Transfemoral transcatheter aortic valve implantation (TAVI) has demonstrated similar results as well as superiority over surgical aortic valve replacement (SAVR) in low-to-high surgical risk elderly patients with tricuspid aortic valve (TAV) stenosis1. TAVI is now the gold standard for patients at high surgical risk or who are deemed inoperable and is favoured over SAVR in patients at intermediate risk who are suitable for a transfemoral approach1. Conversely, the European Society of Cardiology (ESC) guidelines recommend surgery as the preferred option for patients with severe aortic stenosis (AS) and a bicuspid aortic valve (BAV) anatomy as these patients were excluded from previous randomised controlled trials (RCTs)1.
Despite the lack of randomised comparative studies with SAVR, TAVI is already frequently used in AS patients with BAV. In 2020, they represented ≥10% of patients undergoing TAVI in the Western population2. This use is supported by several registries, including the very large Society of Thoracic Surgeons (STS) registry, which shows that for BAV patients considered suitable for TAVI, the acute results and 1-year follow-up of those receiving either the balloon-expandable (BE) SAPIEN 3 (Edwards Lifesciences) or the self-expanding (SE) Evolut-R/Pro (Medtronic) transcatheter heart valve (THV) are as good as patients with tricuspid AS receiving the same THV34. These favourable results were recently confirmed in BAV patients at low surgical risk25. As a result, the BE-THV SAPIEN 3 and the SE-THV Evolut-R/Pro have received Food and Drug Administration (FDA) and “European Conformity” (CE) approval for all surgical risk, regardless of the valve anatomy, and the precaution regarding BAV has recently been removed from its commercial labelling6.
To guarantee good acute procedural and 1-year results, several aspects have been clarified during the last few years. First, we must avoid proposing TAVI for patients with type 1 BAV with both calcified raphe and excessive calcified leaflets7; second, we must avoid proposing TAVI for patients in whom surgery of the aortic root is required; third, the procedure should be feasible through transfemoral access; fourth, the size of the device should be adapted to the smallest diameter of the aortic root-aortic valve complex which, in 20% of cases, is a few mm above the annular plane, and finally, we may consider using embolic protection devices, particularly in younger patients6.
It is important to remember that in Western countries, BAV is frequent among patients with AS requiring valve replacement, regardless of age. They represent 28% of those >80 years old and 42% of those between 70 and 80 years old8. It is also important to remember that the vast majority of those BAV patients undergoing SAVR undergo a relatively “simple surgery” including bioprosthetic replacement without combined aortic root surgery6. Therefore, in BAV patients undergoing such “minimal” SAVR, TAVI has the potential to provide the same medical service.
One important reason not to propose TAVI for more BAV patients is the lack of information concerning long-term results and THV-durability in this very peculiar context. Such data are indeed scarce and limited to valve haemodynamic performance over a relatively short period of time9. In the BAVARD registry, 30 days post-TAVR, the indexed effective orifice area (EOA) was smaller in BAV patients than in TAV patients, but the incidence of severe prosthesis-patient mismatch was similar10. In the STS/ACC TVT registry, the 1-year mean gradient and rate of ≥moderate paravalvular regurgitation (PVR) were similar between BAV and TAV patients treated with the SAPIEN 34. The BAVARD registry was also reassuring on the overall THV stent circularity. However, THVs were more constrained and underexpanded in BAV patients compared to TAV patients10. As prosthesis expansion could impact the THV durability and promote leaflet thrombosis, these findings raised concerns about a potential acceleration of the structural valve degeneration process in BAV patients6. A recent CT-scan study found hypoattenuated leaflet thickening in 10% of BAV patients 30 days post-TAVR, which is comparable to the findings of previous TAV studies9.
The study by Zhou et al, published in the present issue of EuroIntervention, reports on the 3-year clinical and echocardiography outcomes of 246 consecutive patients undergoing TAVI, mostly treated with SE-THVs (82.9%) in a Chinese centre11.
The present study has several important limitations. First, it reports data from a single centre. Second, it reports data from an Asian population with a higher frequency of BAV than is found in Western countries and with a different proportion of BAV subtypes (0 versus 1)6. Third, among the SE-THVs which were used in the study besides the CoreValve (Medtronic) family, several are not available in Western countries, including the supra-annular Venus A (Venus Medtech), the VitaFlow (MicroPort), and the intra-annular TaurusOne (Peijia) THVs. It is also unfortunate that the proportion of patients treated with each of these three different SE-THVs is not reported.
Still the authors should be congratulated as it is the first study to report on the 3-year clinical and echocardiography outcomes in BAV patients undergoing TAVI11, for they add several important pieces of information. The study demonstrates that at 3 years, survival (87.2% versus 79.6%; p=0.11), transvalvular gradient (10.76±5.15 mmHg versus 10.33±4.74 mmHg; p=0.64), and paravalvular leak ≥moderate (3.9% versus 6.5%; p=036) are similar between BAV (n=109) and TAV (n=137) patients. It further shows a progressive and continuous decrease of left ventricular mass over the 3-year time period.
As the proportion of type 0/type 1 BAV is very different between Western (15%/85%) and Asian (60%/40%) AS patients undergoing TAVI6, it is also very reassuring to observe that the 3-year clinical outcome and valve haemodynamic performance, as evaluated by echocardiography, were similar in patients with type 0 or type 1 BAV.
Also interesting is the subgroup analysis restricted to the 204 patients treated with an SE-THV showing no sign of degradation in haemodynamic performance at 3 years in BAV as compared to TAV patients. This information is also reassuring in the context of the recent report that, in TAV patients, structural valve deterioration at 5 years is less frequent in patients undergoing TAVI than in those undergoing SAVR (2.6% versus 4.4%). This was recently reported, but not yet published, in the combined analysis of the 2 pivotal randomised studies comparing SE-THVs (CoreValve and Evolut TAVI systems).
Such very favourable results are encouraging and will have to be confirmed in larger patient populations, as well as in BAV patients from Western countries. It will also be very important to report long-term outcomes and valve durability of BE-THVs, as they are often preferred over SE-THVs in this population6, whereas their durability has recently been questioned in TAV patients1213.
If the favourable results reported in the present study are confirmed, TAVI could become the treatment of choice for most AS patients with BAV. While BAV already represents 10% of patients undergoing TAVI in Western countries6, this proportion could climb to 40% if the use is extended to patients in the 70-80 year-old range.
Conflict of interest statement
The authors have no conflicts of interest to declare.
Supplementary data
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