A Whole Blood Thrombus Mimic: Constitutive Behavior Under Simple Shear

Deep vein thrombosis and pulmonary embolism affect 300,000-600,000 patients each year in the US. The progression from deep vein thrombus to pulmonary embolism occurs when blood clots, as a whole or partially, break off from the deep veins and eventually occlude the pulmonary arteries. Venous thromboembolism is the cause of up to 100,000 deaths per year in the US alone. To date, we dont fully understand this mechanical process among other reasons because in-vivo samples are difficult to obtain, highly heterogeneous, and their shapes are inappropriate for most mechanical tests. Toward overcoming these obstacles, we have set out to develop an in-vitro thrombus mimic and to test this mimic under large deformation simple shear. In addition to reporting on the mechanics of our mimics under simple shear, we explore the sensitivity of their mechanics to coagulation conditions and blood storage time, and compare three hyperelastic material models for their ability to fit our data. We found that thrombus mimics made from whole blood demonstrate strain-stiffening, a negative Poynting effect, and hysteresis when tested quasi-statically to 50% strain under simple shear. Additionally, we found that the stiffness of these mimics does not significantly vary with coagulation conditions or blood storage times. Of the three hyperelastic constitutive models that we tested, the Ogden model provided the best fits to both shear stress and normal stress. In conclusion, we developed a robust protocol to generate regularly-shaped, homogeneous thrombus mimics that lend themselves to simple shear testing under large deformation. Future studies will extend our model to include the effect of maturation and explore its fracture properties toward a better understanding of embolization.