Editor's note: Can transcatheter aortic valve implantation (TAVR) result in benefit for low-risk patients?What are its advantages over surgical aortic valve replacement?Perhaps confounded by the 2-year follow-up results of the evolut low risk research published in blockbuster at this europcr 2021 Congress, we invited the principal investigator Professor John K. Forrest, Yale University School of medicine, USA, to a special interview on relevant issues.
International Circulation: At this conference, you announced the results of the 2-year follow-up of the Evolut low-risk trial. Would you please share us what are the updates of the trial?
Professor John Forrest: Thanks for having me, and I am happy to go over some of that. As you know, the EVOLUT Low Risk study looked at people who were low risk for surgical aortic valve replacement, and randomized them one-to-one to either undergo surgical aortic valve replacement or a transcatheter aortic valve replacement with the Evolut valve. The study enrolled just over 1300 patients - 730 in the TAVR arm and 684 in the surgical arm. If you recall, when 850 patients had reached their twelve-month follow-up, the primary endpoint of death or disabling stroke at 24 months was evaluated using Bayesian methods, a predictive method for what would happen. All patients have now had the opportunity to complete their two-year follow-up, and that is what was presented at EuroPCR earlier this week. What we saw in those was that patients continued to do very well out to two years. When we look at the actual data, what we saw was that at two years and looking at the primary endpoint for death or disabling stroke, then that occurred in 6.3% of the patients who underwent a surgical aortic valve replacement, and 4.3% in those who underwent transcatheter aortic valve replacement – an absolute difference of 2%. That certainly met significance for non-inferiority with a p-value of <0.01 for non-inferiority. With regard to superiority, it didn’t quite meet statistical significance. The p-value was 0.08. There have also been concerns in low risk patients about a possible catch up – we recognize in terms of absolute numbers with all-cause mortality or disabling stroke that transcatheter patients early on tend to do better, and that between years one and two there is a catch up such that the surgical patients do better. So we did a landmark analysis within this study, and we found that wasn’t the case for this Evolut valve. Between years one and two, with regard to all-cause mortality or disabling stroke, that occurred in 1.9% of the patients who underwent a transcatheter aortic valve replacement, and 2.1% of the patients who underwent a surgical aortic valve replacement.
International Circulation: In terms of pacemaker implantation and "mild paravalvular leak", the surgical group is better than TAVI. What changes do you think this will bring to clinical diagnosis and treatment?
Professor John Forrest: When you look at secondary outcomes, there are clearly some differences. You highlighted two of them that are in favor of surgical valve replacement, and they are pacemaker rate and greater-than-or-equal-to-mild paravalvular leak. That is very true. It is important to note that the incidence of moderate or severe paravalvular leak, which has been shown to have a clinical impact, was extraordinarily low in both the transcatheter arm and the surgical arm. But there is more mild paravalvular leak. What impact that has over the long term, we will have to see. We don’t really know. Some studies suggest it won’t have much of an impact, but I think it is too early to draw that conclusion. What is the impact of having a pacemaker long term? We will have to see there as well. Certainly, for younger patients, batteries can wear out after a decade or so, so let’s see what happens there. I think, similarly, there are advantages with the Evolut valve for these secondary outcomes when you look at hemodynamics or when looking at patient prosthesis mismatch, you see that the transcatheter valve is better. How is that going to translate long term? We also don’t know how these different variables will balance each other out. That is why it is important to study these patients for a long time.
International Circulation: Would you please share us what is the research direction of the next stage of this research?
Professor John Forrest: The next stage is to continue to follow these patients out. We can be very reassured that the patients are doing well at two years. I think we can also be reassured that heart teams are doing an excellent job of choosing the appropriate patients to undergo these therapies. Certainly, this doesn’t apply to 100% of low risk patients. Some low risk patients will have anatomy that is too small with regard to the sinus of Valsalva to safely undergo a transcatheter valve procedure, or they may have coronary heights that are exceptionally low, in which case you only give consideration. Heart teams are recognizing this. Heart teams are recognizing that in a small number of patients, there may be massive amounts of calcification and calcium really needs to be debulked in order to achieve an optimal implant. But for the majority of low risk patients, I think that we can be reassured here. But we need to see what happens. We need to see what happens at ten years. We need to see what happens at five years. We need to continue to evaluate these patients and report on their outcomes.
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