Impact of Torsion on Left Ventricular Flow Based on Echocardiography-Computational Fluid Dynamics Framework

Beyond systolic contraction and diastolic relaxation, torsional motion is an essential component of left ventricular (LV) dynamics, but its effect on LV hemodynamics is not fully understood. Building on previous work, rotation of short-axis sections is incorporated into the 3D reconstruction of the LV using 2D echocardiography images, which serve as input to the curvilinear immersed boundary framework for LV flow simulations. The reconstructed LV geometry is within 20% of the spatial coordinates of piezoelectric transducers implanted close to the LV endocardium, a technique known as sonomicrometry. The simulation results are validated against intracardiac flow velocity measured by Doppler ultrasound. To assess the impact of torsion, two simulations (one with torsion and one without) are compared. Global flow patterns are similar between the two cases, but time-averaged wall shear force increases by 12.6% during systole and drops by 4.9% during diastole when torsion is included. Torsion also reduces washout efficiency, as the volume of fluid with residence time under one cycle is 16.6% lower, while fluid staying 1–2 cycles increases by 3.7%. Viscous frictional energy loss decreases by 3.8% for LV with torsion.