ESTIMATION OF MITRAL REGURGITATION WITH A HEMIELLIPTIC CURVE-FITTING ALGORITHM - IN-VITRO EXPERIMENTS WITH NATIVE MITRAL-VALVES

To date, studies on the mitral flow convergence method have used rigid , circular, or slit orifices to represent the regurgitant orifice. In this study, explanted porcine mitral valves, with the entire mitral ap paratus preserved, were mounted in an in vitro model to reproduce the three-dimensional regurgitant orifice geometry while permitting close control and measurement of the experimental conditions. This experimen tal setup permitted the evaluation of the hemispheric and hemielliptic formulas under realistic physiologic conditions. In this study, a hea rt rate of 70 beats/min was used with cardiac outputs between 1.5 and 6 L/min. Peak regurgitant flow rates ranged from 7 to 16 L/min (regurg itant jet velocities ranged from 2 to 5.5 m/sec); peak aortic flow rat es ranged from 9 to 30 L/min. Four native mitral valves were used for these studies for a total of 28 stages. Although the hemielliptic modi fication has previously shown success in vitro and computationally, it has not been used clinically because of difficulty imaging the flow c onvergence region in three orthogonal planes. A curve-fitting algorith m was developed to extract the hemielliptic dimensions from two standa rd ultrasound views by rotating the transducer 90 degrees. Improved ag reement was obtained between true and calculated flow rates by the hem ielliptic formula (y = 1.02 x + 0.29; r = 0.91) compared with the hemi spheric formula (y = 1.18 x-2.2; r = 0.66). This method provides accur ate results with a realistic three-dimensional regurgitant orifice geo metry and has the capability of being incorporated as a function key o n an ultrasound machine for clinical application.