New Doppler techniques for the evaluation of regurgitant and shunt volumes

The aim of this review is to highlight some relatively new applications of Doppler echocardiography in children. Recent observations of flow dynamics through a restricted orifice have revealed that flow through an opening converges toward the orifice in a series of proximal isovelocity hemispheric surfaces. The flow convergence region can be demonstrated by Doppler echocardiography as a color mosaic on the ventricular side of the mitral valve in the presence of mitral regurgitation and on the left-ventricular side of a ventricular septal defect with left-to-right shunting. The continuity principle dictates that regurgitant flow rate can be calculated as the product of the hemispheric surface area of the flow convergence region and the velocity at that hemispheric surface. Using this principle, investigators have made quantitative flow measurements of mitral regurgitation, ventricular septal defect flow and aortic regurgitation. These studies demonstrate that this new technique of noninvasive quantification has the potential of providing direct measures of regurgitant and shunt flow. However, further validation in the pediatric population is needed before it can be incorporated into routine clinical practice.