The dynamics of platelets in high residence time fluid elements in the left ventricle under LVAD support. A Numerical Hemodynamics Study of Lagrangian tracking in Intraventricular Flows.

Left Ventricular Assist Devices (LVAD) are auxiliary pumps that contribute to the pumping from failing left ventricle. As such, they provide life-sustaining treatment for end-stage HF. The most probable cause for mortality and morbidity is stroke associated with thrombosis. We study the potential for activation and aggregation of platelets within the left ventricle(LV) caused by altered hemodynamics, using Lagrangian tracking in a moving-wall ventricle flow simulation. A numerical model was created from patient-specific ventricle wall motion segmented from Cine-CT. Platelet-mimicking flow tracers were injected during mitral valve openings and tracked for over 15 cardiac cycles. Platelet trajectory statistics showed groups of platelets that stayed together for extremely long times, despite having their origins at several injection times. Platelets accumulate and stay, unmixed with other fluid elements until they leave the LV as a cohesive cluster. The extremely long residence time in the LV, together with the close proximity with other activated platelets, could identify the occurrence of LVAD-induced LV hemodynamics that cause the high risk of thrombosis.