Outcomes of transcatheter edge-to-edge repair for moderate mitral regurgitation

Background The efficacy of transcatheter mitral edge-to-edge repair (M-TEER) has been demonstrated in patients with severe secondary mitral regurgitation (MR). In clinical practice, some patients with moderate MR on transthoracic echocardiography (TTE) are considered to have clinically severe MR based on their clinical course, pulmonary vein flow patterns, transesophageal echocardiography, or stress echocardiography. Outcomes of M-TEER in patients with moderate secondary MR have not been thoroughly investigated. Purpose We aimed to evaluate the impact of M-TEER on clinical prognosis in patients with moderate MR compared with those with severe MR. Methods We assessed consecutive patients who underwent M-TEER for secondary MR between April 2018 and June 2023 in the OCEAN-Mitral registry, a prospective, multicenter registry. Patients were stratified according to MR severity at baseline TTE into two groups: moderate MR (2+) and severe MR (≥3+). The primary endpoint was technical success, defined according to Mitral Valve Academic Research Consortium (MVARC) criteria. Secondary outcomes included hemodynamic parameters during procedure, MR severity, left ventricular volume, hospitalization for heart failure, and mortality. Results Among 2,638 patients, 438 (16.6%) had moderate MR, and 2,200 (83.4%) had severe MR. Among 438 patients with moderate MR, parameters suggestive of clinically relevant MR included severe MR in transesophageal echocardiography (n=146), abnormal pulmonary vein flow pattern (n=304), positive stress TTE (n=118), history of heart failure admission within one year (n=329), and elevated brain natriuretic peptide levels (n=431). Technical success was comparable (97.9% vs. 96.1%, p=0.085). Residual MR ≤ mild was more frequently achieved in patients with moderate MR than in those with severe MR, both at discharge (88.2% vs. 77.3%, p <0.001) and at one month (83.2% vs. 72.4%, p <0.001). At one year, left-ventricular reverse remodeling was modest in moderate MR. Patients with severe MR demonstrated significant reductions in left atrial volume index and tricuspid regurgitation pressure gradient, whereas these changes were not significant in the moderate MR group. The one-year cumulative heart failure hospitalization rate decreased after M-TEER in both groups (moderate MR: from 0.75 to 0.17, p <0.001; severe MR: from 1.21 to 0.21, p <0.001). Patients free from heart failure hospitalization within one year after M-TEER had significantly higher three-year survival compared with those with hospitalization (68.0% [95% CI 65.1-70.8%] vs. 36.4% [95% CI 29.9-43.0%]; log-rank p <0.001). Conclusions In the OCEAN-Mitral registry, M-TEER was safely performed in patients with moderate MR and resulted in a meaningful MR reduction. Although cardiac reverse remodeling was modest compared with severe MR, heart failure hospitalization rates were significantly reduced, suggesting potential benefit in selected patients with moderate MR.