Cardiac remodelling and clinical outcomes following surgical and transcatheter mitral valve interventions

Introduction Primary mitral regurgitation (PMR) causes left atrial (LA) and left ventricular (LV) dilatation, with subsequent LV hypertrophy1,2. In treating PMR, MV repair (MVr) is recommended over MV replacement (MVR) if possible2. Transcatheter edge-to-edge repair (TEER) is reserved for those at high surgical risk. MV intervention (MVI) causes significant reductions in LA and LV size, with cardiovascular magnetic resonance imaging (CMR) considered the gold standard to assess LA and LV size and function. Prior work shows similar reverse remodelling following MVr or MVR, but comparison with patients post-TEER has not been assessed before with CMR3. Purpose To assess reverse remodelling processes in patients with PMR undergoing MVr, MVR or TEER using CMR, to assess differences post MVI. Methods This was a prospective single centre study of patients with severe PMR listed for MVI. Severe PMR was confirmed on echocardiography prior to recruitment, and type of MVI decided by the local multidisciplinary Heart Team2. Patients with secondary MR, significant aortic valve disease, and New York Heart Association class IV were excluded. Participants underwent 6-minute walk test (6MWT) and CMR within 1-month prior to MVI, and 6-months after. CMR protocol included cine and phase contrast imaging. Results One hundred and one patients were recruited. Patients undergoing TEER were significantly older, with higher rates of diuretic use. TEER patients also had higher surgical risk scores, and worse baseline 6MWT (table-1). There were no significant differences between the groups in LV size or function, by indexed LV end-diastolic volume (LVEDVi) and effective forward LV ejection fraction (EF-LVEF) (table-1). There were no significant differences in LA size or MR severity in the three groups. Patients underwent MVR (n=40), MVr (n=43) and TEER (n=18). Patients post-TEER had significantly more residual MR compared to MVR or MVr (table-2). Despite this there were no significant differences in LVEDVi, indexed LV mass, or EF-LVEF between the three cohorts. LA and RA sizes were significantly larger in the TEER cohort, with significantly more TR at visit 2. All three cohorts had significant reductions in LVEDVi and EF-LVEF post-MVI (table-2). All three groups had significant reductions in MR severity, but only MVR and MVr cohorts had significant reductions in LA size. All groups had significant improvements in patient reported quality of life and 6MWT (table 2). The TEER cohort had significantly higher all-cause and cardiovascular mortality over a median 5.5-year follow-up. Conclusion This study demonstrates patients undergoing TEER had significantly more residual MR than with other MVI modalities. Despite higher levels of residual MR with TEER, LV reverse remodelling post-MVI is similar regardless of MVI. LA reverse remodelling was only seen after MVR or MVr. Whilst larger studies are required, these data may affect future TEER use.