Percutaneous treatment of abdominal aortic aneurysm in a swine model: understanding the behavior of aortic aneurysm closure through a serial histopathological analysis.

Abstract

Previous studies used covered stent grafts to treat abdominal aortic aneurysms; however, such devices block flow into aortic side branches. We used uncovered stents with and without additional embolization coils to treat abdominal aortic aneurysm in a swine model and examined serial histological changes in the aneurysms over a 6-month period. We examined aneurysms in 9 control and 9 treated pigs (5 received stents alone and 4 received stents and coils). Aneurysms were surgically created with abdominal fascia. Three days later, we percutaneously placed a self-expandable uncovered stent across the aneurysm. Coils were implanted through the stent into the aneurysm lumen. An aortogram immediately after stent placement showed no significant change in aneurysm lumen; however, in pigs that had aortograms between 6 weeks and 6 months after treatment, the diameter decreased (28% to 65%) in 4 of 5 pigs, and 1 had no discernible aneurysm. Three treated pigs died, but only 1 from rupture. In contrast, 7 untreated aneurysms ruptured (2 pigs died of other causes). Histological examination revealed that the aneurysm lumen was reduced after treatment by collagen production. This healing process was accelerated in aneurysms treated with both stents and coils. In contrast, only limited amounts of new collagen were found in untreated, ruptured aneurysms. Instead, the fascia was disrupted and there was evidence of collagen degradation. We found that uncovered stents reduce the likelihood of aneurysm rupture in a swine model without blocking arterial branches. The presence of coils enhanced filling of the lumen by collagen.