Fluid dynamics and the thromboembolic reaction in mesenteric arterioles and venules.

In the mesentery of the anesthetized rabbit, the thromboembolic reaction after wall puncture lasts six times longer in arterioles than in venules, a difference that cannot be explained by fluid dynamic conditions before puncture. In the present study, it was investigated whether this difference in response between arterioles and venules results from a different degree of stenosis by the thrombus and/or a difference in velocity changes resulting in a different pressure drop over the thrombus. Arteriolar and venular mean red blood cell velocity and vessel diameter were measured before puncture and after this injury in the stenosed vessel segment and upstream. Thrombi with similar heights were formed in arterioles and venules and induced similar degrees of stenosis. A surface area reduction less than 55% induced only a small and similar decrease in volume flow (less than 10%) in arterioles and venules. Reduced velocity, a measure of wall shear rate, increased similarly in both vessel types for similar degrees of stenosis. In conclusion, changes in fluid dynamic factors, as induced by thrombus formation, cannot be held responsible for the difference in thromboembolic reaction between arterioles and venules.