Mitral regurgitation in cardiac resynchronization: solving another piece of the puzzle.

Cardiac resynchronization (CRT) has emerged as a highly beneficial alternative to patients with heart failure (HF), providing symptomatic improvement, reversing remodeling, and reducing mortality rates.1,2 Mitral regurgitation (MR) is an important pathological feature in cardiomyopathy, occurring in a fair proportion of patients with advanced HF and probably inducing additional adverse ventricular remodeling through volume overload.3 Thus, MR may be an important factor influencing the final benefits a patient receives after CRT. Early reports of the effects of CRT on MR were mixed, with a majority of reports suggesting a reduction in MR after CRT.4 In this emerging tale, the missing narrative was a thoughtful investigation of how CRT may influence MR. Such insights would help us to better understand the evolution of MR after CRT and potentially suggest means of optimizing MR reduction after CRT. Hence, the work by Solis et al5 examining the potential mechanisms underlying the improvement of MR after CRT is highly instructive. This group of investigators is best positioned to tease out the intricacies of the anatomic and functional factors influencing post-CRT MR, having done pioneering work in animal and clinical models of MR over the last decade, using 2D and 3D echocardiography. Their work has resulted in paradigmshifting insights into mechanisms of MR in various etiologic settings.6