1020-5 A Flow Convergence Method to Quantitate Regurgitant Flow with a Flail Mitral Valve Leaflet: Finite Element Modeling and Experimental Studies

The flow convergence (FC) method has yielded variable results for calculation of regurgitant flow (RF) rates in mitral regurgitation (MR) with a flail mitral valve leaflet (FMVL). Two effects have been postulated as causing errors in FMVL geometry: 1) near the regurgitant orifice (RO) the direction of flow is nearly 90° to the Doppler beam; and 2) left ventricular wall and MVL surface constraints may cause distortion of the assumed hemispherical shape of the FC region. For our finite element modeling study, we used a FMVL model traced from actual echocardiographic images (Fig. A), and simulated continuous flow with RO areas 0.25 and 1.0 cm2 at RF's of 2, 3, 4, 6, L/min. The isovelocity data (Fig. B) was then adjusted to simulate the angle effects of Doppler sampling from the apex yielding images similar to actual clinical studies (Fig. C). Near the FMVL, as simulated for color Doppler, velocities are underestimated and near the septal leaflet, the isovelocity shells are elongated in a direction towards the scanning origin. The experimental in vitro model had a ‘smile-shaped’ prolapse type orifice 30 mm2 in cross-sectional area and was studied under pulsatile flow conditions over flow rates for1.5–20L/min. With the ultrasound transducer placed at an angle to maximize the extension of the FC alias extension towards the transducer and by using high aliasing velocities so as to mandate correcting for an inlet constraining angle related to leaflet configuration, but not for chamber wall constraint, the correlation for predicting flow was r=0.97 over flows from 2–12 L/min. The required inlet angle correction could be verified from the relationship of the FC results with the prolapse anatomy and the actual flows but was not required when the flow rate was high enough to be measured outside, or proximal to, the inlet funnel; at which time no correction was necessary. Our studies provide rational and easily implemented approaches useful in adapting the FC method to prolapsed or flail leaflet geometries