Echocardiographic assessment of mitral regurgitation.

Mitral regurgitation (MR) is one of the most frequent indications for valve surgery in developed countries, and echocardiographic assessment is an essential tool to evaluate its etiologies, severity, and therapeutic indications. The mitral valve apparatus is a complex structure composed of several parts: apart from the mitral valve leaflets and annulus, it also includes the chordae tendineae, papillary muscles, and left ventricular (LV) wall. MR can be caused not only by organic changes of the mitral valve leaflets or chordae (primary MR) but also by extreme mitral annular enlargement or mitral leaflet tethering due to displacement and malfunction of papillary muscles and LV wall (secondary MR). In secondary MR with LV dysfunction, a milder degree of MR can be associated with adverse outcomes compared with primary MR. Grading the severity is the first step in evaluation of indication for surgical/transcatheter interventions. As such, there are several techniques to assess the severity of MR using echocardiography. However, none of the techniques is reliable enough by itself, and it is always recommended to integrate multiple methods. In cases where echocardiographic assessment of MR severity is inconclusive, magnetic resonance may be helpful. In addition to the severity, anatomical information, such as localization in primary MR due to mitral valve prolapse and LV size in secondary MR due to LV dilatation/dysfunction, is an important concern in presurgical echocardiography. Transesophageal echocardiography and three-dimensional echocardiography are key techniques for anatomical evaluation including mitral valve and LV volumes. In transcatheter intervention for MR, echocardiography plays a pivotal role as a guide for procedures and endpoints. In this review article, the authors provide a comprehensive summary of current standards of echocardiographic assessment of MR.