Intraventricular flow dynamics and thrombosis risk with a left ventricular assist device using accelerated thrombosis modeling and stress-blended eddy simulation

Abstract

Thrombosis remains a significant complication in blood-contacting medical devices. Computational studies on flow dynamics within a left ventricular assist device (LVAD) supported left ventricle (LV) have been conducted, yet there is a lack of detailed models capable of comprehensive LV flow dynamics analysis to predict localized thrombus risk. This study aimed to address these gaps by employing a scale-resolving turbulence model combined with an accelerated thrombosis model for intraventricular flow disturbed by an LVAD. A patient-specific LV model of a post-VAD patient was implanted with a HeartMate3 cannula. A complete heart failure scenario with a 5 L/min LVAD outflow and rigid walls was developed. The blood turbulence field was modeled using a Stress-blended eddy simulation turbulence model. The accelerated thrombosis model involved three convection-diffusion equations to trace the non-activated platelets, activated platelets, and adenosine diphosphate. Results were compared with residence time, a simplified thrombosis index commonly used in the literature. Blood residence time peaked at 7.5 s along the cannula surface and exceeded 3.5 s around the aortic root and behind the mitral leaflets. Concurrently, the scaled activated platelet concentration reached its maximum value on the cannula surface toward the cannula outlet. The activation rates of platelets indicate a negligible activation, suggesting that thrombosis occurring in the LV of LVAD patients is primarily due to prolonged blood residence, leading to increased coagulation.