A new theoretical model for noninvasive quantification of mitral regurgitation

The most common objective assessments of mitral regurgitation are limited by their invasive or semiquantitative nature. Recent attempts at correlation with jet size from Doppler flow maps have failed to produce a direct measure of regurgitant volume and are fundamentally limited by the dependence of jet dimensions on factors other than flow volume. The purpose of this paper was to develop an equation, based on the physics of turbulent regurgitant jets, for calculating regurgitant volume from quantities that can be measured by Doppler ultrasound. The result is an equation forw flow rate Q as a function of orifice velocity Uo, a downstream centerline velocity Um and the intervening distance chi: Q = pi U2m chi 2/160Uo. This equation can also be modified to obtain total regurgitant volume in clinical pulsatile flow. The assumptions made demand a free turbulent jet for which momentum is conserved, but should otherwise be physiologically applicable. The advantage of this technique compared to correlations with jet size are its theoretical justification and ability to quantify regurgitant volume directly.