A new disease entity: Atrial functional mitral regurgitation.

Functional mitral regurgitation (MR) has been traditionally known as secondary MR resulting from left ventricular (LV) dilatation and systolic dysfunction. However, deterioration of functional MR also relates to mitral annular (MA) dilatation. Furthermore, MA dilatation due to left atrial dilatation in patients with atrial fibrillation (AF) can also cause functional MR, even in the absence of LV systolic dysfunction, in a condition referred to as "atrial functional MR" (AFMR). AFMR also has other etiological factors, including disruption of the MA saddle shape, reduction in MA contractility, inadequate compensation for the MA dilatation resulting from the lack of leaflet remodeling, and hamstringing of the posterior mitral leaflet by atriogenic tethering. AFMR has recently received much attention as an important cause of heart failure, and it represents a considerable therapeutic target in heart failure patients with AF. The traditional functional MR occurring in patients with LV dilatation and systolic dysfunction has since been designated "ventricular functional MR" (VFMR) to distinguish it from AFMR. This review article compares the current perceptions of newly recognized AFMR with those of traditional VFMR.