Response of normal aorta to endovascular grafting: a serial histopathological study

To examine the histological changes caused by the presence of the endovascular stented graft in the native aorta.

Case series. Twenty Western crossbred adult male sheep underwent endovascular placement of an infrarenal aortic stented graft, using the Bard aortic aneurysm repair device catheter delivery system (Bard Vascular Systems, Dovermill, Mass). Six self-expanding wire hooks at 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 angiography and intravascular ultrasonography to study the aorta and the graft. The aorta was explanted en bloc with the left renal artery, pressure perfused with a formalin gluteraldehyde solution, and then underwent histological examination with hematoxylin-eosin, trichrome, and elastic tissue staining.

Description of histological changes at various intervals after endovascular stented graft placement.

Significant histological findings include (1) complete incorporation of the grafts into the aortic wall, with a pseudointima of smooth muscle cells and collagen; (2) a foreign-body reaction around the graft; (3) an organized blood clot noted between the graft and the aortic wall, without evidence of recent blood flow through the perigraft space or the lumbar vessels; and (4) focal replacement by collagen of the inner one third to one half of the media at the proximal anchor sites.

There was good incorporation of the graft without evidence of pressure necrosis, bleeding around the graft, or flow in the occluded lumbar vessels.