Mitral valve repair and bioprosthetic implantation are the most frequently performed procedures in adult patients requiring mitral valve surgery. These procedures avoid permanent anticoagulation therapy and improve patients’ quality of life. However, with extended life expectancy, prosthetic degeneration and the need for subsequent invasive procedures have become increasingly common. Conventional surgical reoperation remains the most widely employed technique, though it carries perioperative risks associated with both technical aspects and additional morbidities compared to the original procedure. Recently, compassionate use of transcatheter valves in the mitral position (known as “valve-in-valve” or “valve-in-ring”) has emerged as a less invasive option, as analyzed in a meta-analysis published last year on our blog. Additionally, we examined the current status of transcatheter mitral prostheses in a review from 2023.
Ten German centers participated in this multicenter registry, providing data from 273 patients with prosthetic or annuloplasty repair degeneration treated with mitral valve-in-valve/ring (ViVM, 79 patients) or conventional reoperation (redo-mitral, 194 patients) between 2014 and 2019. Patients with prosthetic endocarditis and dysfunctional mechanical prostheses were excluded. Data were retrospectively analyzed with propensity score matching. The primary endpoint was mortality at 30 days and midterm, with perioperative outcomes evaluated according to Mitral Valve Academic Research Consortium (VARC) criteria. Additionally, the influence of moderate or greater tricuspid regurgitation (TR) on mortality at 30 days and midterm was analyzed.
The results showed no significant mortality differences between the ViVM and redo-mitral groups. However, baseline characteristics differed, such as age and the presence of atrial fibrillation and moderate or greater TR. ViVM was associated with shorter procedural times and ICU stays. Redo-mitral allowed for larger prosthesis sizes (average 2 mm increase) and addressed concomitant lesions (30 concomitant procedures were reported). In both groups, moderate or greater TR was an independent predictor of mortality at 30 days and midterm.
The study concludes that while prosthetic replacement surgery remains the treatment of choice, ViVM may be an attractive alternative for high-risk surgical patients.
COMMENTARY:
This is the first German registry presenting and comparing outcomes of ViVM implantation versus reoperation to treat degenerative mitral valve bioprostheses/annuloplasty repairs. However, this study is not without limitations. It is a multicenter, retrospective study, carrying inherent biases and data collection and analysis limitations. Selection bias is evident regarding treatment group allocation; nonetheless, it is emphasized that therapeutic decisions were made following individual, multidisciplinary assessments by the Heart Team of each participating center. Additionally, the inability to present uniform echocardiographic data due to the multicenter nature of the study is acknowledged.
A noteworthy finding of this registry is that moderate or greater TR was an independent mortality predictor in both groups, a finding extensively corroborated in other studies. The group led by Szlapka et al. advocates that while it cannot address all coexisting comorbidities, transcatheter therapy focusing solely on the mitral prosthesis offers a benefit due to its limited invasiveness. Future studies on larger populations with extended follow-up are necessary to clarify therapeutic options for this patient subgroup.
Undoubtedly, the revolution brought by the advent and consolidation of TAVI will extend to the mitral valve. ViVM presents a promising, disruptive alternative for managing patients with mitral pathology, which is just around the corner. However, its implantation poses unique challenges, making it more complex and less reproducible than TAVI. On one hand, it requires a transseptal access route, which is complex and not always feasible, thus renewing the importance of transapical access. The risk of left ventricular outflow tract obstruction remains the Achilles’ heel of this technique, although the presence of a similarly-sized prosthesis mitigates this risk compared to implantation in native valves. Prosthesis migration occurs more frequently due to the higher closing pressure of the mitral valve than those observed in the other three valvular positions. Overall, with appropriate planning, this procedure offers a real, less complex alternative to conventional surgery, with hemodynamic outcomes comparable to those of a surgical prosthesis in terms of gradients and residual leakage. Therefore, it should be considered a viable and safe alternative to include in our therapeutic arsenal.
Current results support the effectiveness of the percutaneous approach, especially for high-risk surgical patients. However, it is also essential to maintain a realistic perspective on the future of mitral reoperations. While advances in percutaneous procedures offer new therapeutic options, there will still be cases where conventional surgery remains necessary and irreplaceable: endocarditis, prosthetic thrombosis, small prostheses, mechanical prostheses, etc. Nonetheless, we must keep in mind that in this era of transcatheter therapy, percutaneous mitral valve treatment is on the rise, and it is crucial to be prepared to adapt to these advances and harness their potential to provide the best therapeutic option tailored to each patient type.
REFERENCE:
Szlapka M, Hausmann H, Timm J, Bauer A, Metz D, Pohling D, et al.; Arbeitsgemeinschaft Leitender herzchirurgischer Krankenhausärzte e.V. (ALHK) Study Group. Transcatheter mitral valve implantation versus conventional redo surgery for degenerated mitral valve prostheses and rings in a multicenter registry. J Thorac Cardiovasc Surg. 2024 Mar;167(3):957-964. doi: 10.1016/j.jtcvs.2022.07.032.
