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New data offer greater perspective on the long-term performance of transcatheter aortic valve implantation (TAVI) devices, but more insight into longer-term follow-up is still needed before interventionalists can gain the full picture of the optimal treatment for patients with aortic stenosis. This is among the messages of Nicolas van Mieghem (Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands), speaking to Cardiovascular News about the latest research shaping understanding on long-term TAVI outcomes.
“We now have randomised controlled trials comparing TAVI with surgery across the entire risk spectrum,” Van Mieghem comments. “With the the Evolut Low Risk and PARTNER 3 trials, the durability issue becomes more and more relevant, because the patient age is creeping down from 80 or more, to now 75 years or less, meaning that on top of the lower risk profile of the patients, their life expectancy exceeds 10 or 15 years,” he says, detailing why valve durability is now an issue of particular focus.
Ongoing research continues to add to the TAVI knowledge base, and two recent data releases are seen as providing important insights to the field both in terms of valve durability and of the benefits of the treatment in patients at low surgical risk.
At the 2023 Cardiovascular Research Technologies (CRT) conference (25–28 February, Washington DC, USA) Steven Yakubov (Riverside Methodist Hospital, Columbus, USA) presented analysis of five-year data on bioprosthetic valve dysfunction for Medtronic’s CoreValve™ and later-generation Evolut™ TAVI platforms from the CoreValve US High Risk and SURTAVI randomised trials.
Taking in data from 1,128 TAVI patients and 971 surgery patients, the pooled analysis evaluated valve performance and durability of the surgical transcatheter valves, assessed by the incidence of overall bioprosthetic valve dysfunction, including structural valve deterioration, non-structural valve dysfunction, thrombosis and endocarditis.
In the study, the CoreValve, Evolut R and Evolut PRO (Medtronic) transcatheter valves exhibited a significantly lower rate of bioprosthetic valve dysfunction compared to surgery (7.8% vs. 14.2%, p<0.001), and five-year rates of structural valve deterioration and non-structural valve dysfunction were significantly lower after TAVI compared to surgery (2.2% vs. 4.4%, p 0.004), and non-structural valve dysfunction (4.3% vs. surgical aortic valve replacement [SAVR] 8.8%, p<0.001).
“That is an important insight in the discussion on durability, and I think we are coming to a point where you can no longer make a claim that the surgical valve is the standard reference,” says Van Mieghem of these data. “There is no difference in the low rates of endocarditis and valve thrombosis, but there is clearly more structural and non-structural valve degeneration after surgery.”
According to Yakubov’s analysis, patients in both groups who developed bioprosthetic valve dysfunction through five years had around a 1.5-fold greater risk of death or hospitalisation for valve-related disease or heart failure than patients who did not develop bioprosthetic valve dysfunction.
Coming shortly after the presentation of the results of the analysis from the CoreValve US High Risk and SURTAVI trials, were three-year data from the Evolut Low Risk trial shared at the 2023 American College of Cardiology (ACC) annual scientific session (4–6 March, New Orleans, USA) by John Forrest (Yale School of Medicine, New Haven, USA) and published simultaneously in the Journal of the American College of Cardiology (JACC).
The Evolut Low Risk trial is a randomised, non-inferiority study, comparing TAVI with a self-expanding supra-annular bioprosthetic valve (CoreValve, Evolut R, or Evolut Pro) with SAVR in patients with severe aortic stenosis at low surgical risk.
The analysis presented by Forrest at ACC 2023 included 1,468 patients with a median age of 74 years. All of the patients enrolled in the trial had severe symptomatic aortic stenosis and were deemed to be at low risk from surgery, defined as having no more than a predicted 3% risk of death within 30 days of the procedure. Patients were randomly assigned to receive either TAVI or SAVR.
The results detailed by Forrest showed that 7.4% of those treated with TAVI had died or experienced a disabling stroke, compared with 10.4% of those treated with SAVR, a difference that fell just short of statistical significance (log-rank p=0.051). Occurrence of the secondary combined endpoint of all-cause mortality, disabling stroke, or aortic valve rehospitalisation was significantly lower in the TAVI group (13.2%) than in the SAVR group (16.8%, p=0.050). The results did show that mild paravalvular regurgitation was more frequent in the TAVI group (20.3% vs. 2.5%), but at three years there was no significant difference in the presence of moderate or greater paravalvular regurgitation (0.9% TAVI vs. 0.2% surgery).
In presenting the results at ACC, Forrest commented that the consistent benefit of TAVI at three years is not something that has been observed in prior studies, “and provides further evidence that TAVI deserves to be the dominant treatment modality for patients with aortic stenosis undergoing valve replacement.”
Van Mieghem comments: “What was relevant in that study was that TAVI with an Evolut system outperformed surgical valve replacement in terms of the composite endpoint of mortality and disabling stroke out to three years.”
“That is impressive because some people were alluding to a separation of the curves in terms of clinical outcomes in favour of surgery, and that definitely is not present in Evolut Low Risk, which is reassuring.
“There were more patients with mild paravalvular leak (PVL) or who required a pacemaker in the TAVI arm, but that did not affect the outcome at three years because still there was a strong trend in favour of TAVI in low-risk patients. That was an important observation,” he adds.
Though these data offer some reassurance over the durability of currently available TAVI platforms, one important discussion point for Van Mieghem is that there appears to be no class effect when it comes to valve durability according to the randomised trial data, meaning that not every transcatheter valve will behave in the same way. “Five-year data of intermediate-risk randomised controlled trials clearly suggest that self-expanding, supra-annular functioning devices behave differently than the balloon-expandable devices and also in comparison to surgery,” Van Mieghem says. And, while he comments that there is a “clear difference” in the behaviour of supra-annular valves relative to balloon-expandable platforms, datasets up to 10 years—as is planned through the Evolut Low Risk trial—will be needed before the claim can be made conclusively.
When considering the use of a supra-annular valve, Van Mieghem cautions that it is important to be mindful of facilitating future coronary access. “It is important to evaluate the coronary height, the width of the sinuses of Valsalva, and the ascending aorta to determine what the risk is for immediate coronary obstruction,” he advises. “In that regard, commissural alignment becomes very important, and the more extensive the coronary artery disease, the higher the likelihood for a future need for coronary interventions,” he adds, noting that this may influence device selection.
Looking to the future of TAVI trials, Van Mieghem says the question of durability will continue to be an important topic for research, particularly as the treatment is made available to younger patients.
“If we have good knowledge of durability and that the durability of a transcatheter valve will be similar to a surgical valve, then I think the uptake of TAVI will increase even further and then the discussion will shift to lifetime management,” he concludes.