Mitral bioprosthesis degeneration is a challenge we wish we never had to communicate to any patient. Many cardiac surgeries were traditionally considered “once-in-a-lifetime” interventions, effectively addressing the heart condition and extending the patient’s survival without further procedures. The currently available mitral bioprostheses demonstrate excellent durability, with some series showing over 85% of patients with functional preservation exceeding 20 years. Criteria for defining structural degeneration of bioprostheses have evolved in recent years, especially with the introduction of TAVI as a therapeutic option. However, beyond these technical criteria, symptomatic bioprosthesis degeneration (causing heart failure and/or hemolysis) presents a reoperation challenge due to the inherent complexities of repeat surgical interventions.

As the preference for bioprosthetic implantation continues to grow, the need for reinterventions will increase, compounded by earlier surgical indications and a progressively reduced tolerance for suboptimal bioprosthesis performance—conditions previously managed medically due to the complexity of reoperations. Minimally invasive approaches that avoid the median sternotomy could emerge as a promising alternative. In the quest to minimize invasiveness, TAVI, initially used on a compassionate basis, has gained popularity as a valve-in-valve (ViV) mitral solution.

ViV is primarily performed using a transapical (retrograde) access, although it can also be accessed through the transeptal approach via peripheral femoral vein access (antegrade). To assess the benefits of this alternative compared to conventional surgical reoperation, the authors conducted a systematic review of PubMed, EMBASE, Cochrane, and Google Scholar, with their registration in PROSPERO, the international database for health-related systematic reviews. Using rigorous methodologies (bias and quality analysis with the Newcastle-Ottawa scale), six comparative studies were identified. These studies analyzed preoperative characteristics of patients allocated to each treatment option, with primary outcomes focusing on mortality during perioperative periods, at one month, and at one- and two-year follow-ups. Secondary outcomes examined post-procedure complications (stroke, myocardial infarction, bleeding, acute kidney injury, permanent pacemaker requirement, and hospital stay) and residual transprosthetic mean gradient after correcting prosthetic dysfunction.

All studies were retrospective observational, with two of them employing propensity score matching. A total of 707 patients were included in the analysis. Reoperations were performed via median sternotomy, while ViV procedures were conducted using transseptal and transapical access routes nearly equally. In most reoperations, a new bioprosthesis was implanted, while ViV predominantly used the balloon-expandable Edwards SAPIEN prosthesis across its various iterations. Despite the older age and higher comorbidity burden in ViV patients, mortality rates for hospital stays (OR = 0.52; p = .14), 30-day mortality (OR = 0.65; p = .15), one-year mortality (OR = 0.97; p = .89), and two-year mortality (OR = 1.17; p = .60) were comparable with the conventional surgery group. ViV was associated with a lower incidence of adverse perioperative events such as stroke (OR = 0.31; p = .03), bleeding (OR = 0.21; p < .00001), acute kidney injury (OR = 0.43; p = .01), permanent pacemaker requirement (OR = 0.18; p = .005), and shorter hospital stay (mean difference = -0.64 days; p < .00001). Only the transprosthetic gradient marginally but significantly favored the new surgical prostheses (mean difference = 0.25 mmHg; p = .04), considering both bioprosthetic and mechanical prostheses implanted after removal of the degenerated biological prosthesis.

The authors concluded that ViV was associated with better outcomes compared to prosthetic mitral valve reoperation in patients with degenerated mitral bioprostheses, with lower perioperative complication rates and shorter hospital stays, and without significant differences in mortality rates.

COMMENTARY:

This quantitative review updates the role of percutaneous approaches for degenerated mitral prostheses. Current evidence is based on recent retrospective studies, given the novelty of the procedure. However, research in percutaneous treatment for mitral valve pathology is gaining traction and is expected to disrupt patient management similarly to TAVI’s impact on aortic stenosis treatment in the coming years.

The ViV procedure has unique aspects that make it somewhat more “surgical.” First, the larger size of the mitral valve limits device maneuverability, making the transeptal approach more aggressive than for other procedures like balloon valvuloplasty or edge-to-edge therapy. This has renewed interest in the transapical approach, which had been unfairly sidelined due to TAVI’s success. Secondly, implantation within the existing bioprosthetic frame renders it more predictable and safer than implantation in rings (valve-in-ring) or native valves (transcatheter mitral valve implantation or TMVI, valve-in-MAC, etc.) where the anterior leaflet remains intact. The risk of left ventricular outflow tract obstruction, the main concern of the procedure, is mitigated by the existing prosthesis that occupies a similar position to where the TAVI device will be deployed. Nevertheless, this should not be misconstrued; the obstruction risk remains but is more predictable in pre-procedure models than with native mitral valve implants. Although leaflet laceration, as seen in aortic procedures to prevent coronary ostia occlusion, is theoretically possible in ViV, it remains anecdotal. If, after adequate planning, the procedure is deemed feasible, avoiding the complexities and risks of surgical reoperation and cardiopulmonary bypass with an implant that demonstrates almost comparable hemodynamics to surgical prostheses in terms of gradients and residual leaks makes it a viable therapeutic alternative to be integrated into our therapeutic arsenal.

The results support this treatment option, particularly in high surgical risk patients, as well as in cases where the known durability of TAVI device biological tissue is not a concern. The use of balloon-expandable devices is almost mandatory, and in the future, we may see some adapted for ViV, as is done for the aortic valve. However, its use remains compassionate and restricted. Large-scale randomized trials are required to mitigate biases and validate these findings. This meta-analysis highlights the need to act proactively rather than wait and observe. We must incorporate these techniques into daily practice to stay competitive when the next “PARTNER I” trial for transcatheter mitral therapy arrives.

Does this mean mitral reoperations are a thing of the past? Absolutely not. Patients at low risk will continue to undergo reoperations where residual gradients matter, such as those with 25 mm mitral bioprostheses or mechanical prostheses with pannus/thrombosis, where TAVI device durability, left ventricular outflow tract obstruction risk, or prosthetic endocarditis are concerns. This broadens the spectrum of therapeutic options tailored to patient needs, with insufficient knowledge or reluctance no longer justifying the exclusion of these options. Offering them requires collaboration with our cardiologist colleagues. The mitral bastion is starting to become less of a stronghold. Only training, continuous updates, critical evidence review, and open discussion will lead us to success. We boarded the TAVI train late for aortic treatments… let’s be on time for mitral.

REFERENCE:

Ismayl M, Abbasi MA, Mostafa MR, Aboeata A, Vora AN, Ben-Dor I, et al. Meta-analysis comparing valve-in-valve transcatheter mitral valve replacement versus redo surgical mitral valve replacement in degenerated bioprosthetic mitral valve. Am J Cardiol. 2023;189:98-107. doi:10.1016/j.amjcard.2022.11.043.