Development of a symmetric canine abdominal aortic aneurysm model with clinical relevance for endovascular graft studies.

This study was designed to develop a large-animal model to study and validate transluminally placed endovascular grafts and related techniques for treating abdominal aortic aneurysms with minimal trauma. In four dogs, a segment of infrarenal abdominal aorta was dissected and an endarterectomy was performed through an aortotomy to remove the entire intima of this controlled aortic segment. The opening was patched with chemically processed bovine pericardium, and an identical patch was applied after aortotomy of the opposite side of the aorta. Aortic diameter and flow were measured before and after the procedure. Angiograms were obtained just before retrieval. All dogs recovered quickly with no complications. Aortic diameter increased approximately 2.7-fold. Aneurysm size and shape remained stable until the end of the experiments at 4 or 8 weeks. Gross and histologic studies for 4- and 8-week specimens were similar. Factor VIII/von Willebrand factor staining showed complete reendothelialization of the endarterectomized wall, with a moderate degree of intimal hyperplasia. The patch material retained its acellular nature and its surface was covered with thrombus or fibrinous material mixed with blood cells and inflammatory cells. Thus, this model is feasible and suitable for endovascular graft healing studies.