Relation between three-dimensional geometry of the inflow tract to the orifice and the area, shape, and velocity of regurgitant color Doppler jets: an in vitro study. The relation between three-dimensional geometry of the inflow tract to the orifice and the area, shape, and velocity of regurgitant jets was studied in a pulsatile in vitro color Doppler flow model. A 2.5 MHz transducer connected to a diagnostic ultrasound machine was placed in a water tank facing pulsatile jets (duration, 0.5 second) obtained by a calibrated injector. Flow rate from 6 to 52 ml/sec were tested through a 5 mm diameter circular orifice. Four different three-dimensional inflow tract geometries were compared: (A) sharp-edged, (B) Venturi (funnel), (C) converging conical, and (D) diverging conical. Mean velocities of jets were measured by continuous-wave Doppler echocardiography. Driving pressures were also measured by means of a fluid-filled catheter. Two observers independently digitized contours of maximal color jet areas by computer system from two separate sets of experiments. Results are given as the mean values of the four measurements for each parameter. Jet areas were correlated to flow rate, with no difference from A through D. The shape (eccentricity) of jets was different between A and B (p less than 0.05), between B and D (p less than 0.01), and between C and D (p less than 0.01). The shape of jets was correlated with flow rate, continuous-wave velocity, and pressure gradient in B, C, and D but not in A. Measured pressure gradients and estimated gradients by continuous-wave Doppler echocardiography were similarly correlated from A through D. 