Incorporating Torsion Into 3D Geometric Reconstruction of Left-Ventricle From 2D Echocardiography and Its Impact on Hemodynamics.

In addition to systolic contraction and diastolic relaxation, torsional motion is an essential component of left ventricle (LV) wall motion, but its effect on LV hemodynamics is not fully understood. To this end, the measured rotation of short-axis sections is incorporated into our 3D reconstruction of LV from 2D echocardiography, which serves as input to the curvilinear immersed boundary framework for LV flow simulations. The geometry is validated against sonomicrometry measurements, whose difference is found to be within the typical myocardium thickness range, and the flow is validated against intracardiac flow velocity measured by Doppler ultrasound. To assess the impact of torsion, two simulations (one including torsion and one without in the reconstruction from the same set of images) are compared. It is found that including torsion in reconstruction for a normal LV does not change the geometry, and consequently the volume and flow rates, due to the circular shape of LV short-axis sections. However, the 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 for this subject, 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.