IN-VITRO EVALUATION OF FORWARD AND REVERSE VOLUMETRIC FLOW ACROSS A REGURGITANT AORTIC-VALVE USING DOPPLER POWER-WEIGHTED MEAN VELOCITIES

To determine the accuracy of using power-weighted mean velocities for quantitating volumetric flow across a cardiac valve, we equipped pulsa tile flow-tank systems with a 25 mm porcine or a 27 mm mechanical valv e with various sizes of regurgitant orifices. Forward and reverse volu metric flows were measured over a range of hemodynamic conditions usin g two insonating angles (0 and 45 degrees). Pulsed Doppler power-weigh ted mean velocity measurements were obtained simultaneously with elect romagnetic or ultrasonic transit-time probe measurements. For the porc ine valve, Doppler measurements correlated well with electromagnetic n ow measurements for all (r = 0.75 to 0.97, p < 0.05) except the smalle st (2.7 mm) orifice (r = 0.19). For the mechanical valve, power-weight ed mean velocity measurements correlated well with ultrasonic transit- time measurements for each hemodynamic condition defined by pulse rate , mean arterial pressure, and insonating angle (r = 0.93 to 0.99, p < 0.01), but equations varied unpredictably. Thus, although power-weight ed mean velocity volumetric now measurements correlate well with now p robe measurements, equations vary widely as hemodynamic conditions cha nge. Because of this variation, power-weighted mean velocity data are not useful for quantitation of volumetric now across a cardiac valve a t this time. Further investigation may show how different hemodynamic conditions affect power-weighted mean velocity measurements of volumet ric flow.