Fluid mechanics of asymmetric regurgitant jets: Effect on color Doppler jet areas

Although current models of valvular regurgitation frequently assume central free jets, many regurgitant jets in patients are assymetric, do not originate from the center of the regurgitant valve, and occur into a confined chamber, either the left atrium or the left ventricle. To evaluate the effects jet assymetry and direction on color Doppler jet areas in a confined chamber, we studied 3 different types of jets using orifices of identical areas: a) symmetrical central; b) eccentric, directed towards an adjacent wall; and c) assymetric directed centrally. All orifices were studied in vitro in a pulse duplicator system simulating the mitral position at physiologic pressures and gradients using color Doppler flow imaging. As flow increased, jet areas initially increased in size and then progressively decreased. This effect was more pronounced with larger orifices. Eccentric jets directed toward adjacent walls were smallest in size (range 2.9 - 3.8 cm²) while eccentric jets originating near but directed away from the adjacent wall were largest for a given flow rate (range 7.8 - 8.9 cm²). Central, symmetric jets were intermediate in size. These findings demonstrate that jet areas do not increase monotonically with increasing flow and suggest that jet direction and symmetry are of lesser importance in determining color Doppler jet size than viscous energy losses near chamber walls.