Mechanism of ischemic mitral regurgitation.

The basic mechanism of ischemic mitral regurgitation (MR) is believed augmented leaflet tethering due to the outward displacement of the papillary muscles by left ventricular (LV) remodeling or dilatation. Annular dilatation and LV dysfunction may not be the central mechanism, but contribute to the development of MR in the presence of augmented tethering. Papillary muscle dysfunction was initially expected to cause leaflet prolapse and MR. However, multiple studies have confirmed that papillary muscle dysfunction per se does not usually cause ischemic MR and recent studies further suggest that papillary muscle dysfunction may occasionally attenuate tethering and MR. Although surgical annuloplasty is usually effective to treat ischemic MR, occasional patients with persistent or recurrent ischemic MR after surgical ring annuloplasty even with advanced downsizing suggest the need for approaches to address tethering. Finally, leaflet tethering in patients with ischemic MR can be heterogeneous, indicating the need for individualized approaches to correct ischemic MR in affected patients.