Natural history of autologous blood clot embolization in Swine

Previous studies of the natural history of embolized clots in dogs have demonstrated rapid lysis, presumably because the canine fibrinolytic system is very active. The fibrinolytic activity in swine, however, is similar to humans, and for this reason the pig was chosen for our study. The gluteal branches of the external iliac artery in nine domestic swine were embolized with either unmodified or modified (heat-formed, Amicar) autologous clot. In addition, three pigs were embolized with unmodified autologous clot to branches of the gastrosplenic artery. The lysis of clot emboli in both groups was followed by serial angiography at 48 hours and 14 days. Clot lysis as assessed by euglobulin lysis and plasmin generation was not activated by the experimental technique. Necropsy was performed on the animals in the second group. Partial or total obstruction of all arteries was present 48 hours after embolization and only 50% of arteries were recanalized at 14 days. At necropsy, organized partially occluding clot was demonstrated in the splenic artery of all 3 embolized swine. It is concluded that: 1) swine provide an excellent animal model for studying the natural history of arterial embolization; 2) Amicar or heat-formed clot shows no advantage over simple autologous clot in retarding intra-arterial clot lysis, and 3) simple autologous clot is an effective material for temporary intra-arterial occlusion.