Functional Mitral Regurgitation and Transcatheter Mitral Annuloplasty

Abstract

In this issue, Schofer and colleagues present findings from the Carillon Mitral Annuloplasty Device European Union Study (AMADEUS), an uncontrolled multicenter trial in which percutaneous placement of a cinching device in the coronary sinus is used to treat functional mitral regurgitation (MR) of ischemic and nonischemic etiologies.1 Of 48 patients enrolled, the device was successfully implanted in 30. Major adverse events occurred in 6 (13%) of 46 patients based on intent-to-treat. The severity of MR, based on 4 echocardiography/Doppler measures, decreased between 22% and 32%. There was substantial functional improvement (assessed by New York Heart Association functional class, 6-minute walk test, and the Kansas City Cardiomyopathy Questionnaire) at 1-month and 6-month follow-up. The study is at once exciting and provocative; it is the extrapolation of its results to clinical practice that may be controversial. Article see p 326 Implications of Functional MR Functional MR occurs as a result of malcoaptation of anatomically normal mitral leaflets caused by restricted systolic motion in the setting of dilation and/or geometric distortion of the left ventricle (LV), with or without mitral annular dilation. Its causes and outcomes are inherently different from organic MR that occurs as a result of anatomic abnormalities of the mitral apparatus. Functional MR has been associated with an adverse prognosis among patients with dilated 2 and ischemic cardiomyopathy,3 with increased risks of heart failure and death. Surgical intervention has been associated with improved symptoms of heart failure and LV reverse remodeling.4,5 However, intervention for functional MR has not been shown to improve survival.6 The reasons for this may be complex, but possibilities include a true absence of survival benefit associated with intervention; inadequate reduction of MR or recurrence of MR with the use of existing techniques; or an inability to detect a potentially small survival benefit in patients with confounding risks of coronary artery disease and LV systolic dysfunction in studies limited to relatively few patients and relatively short follow-up duration. At present, the absence of data supporting mortality benefit leads to strong opinions but no consensus as to whether, and in whom, functional MR should be addressed.