The intraluminal
elastase perfusion model has been proven to be potentially effective in producing
abdominal aortic aneurysms (AAA) in rodents, yet has produced unpredictable results in larger animals. The purpose of this study was to explore different variations to an existing
elastase perfusion model in the dog in the hopes of producing a consistent AAA for endovascular graft validation. The
elastase perfusion canine model was modified as follows: (1) inflation of a balloon
catheter in the infrarenal aorta (IA) of 3 dogs following
elastase perfusion with doses of 2800 U for 40 min; (2) perfusion of the IA of 5 dogs with various
elastase doses ranging from 2800 U to 8400 U for 2 h; and (3) perfusion of the IA of 2 dogs with
elastase and
collagenase for 2 h. The dogs were sacrificed at 4, 7, and 29 weeks. Prior to sacrifice, the treated aortic segments were either examined in vivo by x-ray angiography or by ultrasonography to measure aneurysmal dilation. The aortas were examined macroscopically postmortem to assess the
luminal surface characteristics, and under light microscopy and scanning electron microscopy to reveal any pathological
injuries induced by the various treatments on the aortic wall. Perfusion of the aorta with 2800 U
elastase for 40 min followed by balloon
catheter inflation either immediately or 3 weeks after perfusion produced no dilation. Perfusion for 2 h with either
elastase alone or in combination with
collagenase showed an increased aortic diameter averaging 65.6+/-20.8%, with an irregular dilation of the aortic wall. Histological examination revealed partially digested elastic network of the intima, media, and adventitia, as well as a reduction in the number of smooth muscle cells. An intimal hyperplasic reaction was observed in some of the dogs. Located sparingly within the intima were extravasated erythrocytes associated with recent
hemorrhages, intramural thrombi in reorganization, and occasional necrotic lesions. The various modifications brought to the
elastase perfusion model failed to produced an aneurysmal dilation with enough expansion to make it a reliable model for endovascular graft validation.