Characteristics and outcomes of patients screened for transcatheter mitral valve implantation: 1-year results from the CHOICE-MI Registry

Aim

A considerable proportion of patients with severe mitral regurgitation (MR) are unsuitable for established surgical or transcatheter therapies. In this setting, transcatheter mitral valve implantation (TMVI) is emerging as a valuable treatment option to effectively address a relevant healthcare burden. As patient selection criteria need to be refined to account for emerging technologies and the role of TMVI in the current landscape of MR treatment options has not yet been established, the aim of the CHOICE-MI registry was to investigate characteristics, actual management and clinical outcomes of patients undergoing TMVI screening process.

Methods

The CHOICE-MI registry is an investigator-initiated, retrospective, international registry, including patients suffering from symptomatic MR ≥2+ who were deemed unsuitable for current MR treatments and entered the TMVI screening process for 10 different devices due to high or prohibitive surgical risk and suboptimal anatomy for transcatheter edge-to-edge repair (TEER). For all patients baseline clinical, echocardiographic, computed tomography characteristics and TMVI screening data were collected. Eligibility to TMVI was assessed by local Heart Teams depending on local and/or clinical trial protocols. Patients considered ineligible for TMVI underwent bailout-TEER, high-risk surgery or medical management, according to local institutional protocols.

• Primary endpoint was a composite of all-cause mortality or heart failure (HF) hospitalisation at 1 year
• Secondary endpoints were all-cause and cardiovascular mortality at 1 year, residual MR and NYHA functional class, at discharge and after 1 year

Results

• Among 746 MR patients screened for TMVI between 2014 and 2021 in 26 centres worldwide, 229 (30.7%) were considered TMVI-eligible and 517 (69.3%) ineligible. Anatomical ineligibility was the most common reason for screen failure (24.9% risk of LVOTO, 34.0% annulus size, 10.9% small left ventricle).
• 229 (30.7%) patients (STS-PROM 5.7%, functional MR 58.4%, MAC ≥moderate 13.0%) underwent TMVI (89.5% trans-apical, 10.5% trans-septal), with 95.2% technical success (1.8% procedural mortality, 3.2% LVOTO, 2.3% valve migration, 9.6% access-site complications). The primary endpoint occurred in 39.2% (26.8% if trans-septal access), MR ≤1+ was observed in 95.2% and NYHA class I-II in 82.7% at 1 year.
• 216 (29.0%) patients (STS-PROM 4.1%, degenerative MR 47.6%, MAC ≥moderate 15.3%) were treated with bailout-TEER, with 86.3% technical success. The primary endpoint occurred in 28.8%, MR ≤1+ was observed in 37.2% and NYHA class I-II in 56.6% at 1 year.
• 61 (8.2%) patients (STS-PROM 2.9%, degenerative MR 71.7%, MAC ≥moderate 34.7%) were referred to high-risk surgery (63% replacement, 37% repair). The primary endpoint occurred in 42.9%, MR ≤1+ was observed in 100.0% and NYHA class I-II in 63.3% at 1 year.
• 240 (32.8%) patients (STS-PROM 5.2%, degenerative MR 58.1%, MAC ≥moderate 33.6%) received medical therapy. The primary endpoint occurred in 47.9%, MR ≥3+ was observed in 87.8% and NYHA class III-IV in 66.0% at 1 year.
• Residual MR ≥2+ after TMVI or bailout-TEER was an independent predictor of the primary outcome.

Main messages

Technological refinements are setting the scene for TMVI revolution, as several devices have been developed, tested, and currently entered the clinical practice. However, as interventional portfolio grows, patient selection criteria need to be updated and refined to frame TMVI in the wide spectrum of transcatheter MR therapies. While data from large-scale prospective studies and clinical trials are certainly awaited, the CHOICE-MI registry represents a relevant attempt to shed light on contemporary use of TMVI devices, moving from patients’ screening process to bailout treatment options for those who are deemed ineligible to such therapy.

Interestingly, despite the growing number of devices, TMVI screening is still a very selective process. In this study, a large proportion of patients (69.3%) failed the selection due to anatomical considerations, including anticipated risk of LVOTO, small ventricular cavity, excessive annular dimensions, and MAC. While in selected cases some of these issues could be addressed using innovative solutions, such as simulation modelling and intentional laceration of the anterior mitral leaflet (LAMPOON) to better assess and prevent LVOTO, some others need to be addressed by device innovation, such as development of novel solutions to tackle large annuli and MAC.

Another relevant issue restraining TMVI from gaining a widespread adoption is represented by device proportions, requiring large sheath sizes, trans-apical access, and carrying a risk of procedure-related complications. Noteworthy in the CHOICE-MI registry, TMVI appeared to be burdened by a relevant incidence of the primary endpoint of all-cause mortality and hospitalization for HF at 1 year compared to bailout-TEER (39.2% vs 28.8%), that could be related to the high proportion of trans-apical procedures (89.5%), beside selection bias and subsequent differences in baseline patients’ features. Indeed, numerically lower rates of the primary endpoint were observed when comparing trans-septal with trans-apical TMVI (26.8% vs 41.3%), therefore, calling for a future transition from trans-apical to trans-septal approach.

Focusing on MR reduction and functional outcomes, data from the CHOICE-MI registry demonstrate that TMVI is an effective, predictable and durable solution for severe MR. On the other hand, in TMVI ineligible patients, bailout-TEER and high-risk surgery, despite being reasonable alternatives to the undesirable outcome offered by the medical therapy, suffer from important drawbacks. Indeed, bailout-TEER resulted in low rates of MR reduction at 1 year (MR≤1+ 37.2%), strengthening the reliability of current TEER selection criteria (these patients have been previously deemed unsuitable for TEER), while high-risk surgery was limited to highly selected cases (8.2%).

Pushing current boundaries of TMVI appears worthwhile in light of the results of the CHOICE-MI registry. Future studies comparing TMVI with TEER or surgery will help clarifying the role of TMVI in current landscape of MR treatment options.