participating trial centers," she said, adding that replicating this expertise is a challenge due to the growing number of TAVR centers with low volumes.

There are already at least 715 TAVR sites in the U.S., she said, citing an estimate from August 2020 (a more current estimate is 780).

Rather than a randomized trial, clinicians need longer-term registry data with data points on Sievers classification, calcium scoring, and valve durability. Additionally, the success of high-volume, experienced heart care teams needs to be reproduced in smaller centers, she urged.

Such caution will not always be matched by enthusiastic patients, however: If a 60-year-old with bicuspid anatomy came in intent on having TAVR but was also a good candidate for surgery, surgery would be the first choice for Rishi Puri, MD, PhD, of the Cleveland Clinic in Ohio, he said at the end of the TCT debate.

If the patient pushes back hard against surgery, the operator might give in, and TAVR valve choice then becomes important, Puri acknowledged.

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