Histopathologic analysis of endovascular stent grafts from patients with aortic aneurysms: Does healing occur?

Background: Research with animal models has demonstrated tissue healing of endovascular grafts in both native arterial segments and in experimentally created arterial aneurysms. Fundamental to the successful clinical use of e ndovascular grafts for the treatment of aneurysmal disease is the creation of a permanent hemostatic seal between the graft ends and the arterial wall . Characteristics of this healing process in patients with aneurysmal disea se have not been fully studied. In this study, we analyzed the macroscopic and histopathologic changes of the arterial wall after endovascular repair of aortic aneurysms. Methods: Over a 7-year period, 313 patients were treated with endovascular grafts to exclude arterial aneurysms of the thoracic and abdominal aorta. O f these patients, 11 had their endovascular grafts recovered for analysis. Five graft specimens were recovered during subsequent open aortic surgery. Six grafts were recovered at autopsy after the death of the patient of caus es unrelated to the patient's endovascular graft. All specimens were fixed in formalin. Histologic analysis included light microscopy with hematoxylin and eosin and trichrome stains. Well-preserved specimens were selected aft er light microscopic examination and postfixed in 3% buffered glutaraldehyd e for electron microscopy. The aortas from autopsy specimens were removed e n bloc and fixed in formalin; representative regions of each graft were sec tioned for analysis. Adherence of the graft to the vessel wall was categori zed as densely adherent or easily separated after graft explantation. Tract ion applied to the graft-aortic anastomosis was equal to traction generated by suspending a standardized 2-kg weight. Infrarenal graft specimens were obtained with supraceliac aortic clamping, longitudinal aortotomy, and graf t sampling before endograft revision. Results: In eight patients, endograft fixation was found to be firmly adher ent to the arterial wall. A translucent film of fibrinous material was cons istently seen across the entire luminal surface of the endograft. Light and electron microscopy failed to demonstrate an endothelial layer or organize d pseudointima at the graft-artery interface. Conclusion: Despite suggestive experimental data regarding endograft healin g in animals, minimal graft incorporation was apparent in the stent grafts recovered in this study. A greater emphasis on the construction and mechani sm of fixation of endograft attachment systems mill be important for long-t erm device function.