Multiparametric evaluation of percutaneous mitral valve repair (Mitraclip) after 3 months

Background. MitraClip (MC) therapy is now established as a secure, feasible treatment option for patients with severe mitral regurgitation (MR) at high surgical risk. The efficacy of the percutaneous approach, especially in patients with functional disease, has been evaluated in a large number of studies, but the endpoints used to establish the success of this procedure over the surgical ones were based on unreliable, less standardizable measures. Purpose. This study sought to evaluate the efficacy of MC therapy in terms of new functional outcomes, comparing data related to degenerative mitral regurgitation (DMR) and functional mitral regurgitation (FMR). Methods.. Between October 2010 and November 2016, 91 consecutive patients with severe MR and not eligible for surgical mitral valve repair were assessed before MC implant using echocardiogram, BNP assay, non-invasive measurement of cardiac output (CO) with inert gas rebreathing technique, and cardiopulmonary exercise test (CPX). The same tests were used for follow-up steps at 3 months after the procedure. Results. MC implant rate was 95%. Immediate success with reduction of MR to ≤2+ was observed in 86.7% of cases. In both organic and functional populations, a significant reduction of MR from baseline with was observed (p<0.001). NYHA functional class showed a significant improvement over three months in both groups. Significant left ventricular (LV) remodeling was observed only in groups (LV End-diastolic Volume in FMR was 211±62 mL at baseline, 190±77 mL at 6 months, p=0.003; in DMR was 123±33 mL at baseline, 103±35 mL at 6 months, p<0.001). LV End-systolic volume (LVESV) also showed a significant reduction at 1 month only in the functional group (LVESV in FMR was 135±55 mL at baseline, 123±67 mL at 1 month, p=0.027). Systolic pulmonary pressure values were significantly reduced from baseline in the population with the functional disease (PAPs was 46±11 mmHg at baseline, 38±8 mmHg at 6 months, p=0.005); in the degenerative group, PAPs showed small variations (42±11 mmHg at baseline and 39±9 mmHg at 6 months, p>0.05). CO and cardiac index (CI) increased significantly at rest (CO 3±0.7 L/min at baseline, 3.6±0.9 L/min at 6 months; CI 1.64±0.42 L/min/m² at baseline, 2±0.4 L/min/m² at 6 months, both p=0.01) and during cardiopulmonary exercise test (CO 4.9±1.7 L/min at baseline, 6.3±1.5 L/min at 6 months; CI 2.71±0.98 L/min/m², 3.44±0.90 L/min/m², both p=0.023) in the functional group. On the other hand, the population with degenerative disease did not present any improvement (CO at rest was 2.9±1.2 L/min at baseline, 2.9±0.8 L/min at 6 months, p=0.53; CO during exercise was 6.4±3.5 L/min at rest and 6.6±3 L/min at 6 months, p=0.51). Oxygen consumption, anaerobic threshold, and other functional parameters were measured during cardiopulmonary exercise test and showed an improving trend (see Table 1). Heart rate and arteriovenous oxygen difference did not show significant changes both at rest and during exercise. Conclusions. MitraClip device reduced MR and produced a significant left ventricular reverse remodeling over 6 months in both the populations treated. Functional outcomes, as the implement of cardiac output and cardiac index at rest and during cardiopulmonary exercise test, proved the efficacy of the percutaneous mitral valve repair in patients with functional mitral regurgitation. Observing the concurrent absence of significant variation of heart rate, the improvement of cardiac output could be attributed only to an increase in stroke volume (SV). At the same time, the stability of arteriovenous oxygen difference values further demonstrated that the increase in oxygen consumption is due to an increase in cardiac output rather than to a greater peripheral extraction.