A simplified method for determining regurgitant fraction by Doppler echocardiography in patients with aortic regurtitation

Objectives. This study attempted to develop and validate a simple method for calculating aortic regurgitant fraction by use of pulsed wave Doppler echocardiography. Background. Although several investigators have been able to determine aortic regurgitant fraction by Doppler echocardiography, the methods used require accurate determination of the cross-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 outflow tract and the mitral valve annulus in normal subjects. To verify this, we used Doppler echocardiography to measure the flow velocity integral of the left ventricular outflow tract and the mitral annulus in the apical view in 50 normal subjects (32 men, 18 women, mean age 34 years). Results. Close correlation (r = 0.95) was observed between the flow velocity integral (FVI) of the outflow tract (OT) and that of the mitral annulus (MA): FVI_MA/FVI_OT = 0.77. Because mitral flow equals aortic flow in normal subjects, the ratio of the cross-sectional area of the mitral annulus to that of the outflow tract was 1/0.77. In patients with aortic regurgitation, the regurgitant fraction (RF) = (Aortic flow - Mitral flow)/Aortic flow = 1 - Mitral flow/Aortic flow. Substituting 0.77 for the area component of flow, RF = 1 - (1/0.77) · (FVI_MA/FVI_OT). To evaluate the accuracy of this method, we compared the regurgitant fraction derived by Doppler echocardiography with that from catheterization findings in 20 patients with aortic regurgitation (an isolated lesion was found in 14). The regurgitant fraction by catheterization was the difference between total (angiographic) and forward (thermodilution) stroke volumes as a percent of total flow. Good correlation was observed between catheterization and Doppler regurgitant fraction (r = 0.88, SEE 9%, p < 0.01). Conclusions. Thus, regurgitant fraction can be estimated from Doppler echocardiography in patients with aortic regurgitation by a method that requires only measurements of the flow velocity integral from the mitral annulus and left ventricular outflow tract.