Transcatheter Mitral Valve Implantation: A Systematic Review of Available Devices, Clinical Outcomes, CT-Based LVOT Planning and Outcomes in Mitral Annular Calcification

Background: Transcatheter mitral valve implantation (TMVI) represents an evolving therapeutic strategy for patients with severe mitral valve disease who are at high or prohibitive risk for conventional surgery. Since the first human implantation in 2012, multiple dedicated and adapted devices have entered clinical investigation, yet only one dedicated system—the Tendyne prosthesis (Abbott Structural)—holds regulatory approval. This systematic review evaluates the current landscape of available and emerging TMVI devices, examines the clinical outcome data, discusses key indications and limitations, analyses the role of computed tomography (CT) in predicting left ventricular outflow tract (LVOT) obstruction caused by the unopposed anterior mitral leaflet, and compares TMVI outcomes with conventional surgical mitral valve replacement (SMVR) in the specific context of severe mitral annular calcification (MAC). Methods: A systematic search of PubMed, EMBASE, Cochrane Central, and Web of Science was performed for studies published from January 2010 to March 2025 reporting outcomes of TMVI in native valve disease, valve-in-valve (ViV), valve-in-ring (ViR), or valve-in-MAC (ViMAC) procedures. Studies reporting CT-based LVOT planning, neo-LVOT quantification, and LVOT obstruction outcomes were specifically sought. Meta-analyses comparing TMVI with redo surgical mitral valve replacement were included. A total of 63 studies (n > 12,000 patients across all subgroups) were included in the qualitative synthesis; 28 studies were included in the quantitative synthesis. Results: Nine dedicated TMVI devices are currently under clinical investigation, with only Tendyne holding CE Mark and FDA approval. In ViV/ViR cohorts, TMVI was associated with significantly lower in-hospital mortality (OR 0.72, 95% CI 0.57–0.92; p = 0.008) and 30-day mortality (OR 0.49; p = 0.04) compared with redo SMVR, with no significant difference at one year (OR 1.03; p = 0.91). In ViMAC cohorts, 30-day mortality ranged from 14 to 24%, which was substantially higher than in the ViV outcomes. CT-based virtual simulation of the neo-LVOT area—the residual outflow tract created by anterior mitral leaflet displacement—is the most validated predictor of LVOT obstruction, with a threshold of ≤1.7 cm2 yielding 96% sensitivity and 92% specificity. The LAMPOON technique (laceration of the anterior mitral leaflet to prevent outflow obstruction) has expanded the eligibility for patients who were previously excluded due to LVOT risk. Surgical MVR in severe MAC carries a median 30-day mortality of 6.3% (range 0–27.3%), while ViMAC TMVI with dedicated devices yields 6.8% 30-day mortality, without a definitive randomised comparison. Conclusions: TMVI offers a viable alternative to redo surgery in high-risk patients with failed bioprostheses or rings. In severe MAC, both surgical and transcatheter approaches carry significant risk; patient selection, CT-guided LVOT planning, and use of dedicated devices are critical to optimising outcomes. The ongoing SUMMIT randomised controlled trial will provide the first high-quality comparative data. Future developments in transseptal delivery and LVOT-safe device architectures are expected to broaden the eligible population.