[Functional mitral insufficiency].

Abstract

The term "functional mitral regurgitation" is generally used to indicate the presence of mitral regurgitation in patients with left ventricular systolic dysfunction in the absence of structural abnormalities of mitral leaflets and chordal or papillary muscle rupture. Functional mitral regurgitation is commonly found in heart failure, and its presence and severity seem to contribute to exercise intolerance and poor prognosis observed in heart failure patients. Several pathogenetic mechanisms have been proposed to explain the pathophysiology of functional mitral regurgitation, in particular a) mitral annular dilation, b) geometric changes in the left ventricle from a typical ellipsoidal shape to a more spherical shape, with apical and outward displacement of papillary muscles and restriction of valve motion ("leaflet tethering hypothesis"), and c) reduction of closing force of the mitral valve ("leaflet closing force hypothesis"), as a consequence of a lower difference between left ventricular systolic pressure (reduced from left ventricular dysfunction) and left atrial pressure (increased). The relative contribution of these mechanisms to the appearance of mitral regurgitation and its severity may differ in the single patient, depending on the extent of left ventricular geometric changes and degree of systolic dysfunction. The Doppler echocardiographic examination plays an important role in assessing the presence and hemodynamic relevance of functional mitral regurgitation, allowing both a semiquantitative (color Doppler flow imaging) and a quantitative approach (PISA, regurgitant volume and fraction by Doppler). Furthermore, echocardiography may contribute to clarify the pathophysiology of mitral incompetence and to evaluate the effects of treatment, pharmacological or surgical, currently available.