Atrial functional mitral regurgitation (MR) has been featured as the JACC Review Topic of the Week . Atrial functional MR is due to isolated mitral annular dilatation with insufficient leaflet growth and impaired annular dynamics. It occurs typically in atrial fibrillation and heart failure with preserved ejection fraction (HFpEF). It is different from MR secondary to left ventricular dysfunction. In left ventricular dysfunction, tethering of mitral leaflets is an important cause for mitral regurgitation while it is not so in atrial functional MR. Hence MR secondary to left ventricular dysfunction is usually an eccentric jet, whereas atrial functional MR produces a central jet as the leaflets fail to coapt in the centre. There is insufficient leaflet lengthening or remodeling to produce coaptation in the setting of annular dilatation .
Atrial functional MR can occur in 6-7% cases of lone atrial fibrillation. The prevalence is much higher in HFpEF (upto 53%). The severity of left atrial dilatation is much more in atrial functional MR when compared to MR secondary to left ventricular failure.