A dedicated, prospective randomised controlled trial (RCT) investigating the safety, efficacy and limitations of transcatheter aortic valve implantation (TAVI) versus surgical aortic valve replacement (SAVR) in different types of bicuspid aortic stenosis is “highly needed”, according to researchers writing in JACC: Cardiovascular Interventions.
The call comes in a viewpoint article, authored by Philippe Nuyens (Rigshospitalet, Copenhagen, Denmark) and colleagues, which aims to flag and address “important missing links in the current available evidence on TAVI in bicuspid aortic stenosis” as well as providing an initial impetus for the design of an RCT comparing the two approaches for the treatment of stenotic bicuspid valves.
Nuyens and colleagues write that the current available evidence on TAVI for the treatment of bicuspid aortic stenosis largely comes from observational or registry studies, which have mostly yielded reassuring results for TAVI—albeit based upon their inclusion of selected patients with favourable anatomy for transcatheter treatment.
“Another missing link,” they write, is that currently-available studies do not unravel which types or sizes of transcatheter valve are the better choices when treating specific bicuspid valves with TAVI. Additionally, they note that there is an absolute lack of long-term follow-up data as, among the currently available studies, there are nearly no reported outcomes beyond two years.
Despite this lack of data comparing TAVI and SAVR in bicuspid aortic valve patients, TAVI for the treatment of bicuspid aortic stenosis has received US Food and Drug Administration (FDA) approval.
“This approval may be somewhat premature and does not alter the fact that more prospective data are needed on the performance of TAVI versus SAVR in a non-selected, younger bicuspid aortic stenosis population,” Nuyens and colleagues write.
The paper goes on to present a study design proposal for a dedicated RCT comparing TAVI and SAVR in the bicuspid aortic stenosis patient population. “The goal of such a trial should be to provide insights on current aortic valve replacement practices in bicuspid aortic stenosis and to generate data and evidence that may influence guidelines and recommendations on the therapeutic choice for patients with bicuspid aortic stenosis and a longer life expectancy,” the paper’s authors state.
Long-term transcatheter valve durability will be a key question to answer in any potential bicuspid aortic stenosis trial, Nuyens et al detail, adding that this will necessitate the enrolment of young and low-risk patients to guarantee for a large enough population of alive and “at risk” patients at five years and beyond. The study population should also represent an all-comers, young population with bicuspid aortic stenosis, similar to that seen in daily clinical practice.
A non-inferiority trial design is likely to be the most logical choice, the researchers state, as TAVI is not yet a fully established therapy to treat patients with bicuspid aortic stenosis with longer life expectancy.
The primary endpoint could be a composite of death, stroke and valve-related hospitalisation at five years, estimated to have event rates of 20% and 23% in the TAVI and SAVR treatment arms, respectively, the authors suggest, anticipating that a total sample size of 940 patients is likely to be required to produce an adequately powered trial.