Percutaneous Treatment of Functional Mitral Regurgitation in Heart Failure

Congestive heart failure (HF) remains one of the most important and challenging clinical problems in cardiovascular medicine in Brazil and worldwide. Evidence suggests that mortality in this setting has decreased in Brazil over recent years¹, which may be related, at least partially, to a more intense and widespread use of neurohormonal blockade (with angiotensin-converting-enzyme inhibitors and beta-blockers) in patients with advanced HF². To better evaluate the characteristics of end-stage heart disease in Brazil, the ongoing I Brazilian Registry of Heart Failure (BREATHE registry) will evaluate the profile of 1,200 patients admitted with decompensated HF to 60 hospitals representative of the different Brazilian regions³. Final results of the BREATHE registry are expected to be available within the next months. In spite of recent improvements in medical therapy, advanced HF continues to impose an ominous prognosis; in some subsets, mortality rates can reach up to 30% to 50% in the first year of disease, according to contemporary series of Brazilian centers⁴. In this context, therapeutic alternatives have been intensively investigated in an attempt to improve the outcomes of patients with HF.

Mitral regurgitation (MR) is a frequent finding among individuals with end-stage HF^5,6. Indeed, observational studies revealed that most patients with HF and severe (≥ 3+) MR have functional (74%), rather than degenerative (21%), MR⁷. While surgery is the gold-standard therapy in patients with organic (i.e., degenerative) mitral valve disease associated with symptoms or evidence of left ventricle dysfunction⁸, its benefit to patients with MR secondary to underlying ventricular dysfunction (i.e., functional MR) remains unclear⁹. Therefore, individuals with functional MR are frequently referred to isolated clinical management, carrying poor long-term prognosis⁷.

Percutaneous mitral valve transcatheter therapies, such as direct and indirect annuloplasty, leaflet repairing devices, and valve replacement, have recently emerged as potential alternatives for patients with MR. Percutaneous edge-to-edge mitral valve repair with the MitraClip system (Abbott Vascular, Abbott Park, Illinois) exhibits the largest body of data available among transcatheter therapies for MR¹⁰. The procedure has consistently demonstrated to be safe, coupled with efficacious MR reduction, left ventricle reverse remodeling, and improvement in congestive HF symptoms and in the quality of life of patients with either functional or degenerative MR^11,12. In fact, MitraClip implantation has been approved for commercial use for many years in Europe, but, in the United States, the approval has been recently given. In Brazil, the system has been just approved by the Brazilian Health Surveillance Agency (Anvisa) and is expected to be available in the near future.

The only prospective, randomized, controlled trial comparing MitraClip therapy and conventional surgery mostly for patients with organic MR (i.e., EVEREST II trial) has shown that the percutaneous procedure had superior safety and similar improvement in clinical outcomes, although the latter led to more effective reduction in the magnitude of MR¹⁰. It is currently under intense investigation whether catheter-based therapies could be offered as a minimally invasive strategy also for patients with severe MR secondary to left ventricular dysfunction. Recently, non-randomized studies including high-risk patients with functional MR have confirmed excellent safety and efficacy profiles of MitraClip implantation in more complex clinical scenarios, thus contributing to refine the understanding on the role of this novel therapy in patients with different MR etiologies^13,14.

Minimally invasive catheter-based therapies aimed at correcting (or minimizing) functional MR represent a whole new and promising therapeutic strategy for patients with advanced HF¹⁵. Notwithstanding its potential, the novel treatment must be scrutinized in the context of studies specifically designed to evaluate its clinical value in improving short- and long-term clinical outcomes.