The main findings of the present 10-year follow-up after TAVI with the self-expanding CoreValve system are a low actual rate of bioprosthetic valve failure and structural valve deterioration, as well as a signal of durable valve hemodynamic performance.
TAVI has developed rapidly and has become the standard treatment in elderly patients with severe symptomatic aortic valve stenosis who are at high or prohibitive risk for surgery [
13]. The universal trend toward expanding TAVI to low-surgical-risk and relatively younger patients raised concerns and questions about the durability of THVs. As low-surgical-risk patients are mostly young with longer life expectancy as well as a higher risk for biological valve degeneration, the issue of durability is most important before deciding to implant THV in those groups of patients [
14]. In this study, patients who underwent TAVI with a CoreValve system were followed up to 10 years in order to evaluate the durability of this system.
Bioprosthetic Valve Failure and Structural Valve Deterioration
Experience with early-generation surgical bioprosthetic valves showed that SVD commonly begins 8 years after implantation, with a greatly increased rate of SVD after 10 years [
15,
16]. Studies on the performance of surgical valves during the first decade following valve implantation have reported rates of freedom from SVD at 10 years > 85% [
17‐
19]. Currently, long-term outcomes with second-generation porcine Hancock II valve (Medtronic) documented survival rates without SVD at 10, 15, and 20 years of 95%, 75%, and 49%, respectively [
20]. The present study evaluated the early-generation transcatheter self-expanding CoreValve system and showed an actual survival rate without BVF and SVD at 10 years of 96.1% and 97.9% (actual rate), respectively.
As TAVI has only been widely available since 2007, data concerning long-term durability are limited [
9]. A large FRANCE-2 registry, which included 4201 patients after THV implantation, reported a cumulative rate of severe and moderate SVD at 5-year follow-up of 2.5% and 13.3%, respectively [
21]. Another study which included only patients who underwent TAVI with the CoreValve system reported a 5-year rate of SVD of 1.4% [
6]. Our study reported a lower actuarial rate of SVD at 5 and 6 years compared with the previously mentioned studies, with rates of 0.8% and 2.4%, respectively.
The incidence of SVD 5 to 10 years post-TAVI was described in the UK TAVI registry, where severe SVD occurred in 0.4% at a mean of 5.3 years after implantation, while moderate SVD was reported in 8.7% of patients [
22]. Sathananthan et al. performed a 10-year follow-up in high-risk patients who were treated during the early experience of TAVI and found that the rate of SVD at 4, 6, 8, and 10 years was 0.4%, 1.7%, 4.7%, and 6.5%, respectively [
23]. Compared with the previously mentioned studies (which used the cumulative incidence to assess the SVD), the present study observed a lower actual rate of SVD and BVF at 10 years of 2.1% and 3.9%, respectively. This difference could be attributed to the implantation of different THV, as a balloon-expandable valve was implanted in 98.3% of patients in the previous study.
The NOTION (Nordic Aortic Valve Intervention) trial is the first to compare only low- risk patients with severe AS who were treated with TAVI using first- and second-generation CoreValve systems versus surgical aortic valve replacement [
24]. NOTION reported a low 10-year cumulative incidence of severe SVD of 1.5%, and a 10-year cumulative incidence of BVF of 9.7% [
24]. Our study reported an actual rate of severe SVD at 10 years of 2.1% and BVF of 3.2%. We observed a higher rate of severe SVD than that reported in the NOTION trial but a lower BVF rate. We included nearly double the number of patients, which may explain the higher rate of severe SVD in our analysis. The higher rate of BVF reported in the NOTION trial was mainly driven by the higher valve-related death (5%) than in ours. Despite the high all-cause mortality in our study, we reported only three valve-related deaths. The NOTION trial enrolled low-risk patients, in contrast to our study, which included 59.3% of patients with intermediate and high surgical risk.
These findings together raise the question of whether the continuous improvement of newer-generation valves leads to a lower rate of degeneration and failure. In the PARTNER 2A trial, the rate of SVD with the older-generation SAPIEN XT was high (9.5%), but with the newer-generation SAPIEN 3, the 4-year SVD was only 2.5% [
9]. It is also recognized that differences in durability exist between different bioprosthetic surgical aortic valve designs and generations [
16‐
19]. As newer generations of THV have anti-calcification treatment of leaflets, improvement in leaflets and frames, and the addition of a skirt at the lower part of most valves [
9], we assume that the rate of SVD will continue to decline. However, more data are still needed to confirm these results, particularly in low-risk patients.
Our study reported a nonsignificant difference in transvalvular gradient and effective orifice area during the 10 years of follow-up. Although these findings were similar to what was documented by the NOTION trial and the study by Sathananthan et al., we should interpret these results with caution due to the high mortality rate [
23,
24]. The current analysis reported a high rate of mortality at 10 years (89.8%), which is not surprising because the cohort of our study consisted of a population in their 80s with a relatively limited further life expectancy and multiple comorbidities. We compared the baseline and periprocedural data between patients who were still alive at 10 years and who had died, and we found a trend toward higher pro-BNP, more severe aortic valve stenosis, and a higher rate of significant post-TAVI AR among non-survivors. The higher baseline peak pressure gradient, reduced LV EF, high baseline pro-BNP, and SVD were predictors for all-cause mortality at univariable analysis, while only post-TAVI acute kidney injury was the independent predictor of all-cause mortality. It is notable that our data do not reflect the contemporary outcomes, as they came from early experience. Comparing the periprocedural complications among different time intervals revealed improved rates of life-threatening bleeding and major vascular complications. Despite the improvement in periprocedural complications, the mortality rates did not decline. These findings together indicate that the mortality in the study population was multifactorial and related to the multiple comorbidities.
Study Limitations
Although the follow-up in the current study was 88.4%, the analysis is limited by the high mortality rates at 10 years in an elderly high-risk population. We tried to overcome this problem by computing the cumulative incidence to compete for high all-cause mortality. The main cohort of our study consisted of a population in their 80s with a relatively limited further life expectancy, so the results would be less useful in a younger population with lower procedural risk and fewer comorbidities. Additionally, the echocardiographic follow-up was relatively limited, which might underestimate the incidence of SVD (echocardiography was available in 69.4%, 77.8%, and 82.4% of patients at 5, 7, and 10 years).