A SIMPLIFIED METHOD FOR DETERMINING REGURGITANT FRACTION BY DOPPLER-ECHOCARDIOGRAPHY IN PATIENTS WITH AORTIC REGURGITATION

Objectives. This study attempted to develop and validate a simple meth od for calculating aortic regurgitant fraction by use of pulsed wave D oppler echocardiography. Background. Although several investigators ha ve been able to determine aortic regurgitant fraction by Doppler echoc ardiography, the methods used require accurate determination of the cr oss-sectional areas of intracardiac sites at which the volumetric flow is calculated. Methods. Our concept was based on a constant relation that exists between the cross sectional area of the left ventricular o utflow tract and the mitral valve annulus in normal subjects. To verif y this, we used Doppler echocardiography to measure the how velocity i ntegral of the left ventricular outflow tract and the mitral annulus i n the apical view in 50 normal subjects (32 men, 18 women, mean age 34 years). Results. Close correlation (r = 0.95) was observed between th e how velocity integral (FVI) of the outflow tract (OT) and that of th e mitral annulus (MA): FVIMA/FVIOT = 0.77. Because mitral flow equals aortic how in normal subjects, the ratio of the cross sectional area o f the mitral annulus to that of the outflow tract was 1/0.77. In patie nts with aortic regurgitation, the regurgitant fraction (RF) = (Aortic flow - Mitral flow)/Aortic how = 1 - Mitral flow/Aortic flow. Substit uting 0.77 for the area component of how, RF = 1 - (1/0.77) (FVIMA/FVI OT). To evaluate the accuracy of this method, we compared the regurgit ant fraction derived by Doppler echocardiography with that from cathet erization findings in 20 patients with aortic regurgitation (an isolat ed lesion was found in 14). The regurgitant fraction by catheterizatio n was the difference between total (angiographic) and forward (thermod ilution) stroke volumes as a percent of total flow. Good correlation w as observed between catheterization and Doppler regurgitant fraction ( r = 0.88, SEE 9%, p < 0.01). Conclusions. Thus, regurgitant fraction c an be estimated from Doppler echocardiography in patients,vith aortic regurgitation by a method that requires only measurements of the flow velocity integral from the mitral annulus and left ventricular outflow tract.