Mechanical Mechanisms for Thrombosis in Microvessels

The hypothesis that thrombus can be induced in curved vessels due to mechanical stimuli was tested both experimentally and computationally. Our in vivo experiments on the mesentery of Sprague-Dawley rats (250-300 g) showed that thrombi were formed in non-injured curved microvessels (post-capillary venules, 20-50 micrometer in diameter), and they were initiated at the inner side of the vessel. We observed thrombus formation in 7 out of 32 microvessels after they were stretched and curved for 10-60 mm. To investigate the mechanical mechanisms of thrombus induction, we performed 3-D computational simulation using commercial software, FLUENT. The blood flow was approximated as a Newtonian laminar flow with Reynolds number around 0.01 in this type of microvessels. We considered the vessels with different curvatures (90deg and 180deg) as well as different shaped-cross sections (circular and elliptic). Computational results demonstrated that the shear rate and shear rate gradient and at the inner side of the vessel were higher than those at the opposite side. The differences became larger in more bended and elliptic-shaped microvessels. This suggested that higher shear rate and shear rate gradient are two of the factors that initiate the thrombosis in curved post-capillary venules. Our results are consistent with others in branched venules