RESPONSE OF NORMAL AORTA TO ENDOVASCULAR GRAFTING - A SERIAL HISTOPATHOLOGICAL STUDY

Objective: To examine the histological changes caused by the presence of the endovascular stented graft in the native aorta. Design and Inte rvention: Case series. Twenty Western crossbred adult male sheep under went endovascular placement of an infrarenal aortic stented graft, usi ng the Bard aortic aneurysm repair device catheter delivery system (Ba rd Vascular Systems, Dovermill, Mass). Six self-expanding wire hooks a t the proximal anchor allow fixation to the aorta. After 1 month (n=6) , 3 months (n=6), and 6 months (n=8), the animals underwent repeated a ngiography and intravascular ultrasonography to study the aorta and th e graft. The aorta was explanted en bloc with the left renal artery, p ressure perfused with a formalin gluteraldehyde solution, and then und erwent histological examination with hematoxylin-eosin, trichrome, and elastic tissue staining. Main Outcome Measures: Description of histol ogical changes at various intervals after endovascular stented graft p lacement. Results: Significant histological findings include (1) compl ete incorporation of the grafts into the aortic wall, with a pseudoint ima of smooth muscle cells and collagen; (2) a foreign-body reaction a round the graft; (3) an organized blood clot noted between the graft a nd the aortic wall, without evidence of recent blood flow through the perigraft space or the lumbar vessels; and (4) focal replacement by co llagen of the inner one third to one half of the media at the proximal anchor sites. Conclusion: There was good incorporation of the graft w ithout evidence of pressure necrosis, bleeding around the graft, or fl ow in the occluded lumbar vessels.