What to do with functional mitral regurgitation: what do we really know and how can we find out?

Abstract

Managing heart failure patients with left ventricular dysfunctionassociated mitral regurgitation (functional mitral regurgitation or FMR) is challenging and requires a multidisciplinary approach. Optimal medical therapy (OMT) with vigilant outpatient surveillance, cardiac resynchronization therapy (CRT) and myocardial revascularization can all have positive impacts on quality of life, and perhaps even survival. Since as many as 30% of individuals with heart failure have moderate–severe mitral regurgitation (MR), it is mechanistically appealing to postulate that correcting MR, whether by surgery or transcatheter MitraClip therapy, should benefit these patients. However, data supporting FMR correction are largely observational. The current American College of Cardiology/American Heart Association (ACC/AHA) guidelines give mitral valve repair in patients with symptomatic severe left ventricular dysfunction a Class IIa (level of evidence C) recommendation [1]. The European Society of Cardiology (ESC) guidelines also cite limited data (level of evidence C) supporting mitral valve correction and give primarily Class IIa/b recommendations for the surgical correction of MR in the setting of left ventricle (LV) dysfunction with or without coronary artery disease and planned CABG [2]. MitraClip therapy, by virtue of its percutaneous delivery, may offer improved safety when compared with surgical mitral valve repair in patients with predominantly degenerative MR, but at the expense of far less effective MR reduction [3]. It is felt, however, that MitraClip therapy may be ideally suited for the treatment of higher- or extreme-surgical-risk FMR patients in whom other treatment options are limited. What then, does the accompanying report add to our understanding of applying surgery or MitraClip to patients with FMR? And how does it help us answer the question of ‘what to do with FMR?’ In this issue of the journal, Taramasso et al .[ 4] retrospectively describe the clinical characteristics, in-hospital and intermediate to long-term follow-up of two groups of patients undergoing correction of FMR. The first group consists of 91 patients undergoing surgical correction of FMR over the last 10 years, the second group comprises 52 patients undergoing MitraClip implantation during the last 3 years of the surgical experience. All patients had either moderate–severe or severe MR, were symptomatic despite medical therapy (the nature of which is not specified) and had ischaemic or idiopathic dilated cardiomyopathy (a very heterogenous group, in terms of outcome behaviour and competing risks). The decision to perform surgical correction vs MitraClip therapy was based on a ‘multimodality decisionmaking process’, which included the logistic EuroSCORE, as well as other less-quantifiable factors such as liver cirrhosis, neurological impairment and frailty. Patients had pre- and post-procedure echocardiography (non-core lab adjudicated) and were followed clinically for a variable amount of time (median 18 months for surgery and 8.5 months for MitraClip).