Background: Transcatheter mitral valve implantation (TMVI) is a novel therapeutic alternative for high-risk patients with severe secondary mitral regurgitation (SMR), who are considered suboptimal candidates for open-heart surgery and transcatheter edge-to-edge repair (TEER). Preliminary study results of patients treated with TMVI are promising, however data comparing outcomes of TMVI versus routine TEER has not been provided yet.

Methods:

The global, retrospective CHOICE-MI registry included a total of 156 patients with severe SMR that were treated with ten different TMVI devices (mostly transapical access) between 05/2014 and 03/2021. All patients were considered ineligible for both surgery and TEER. From 11/2008 until 09/2019, the European multicentre EuroSMR registry included a total of 1676 patients with severe SMR, who underwent TEER after interdisciplinary heart-team consensus. Propensity-score matching was performed for 12 demographic, clinical and echocardiographic confounders including age, gender, functional status, left and right ventricular function, left ventricular end-diastolic volume, tricuspid regurgitation, pulmonary hypertension, chronic kidney disease, prior myocardial infarction, prior bypass surgery and SMR severity. Clinical and functional outcomes were compared between the matched cohorts. The pre-defined primary endpoint was a combined endpoint of all-cause mortality or heart failure (HF) rehospitalisation after 1 and 2 years.

Results: After propensity-score matching 144 TMVI patients (75.0 years [70.3, 80.0], male gender 64.7%, EuroSCORE II 6.3% [3.7, 13.6], baseline LVEF 39% [32, 45]) were compared to 499 TEER patients (76.7 years [70.0, 80.8], male gender 64.4%, EuroSCORE II 7.5% [3.9, 14.1], LVEF 36% [32, 45]). At discharge and after 1 year, the rates of residual MR ≤1+ were 96.6% and 95.6% after TMVI compared to 63.0% and 48.2% after TEER (both p<0.001, Figure 1). At 1 year follow-up, the extent of functional improvement was more evident in patients treated with TMVI (NYHA class I/II 84.9%, NYHA class III/IV 15.1%) than in those undergoing TEER (NYHA class I/II 64.2%, NYHA class III/IV 35.8%) (p<0.001). Thirty-day mortality was higher after TMVI (9.3%) compared to TEER (4.2%) (p=0.038). There was no difference between TMVI and TEER regarding the primary endpoint after 1 year (cumulative event rate 39.6% [TMVI] vs. 32.6% [TEER], p=0.11) and after 2 years (48.6% [TMVI] vs. 46.1% [TEER], p=0.26) (Figure 2).

Conclusion: Amongst available treatment options for SMR, the role of TMVI has yet to be defined. Based on data from two large multicentre registries, the present study is the first real-world, propensity-score matched comparison between TMVI and TEER for SMR.  Compared to TEER, TMVI was associated with a more predictable elimination of MR after TMVI resulting in symptomatic improvements at least as good as after TEER. While 30-day mortality was higher after TMVI, no significant difference between TMVI and TEER was found for the combined endpoint of all-cause mortality or HF rehospitalisation after 1 year. However, comparability between both groups remains limited, since most patients undergoing TMVI were considered ineligible for TEER. Our results strengthen the body of evidence that TMVI is a valuable treatment option for severe SMR yielding comparable outcomes in patients not amenable to surgery or TEER.