QUANTIFICATION OF MITRAL AND TRICUSPID REGURGITATION USING JET CENTERLINE VELOCITIES - AN IN-VITRO STUDY OF JETS IN AN AMBIENT COUNTERFLOW

A method for quantifying mitral and tricuspid regurgitant volume that utilizes a measure of jet orifice velocity U-o-m/sec), a distal center line velocity (U-m-m/sec), and the intervening distance (X-cm) was rec ently developed; where jet flow rate (Q(cal)-L/min) is calculated as Q (cal)=(U(m)X)(2)/(26.46U(c)). This method, however, modeled the regurg itant jet as a free jet, whereas many atrial jets are counterflowing j ets because of jet opposing intra-atrial flow fields (counterflows). T his study concentrated on the feasibility of using the free jet quanti fication equation in the atrium where ambient flow fields may alter je t centerline velocities and reduce the accuracy of jet flow rate calcu lations. A 4-cm wide chamber was used to pump counterflows of 0, 4, an d 22 cm/sec against jets of 2.3, 4.8, and 6.4 m/sec originating from a 2-mm diameter orifice. For each counterflow-jet combination, jet cent erline velocities were measured using laser Doppler anemometry. For fr ee jets (no counterflow), flow rate was calculated with 98% mean accur acy. For all jets in counterflow, the calculation was less accurate as : (i) the ratio of jet orifice velocity to counterflow velocity decrea sed (U-o/U-c, where U-c is counterflow velocity), i.e., the counterflo w was relatively more intense, and (ii) centerline measurements were m ade further from the orifice. But although counterflow lowered jet cen terline velocities beneath free jet values, it did so only significant ly in the jet's distal portion (X/D > 16, i.e., > 16 orifice diameters from the origin of the jet). Thus, the initial portion (X/D < 16) of a jet in counterflow behaved essentially as a free jet. As a result, e ven. in significant counterflow, jet flow rate was calculated with > 9 3% accuracy and > 85% for jets typical of mitral and tricuspid regurgi tation, respectively. Counterflow Lowers jet centerline velocities ben eath equivalent free jet values. This effect, however, is most signifi cant in the distal portion of the jet. Therefore, regurgitant jets, al though not classically free because of systolic atrial inflow or jet-i nduced intra-atrial swirling flows, will decay in their initial portio ns as free jets and thus are candidates for quantification with the ce nterline technique.