regurgitant fraction

Regurgitant fraction answers a simple question: of all the blood a ventricle pushes out through a leaky valve in one beat, what proportion leaks straight back instead of going forward? It is given as a percentage, so a regurgitant fraction of 30% means roughly a third of the ejected blood washed backward.

It is a useful way to quantify how bad a leak is, because raw symptoms can be deceptive. The larger the fraction, the more wasted work each beat represents and the heavier the volume burden on the chambers handling the backflow. Broadly, a higher percentage corresponds to more severe regurgitation; in aortic and mitral regurgitation, values reaching roughly 50% or more typically indicate severe disease.

The fraction is calculated from echocardiographic or MRI measurements of total versus forward stroke volume — the difference being what leaked. Like all such estimates it depends on accurate measurements and assumptions, so it is interpreted together with other signs of severity such as chamber enlargement and the appearance of the regurgitant jet.

Quantitative severity grading combines several parameters; regurgitant fraction is one input among many in specialist assessment.