Left ventricular patient-specific fluid dynamics simulations for artificial mitral valve placement

Correct sizing and placement of mitral prostheses in transcatheter mitral valve implantation (TMVI) is critical: a subset of patients is at risk of left ventricular outflow tract (LVOT) obstruction. Functional Computed Tomography (CT) provides 3D data from which procedural computational simulations can be performed. In this study, a patient-specific model was developed to computationally investigate blood flow and pressure gradients resulting from left ventricular (LV) wall motion after transcatheter mitral valve deployment. The model geometry consists of two LV inner surfaces imaged at end-diastole and end-systole. These surfaces were segmented and triangular surface meshes were constructed. Finite element computational software (COMSOL Multiphysics, Burlington USA) was used to calculate the closest-point distance and direction from the endocardial surface at end-diastole to the surface at end-systole. From this positional information, regional wall velocities were determined. Computational fluid dynamics (CFD) simulations were then used to simulate blood flow in the LV during systole by applying a moving wall boundary condition that explicitly defined the wall velocity on the end-diastolic surface. Computed LVOT gradients were found to be affected by LVOT geometry, valve size and orientation. These simulations are able to provide a good understanding of the various mechanisms underlying LVOT obstruction.