A trial led by Dr. Holger Thiele showed that there was no difference in outcomes by 30 days when comparing the use of self-expandable and balloon-expandable valves in transcatheter aortic valve implantation (TAVI). The findings of this study published in the European Heart Journal suggest that both can be safely used in the majority of the population.
Trials have demonstrated that TAVI can be a safe alternative to surgical aortic valve replacement in patients who are at a high, intermediate or low surgical risk. Although TAVI has been shown to be safe, it comes with its own restrictions. These include the inability to retrieve or reposition the valve after it has been fully expanded, the occurrence of paravalvular leak which if severe, has been associated with a higher mortality rate, the possible need for permanent pacemaker implantation, and the occurrence of hemodynamic compromise during placement. The more recent generations of valves have been developed to address these potential issues. Currently, there are two types of valves that have been widely used. These are the self-expanding valve (SEV) and the balloon-expandable valve (BEV). There is a current knowledge gap regarding the difference in outcomes between BEV and SEV. Although there have been a few randomized trials, these may not have been adequately powered to address this question. The investigators aimed to compare the newer generation SEV and BEV with regards to both safety and efficacy in high-risk patients with symptomatic aortic stenosis undergoing femoral TAVI.
The trial enrolled patients who were 75 years of age or older, with symptomatic aortic stenosis, and were considered high risk of surgical aortic valve replacement. A patient was considered high risk if they had a European System for Cardiac Operative Risk Evaluation (EuroSCORE) of 20% or higher, or a Society of Thoracic Surgeons (STS) risk score of 10% or higher, or other high-risk criteria as determined by a heart team consensus. Exclusion criteria included not being suitable for both SEV and BEV, cardiogenic shock or hemodynamic instability, history of endocarditis or an ongoing infection requiring antibiotic treatment. This was a 2×2 factorial trial that compared the newer generation of SEV (Evolut R, Medtronic Inc., Minneapolis, MN, USA) with BEV (Sapien 3, Edwards Lifesciences, Irvine, CA, USA) as well as general and local anesthesia. The primary endpoint of the study was a composite of all-cause mortality, stroke, moderate or severe paravalvular leak, and permanent pacemaker implantation at 30 days.
The study randomized 447 patients to either SEV implantation (225 patients) or BEV implantation (222 patients). Of those patients, 438 underwent TAVI and were eligible for analysis (219 patients in each group). Almost half of each group received local anesthesia and the other half received general anesthesia. With regards to the primary outcome, 5 patients either withdrew consent or were lost to follow up and were not included in the outcome analysis. At 30 days, the rate of the primary outcome was equivalent in both groups (28.4% in SEV and 25.9% in BEV, P for equivalence = 0.04). The findings were also similar in the per-protocol analysis. This was consistent across multiple prespecified subgroups including sex, age, presence of coronary artery disease, left ventricular ejection fraction, type of anesthesia, and body mass index. Rates of all-cause mortality, stroke and moderate or severe paravalvular leak were equivalent between both groups (P for equivalence < 0.05). However, there was a slightly higher rate of permanent pacemaker implantation in the SEV group (23.0% vs 19.2%, P for equivalence = 0.06).
The trial demonstrated that 30-day outcomes between SEV and BEV implantation were equivalent. This is consistent with previously published randomized trials comparing the two valves. However, the investigators noted that the rates of pacemaker implantation in this trial were in the upper range of previous reported trial and registry data. However, while pacemaker implantation is associated with increased costs, longer hospital stays and increased morbidity, it was not associated with increased mortality.
It is important to note that the trial does have its limitations. Blinding was not possible and this may impact outcomes. Additionally, the study only included patients who were at high surgical risk. Finally, the results of this study may not be applicable to patients at low or moderate surgical risk. Although the study demonstrates that both valve types are safe, valve choice should be considered and one valve type may be favored over another in certain scenarios (including severe calcification, bicuspid anatomy or the presence of a horizontal aorta).