Thrombosis and Thrombolysis in Crushed Arteries with or without Anastomosis: A New Microvascular Thrombosis Model

ABSTRACT

This study introduces a new rat thrombosis model in which a 2-mm segment of femoral artery is crushed by an impact load. Ninety-five femoral arteries were divided into five groups. The vessels in Groups 1 and 2 underwent only crush injuries with a 15-kg and 25-kg load, respectively. Group 3 vessels were not crushed, but did undergo vessel anastomosis by a standard microsurgical technique. The vessels in Groups 4 and 5 were crushed by a 25-kg load, and then divided and anastomosed. During the procedure, the vessel lumina were topically irrigated with saline (Group 4) or heparin solution (Group 5). Thrombosis and thrombolysis were evaluated at set time points up to 56 days after operation.

While all vessels in Groups 1 and 3 remained patent, the rate of occlusive thrombus formation in Group 2 significantly (p <0.001) dropped from 85 percent at day 1 to 11 percent at day 7. The intima and media in Groups 4 and 5 were severely disrupted and often occluded the lumen. Group 5 had a significantly (p <0.01 to <0.001) lower rate of occlusive thrombus formation (40 to 45 percent) at days 1 and 7 than Group 4 (90 percent). Histology in Groups 2, 4, and 5 at day 1 showed no intimal and almost no medial tissue left in the crushed area. The adventitia and remaining external elastic lamina were adherent to thrombus in the occluded vessels or covered by fibrin and platelet mesh in the patent vessels.

The results documented that spontaneous thrombolysis occurs in thrombosed arteries following crush injury alone, but not in thrombosed arteries after crush injury followed by suture anastomoses. The degree of disruption of the internal elastic lamina and the presence of sutures appear to contribute to occlusive thrombus formation following crush injury and anastomoses. Topical irrigation with heparin solution, at the concentration routinely used clinically, significantly reduces the thrombosis rate at the anastomosis site in crushed vessels, but does not promote thrombolysis.