Flow-Induced Platelet Activation in Bileaflet and Monoleaflet Mechanical Heart Valves

Abstract

Abstract-A study was conducted to measure in vitro the procoagulant properties of platelets induced by flow through Carbomedics bileaflet and Bjork-Shiley monoleaflet mechanical heart valves (MHVs). Valves were mounted in a left ventricular assist device, and platelets were circulated through them under pulsatile flow. Platelet activation states (PAS) were measured during circulation using a modified prothrombinase method. Computational fluid dynamics (CFD) simulations of turbulent, transient, and nonNewtonian blood flow patterns generated by the two valve designs were done using the Wilcox k − ω turbulence model, and platelet shear-stress histories (the integral of shear-stress exposure with respect to time) through the two MHVs were calculated. PAS measurements indicated that the bileaflet MHV activated platelets at a rate more than twice that observed with the monoleaflet MHV. Turbulent flow patterns were evident in CFD simulations for both valves, and corroborated the PAS observations, showing that, for particles close to the leaflet(s), shear-stress exposure in the bileaflet MHV can be more than four times that in the monoleaflet valve.

The Syncardia™ total artificial heart: in vivo, in vitro, and computational modeling studies

“…5b). In comparison to other device components, i.e, the St. Jude Medical bileaflet mechanical heart valve (MHV) alone at 6 × 10 −4 min −1 (Yin et al, 2004; Yin et al, 2005) this is slightly higher PAR—as expected by the additional components of the TAH. Further, device performance and operating parameters play a significant role in overall thrombogenicity and need to be optimized based on patient-specific cardiac outputs and anticoagulation regimens.…”

“…The blood was centrifuged at 650 × g for 6 min to separate red blood cells from platelet rich plasma (PRP). Purified platelets in modified Tyrode’s buffer were prepared from PRP by gel filtration as previously described (Yin et al, 2004), diluted (2 × 10 7 /ml) and used for the in vitro flow-loop studies in the TAH described below. Timed samples were analyzed with a modified prothrombinase assay that measures the rate of thrombin generation in direct proportion to shear stress (Jesty and Bluestein, 1999).…”

“…5a), under two representative operating conditions: 95% ventricular filling at 100 min −1 (cardiac output=6.7 L/min) and at 130 min −1 (cardiac output =8.7 L/min). Platelets were sampled every 10 min for activation measurements as previously described (Yin et al, 2004; Yin et al, 2005). …”

Multiscale Particle-Based Modeling of Flowing Platelets in Blood Plasma Using Dissipative Particle Dynamics and Coarse Grained Molecular Dynamics

“…The coagulation cascade of blood may be initiated by flow-induced platelet activation, which prompts clot formation in prosthetic cardiovascular devices and arterial disease processes 5,9,75 . While platelet activation may be induced by biochemical agonists, high shear stresses arising from pathological flow patterns or cardiovascular devices enhance the propensity of platelets to activate and initiate coagulation pathway, leading to thrombosis 1,35,45,73 .…”

Lagrangian Postprocessing of Computational Hemodynamics

“…Bluestein et al [14, 13] have studied the vortex shedding phenomena behind MHVs, showing that platelets initially exposed to high shear get trapped in the formed vortices, consequently contributing to a higher AP level, similarly shown in [134]. Performance of bileaflet and monoleaflet MHVs have been compared showing higher AP levels for the bileaflet MHVs [158, 9]. The AP levels of different commercial bilieaflet MHVs has also been compared [39, 154, 160].…”