Vascular stent deployment in vein bypass grafts: Observations in an animal model

Background. An important cause of vein graft failure is anastomotic stenosis caused by myointimal hyperplasia. Intravascular stents may allow balloon dilation of these hyperplastic lesions, thereby increasing secondary graft patency. Methods. To evaluate intravascular stent deployment in vein grafts, we implanted 26 stents across the anastomotic sites of reversed vein grafts in 13 sheep. Stent deployment was evaluated immediately and at 3, 8, and 24 weeks by arteriography, light microscopy, and scanning electron microscopy. In a second animal cohort, stent-arterial wall contact after deployment was evaluated with intravascular ultrasonography (IVUS). Stents were imaged with IVUS after partial (n = 5) and complete (n = 5) expansion in 10 sheep carotid arteries. Results. Stents were deployed across vascular anastomoses without immediate thrombosis. Partial neointimal coverage occurred after 3 and 8 weeks, with complete coverage by 24 weeks. Complications included distal migration (n = 3), arteriographic stenosis (n = 2), and late graft occlusion (n = 2). Incomplete stent-vessel wall contact at deployment was observed in the stents with complications. IVUS accurately showed stent expansion and the degree of stent-vessel wall contact. Conclusions. Stents can be deployed in vein grafts with the expectation of neointimal coverage and maintenance of graft patency. IVUS may prove important in guiding optimal stent deployment by providing an assessment of stent-vessel wall contact