A model based on dimensional analysis for noninvasive quantification of valvular regurgitation under confined and impinging conditions: in vitro pulsatile flow validation.

A technique is proposed for the noninvasive quantification of regurgitant flows under confined and impinging conditions. Its use requires only the knowledge of the jet orifice velocity, receiving chamber diameter, orifice-to-end wall distance and any downstream jet centerline velocity at a known distance from the orifice. The technique is based on dimensional analysis and provides a prediction of peak regurgitant flow rates. To validate the technique, known physiologic pulsatile flows were pumped through 2- and 4-mm circular orifices at 70 to 150 beats/min, into two different receiving chambers of 51 and 88 mm in diameter. At each heart rate, the peak orifice velocity was varied from 2 to 5 m/s, and the orifice-to-end wall distance was varied from 30 to 93 mm. Centerline velocities were recorded by pulsed Doppler ultrasound and averaged over multiple beats. A dimensional analysis of the parameters of the study provided an equation relating normalized centerline velocity to orifice-to-end wall distance, chamber diameter and downstream location. Statistical modeling of the experimental data was performed to compute the constants involved in this equation. The estimated (i.e., predicted by the technique) peak regurgitant flow rates were found to fall within 10% of the actual values, when centerline velocities were measured over a range of centerline distances from six orifice diameters to 85% of the chamber length. Therefore, the proposed technique provides, for the first time, a quantitative method for calculating valvular regurgitant flow rates under confined and impinging conditions.