A Three-Dimensional Computational Fluid Dynamics Model of Regurgitant Mitral Valve Flow: Validation Against In Vitro Standards and 3D Color Doppler Methods

Abstract

3D color Doppler echocardiography has recently been employed to evaluate 3D proximal isovelocity surface area (PISA) and vena contracta (VC) area measures of regurgitant valve severity. Computational fluid dynamics (CFD) modeling may provide insight into the strengths and limitations of emerging 3D color Doppler applications for the quantification of mitral regurgitation (MR). The objective of this study is to evaluate a recently developed CFD simulation of regurgitant mitral jets under tailored hemodynamic conditions. Moderate MR (30 mL/beat) and severe MR (70 mL/beat) were simulated using an in vitro flow loop with an imaging chamber configured to model a regurgitant mitral orifice. A novel application of a 3D CFD model based on a finite element method approximation of the Navier–Stokes equation was used to simulate the regurgitant flow conditions. The CFD derived peak transorifice pressure gradient and velocity were compared against in vitro measurement standards. CFD simulation of proximal regurgitant flow events were compared against 2D and 3D color Doppler PISA and VC measurements. Compared to an in-line flow meter reference, the CFD model provided an accurate estimate of peak transorifice flow velocity (mean 459 vs. 442 m/s, respectively; relative error 5.7%). Compared to high-fidelity pressure transducers, the CFD model provided accurate estimates of peak transorifice pressure gradient (mean 90 vs. 85 mmHg, respectively; relative error 10.4%). Compared to 3D color Doppler PISA measures, the CFD model of isovelocity surface area was larger (relative difference 7–23%). The error was greatest for higher flow conditions. When compared to the actual orifice area, the 3D Doppler VC area was larger (3–14% relative error), whereas the CFD VC area was smaller (8–9% relative error) and more consistent with the expected reduction in area due to transvalvular flow compression. 3D CFD simulations of complex intracardiac flow events are accurate when compared to in vitro pressure and flow measures and are consistent with recently introduced 3D echocardiographic flow quantification methods. Future studies may employ validated CFD models to assess the strengths and limitations of emerging 3D color Doppler applications.