HISTOLOGICAL RESPONSE TO STENT GRAFT THERAPY

Background The purpose of the present study was to examine the histolo gical consequences of the endoluminal exclusion of blood flow effected with stent graft technology. Methods and Results In 25-kg mongrel dog s, patulous vein patch infrarenal aortoplasty with iliac vein produces a fusiform abdominal aortic dilation (AAD). All aortic tributaries we re preserved. Endoluminal exclusion via transfemoral placement of a th in-wall Dacron graft occurred 4+/-2 months later (n=23). Balloon-expan dable stents anchored the ends of the graft to the aorta. Hematoxylin and eosin, elastin van Gieson's, and Masson's trichrome staining was p erformed 6 and 12 months later at death. In control nongrafted AADs, t he arterial portion of the AAD was lined by elastin- and collagen-rich intimal hyperplasia, and the venous portion developed medial hyperpla sia containing collagen but little elastin. After stent graft placemen t, the stent struts and the graft were completely incorporated into an elastin-poor, collagen-rich neointima. Fibrosis of the vein patch was observed at 1 year. Laminated thrombus did not form in the AAD until immediately after stent graft placement; flow arrest occurred in the s pace between the graft and the AAD intima despite the patent tributari es. At 6 and 12 months, microscopic recanalization was seen in this th rombus, although macroscopic flow was not discernible by duplex imagin g or angiography. No AAD growth was measured. Conclusions Aortic dilat ion was not observed at 1 year after stent graft placement within AADs with patent side branches despite microscopic evidence of thrombus re canalization. A collagen-rich and elastin-poor neointima incorporated the entire stent graft.