Functional Mitral Valve Regurgitation, Pathophysiology, Leaflet ReModeling, and the Role of Imaging

Functional mitral regurgitation (FMR) is a complex left ventricle (LV) and left atrium (LA) disorder in which mitral valve regurgitation is just the "tip of the iceberg." Unlike primary mitral cvalve regurgitation, in which regurgitation occurs due to anatomic abnormalities of the valve itself, the etiology of FMR is multifactorial. Regional and global LV dysfunction, extent and location of fibrotic myocardium (subendocardial/transmural scar), and annulus enlargement are the leading causes of valve regurgitation. A comprehensive understanding of the causes, mechanisms, severity, and clinical consequences of FMVR relies primarily on noninvasive imaging techniques. Echocardiography is the first-line and most commonly used imaging technique. Cardiac magnetic resonance (CMR) has gained growing consensus mainly because it can precisely identify the extent and location of fibrotic myocardium. This review aims to: (a) describe the pathophysiology of the most common phenotypes of FMR, (b) challenge the paradigm that mitral leaflets are structurally normal in FMR, and (c) illustrate the critical role of both echocardiography and CMR in the comprehensive assessment of FMR.