An Image-Based Computational Fluid Dynamics Study of Mitral Regurgitation in Presence of Prolapse

Abstract

Purpose In this work we performed an imaged-based computational study of the systolic fluid dynamics in presence of mitral valve regurgitation (MVR). In particular, we compared healthy and different regurgitant scenarios with the aim of quantifying different hemodynamic quantities. Methods We performed computational fluid dynamic (CFD) simulations in the left ventricle, left atrium and aortic root, with a resistive immersed method, a turbulence model, and with imposed systolic wall motion reconstructed from Cine-MRI images, which allowed us to segment also the mitral valve. For the regurgitant scenarios we considered an increase of the heart rate and a dilation of the left ventricle. Results Our results highlighted that MVR gave rise to regurgitant jets through the mitral orifice impinging against the atrial walls and scratching against the mitral valve leading to high values of wall shear stresses (WSSs) with respect to the healthy case. Conclusion CFD with prescribed wall motion and immersed mitral valve revealed to be an effective tool to quantitatively describe hemodynamics in case of MVR and to compare different regurgitant scenarios. Our findings highlighted in particular the presence of transition to turbulence in the atrium and allowed us to quantify some important cardiac indices such as cardiac output and WSS.

Turbulence and blood washout in presence of mitral regurgitation: a computational fluid-dynamics study in the complete left heart

“…Then, for each reconstructed frame, we merged the geometry of LV with the AR and LA ones in MeshMixer (https://www.meshmixer.com to obtain the final surface mesh of LH, see Figure 1, step C. Subsequently, we registered the displacement of each frame with respect to the end systolic configuration by exploiting the non-affine B-splines algorithm implemented in the Elastix open source library (http://elastix.isi.uu.nl) [42] used and validated in [35]. The output is the surface mesh of LH at the end systolic instant, where the displacement field , is defined for all the 30 frames.…”

“…The entire procedure is reported in Figure 1, from step D to E. Regarding the MV reconstruction, starting from the Rotated series of MV, we reconstructed its shape in the fully closed (FC) and fully open (FO) configurations by using the method proposed in [38] (see step D in Figure 1), where the authors performed structural analysis, see also [43]. This method is based on tracing the valve leaflets in each plane to obtain a 3D point cloud that was after fitted with a B-Spline and then turned into a surface mesh of triangles in Matlab (www.mathworks.com), see [35] for details, where this MV reconstruction procedure has been, for the first time, applied to DIB-CFD simulations.…”

“…To treat the presence of the valves, we used the Resistive Immersed Implicit Surface (RIIS) method [47,48] and to evaluate the transition to turbulence, we employed the σ-LES method proposed for ventricular blood dynamics [49] and successfully used in different hemodynamic applications [50,51]. The entire method is described in a previous study [35]. In particular, the displacement of LH is used to compute the wall velocity to prescribe as boundary condition for the NS equations.…”

“…Heart rate The acquisitions were performed with the Achieva 1.5T (TX) -DS (Philips, Amsterdam, Netherlands) technology. Specifically, for each patient, we have at disposal different acquisitions: the Short Axis series of LV, the Long Axis series and the Rotated series of MV (see [35] for further details). Moreover, for subject H we have at disposal also the Short Axis series of AR, consisting in volumetric series made of 4 slices with thickness and distancing of 8 mm along the aortic root main axis, with a spatial resolution of 1 mm and time resolution equal to 30 frames/cardiac cycle; see Figure 1, left.…”

“…The latter approach has become, in the last decade, a valid alternative to FSI models when sufficiently detailed dynamic medical images are available [25][26][27][28][29][30][31][32]. In particular, regarding MVR, we mention works where the authors tested and compared different types of mitral valve prolapse [33], different degrees of MVR [34] and different functional changes of the ventricle and atrium in response to MVR [35]. However, no one of these studies was performed on a fully patient-specific LH geometry and displacement (ventricle + atrium + mitral valve + aortic valve + aortic root).…”