In vitro validation of a new approach for quantitating regurgitations using proximal isovelocity surface area

The present work has been, designed to validate the calculation of the effe ctive regurgitant orifice (ERO) area with the use of a new formula that tak es into account the velocity profile (V-r vs r) and that is insensitive to errors in the determination of the position. of the orifice. Assuming a hem ispheric model, ERO 2 pir(2) . V-r/V-o (with V-o = velocity at the orifice) and (V-o/V-r)(0.5) = (2 pi /ERO)(0.5) r. Thus, the slope of the correspond ing linear regression allows ERO to be calculated as: ERO = 2 pi /slope(2). This approach was tested in vitro in pulsatile conditions on circular, con ical, and slit-like orifices. The calculated ERO was compared with the actu al jet cross sectional area derived from the transverse velocity profile at the jet origin. For the purpose of comparison, the "classical" ERO was cal culated for all the configurations, angulations, and threshold velocities. The relationship between (V-o/V-r)(0.5) was linear (r > 0.98) over a wide r ange of velocities. The nonhemispheric components were found to modify the constant and not the slope. The mean variation of the calculated ERO was 6. 5%. The correlation between. the calculated and the actual ERO was very clo se (>0.97) with slope equal to 0.96 By comparison with the new method, the classical formula gave an underestimation of the ERO that dramatically incr eased when studying the flow closer to the orifice or in the case of error on the measurement of r. In conclusion, a method using velocity profiles in stead of isolated values improves the accuracy of the proximal isovelocity surface area (PISA) method for measuring the ERO.