A comparative experimental study of the organization of arterial and venous thrombi.

Organization of a venous thrombus proceeds much faster than that of an arterial thrombus. Two different double-ligation procedures were used for study of the time sequence of thrombus organization by the vascularized (in situ) and devascularized (dissected) walls of the external jugular vein and common carotid artery in 21 mongrel dogs. Blood in the ligated segments of the in situ veins remained mostly fluid. In these segments, intimal hyperplasia was observed after 4 weeks with apparent preservation of an endothelial lining. However, in the dissected veins, the trapped blood rapidly thrombosed. Remarkable cell proliferation quickly occurred in these dissected walls with rapid invasion of the thrombus to achieve complete organization by 4 weeks. In contrast, a thrombus formed in the ligated segments of all arteries, whether in situ or dissected, and organization was much slower, requiring about 4 months for completion. Full-wall viability was maintained in 100% of the in situ veins and in 95% of the devascularized veins, but inner wall viability was lost in 30% of the in situ arteries and in 95% of the devascularized arteries.