Inhibition of neointimal formation and hyperplasia in vein grafts by external stent/sheath

Abstract

Synthetic and to a lesser extent vein graft failure is still a major problem in the treatment of peripheral arterial disease, with neointimal hyperplasia being the main cause for graft occlusion in the medium and long term. This review aims to establish the current status of external stents or sheaths in the prevention of intimal hyperplasia in small diameter (< 6 mm) vein grafts.

Collagen External Scaffolds Mitigate Intimal Hyperplasia and Improve Remodeling of Vein Grafts in a Rabbit Arteriovenous Graft Model

“…However, the efficacies of those treatments have not been confirmed yet [4, 7, 9]. Accumulating evidence shows that the external scaffold is an effective surgical intervention to inhibit IH of vein graft in multiple experimental and clinical researches [10, 11]. Study on biodegradable stent brings a new direction for our research.…”

Inhibition of vein graft remodeling and neo-intimal formation using a cobalt chrome external support

“…External support targets some of the key factors associated with the development of intimal hyperplasia such as high circumferential wall stress and disturbed flow patterns due to luminal irregularities. Mildly constricting the vein grafts with a mechanical support reduces the wall tension induced by the arterial pressures and prevents the non-uniform dilatation of the graft post implantation period [6,7]. Meirson et al have shown that external support led to improved lumen uniformity of saphenous vein grafts 12 months post-implantation which was directly correlated with a significant reduction in oscillatory shear stress and the development of intimal hyperplasia [8].…”

“…Most of the pharmacological therapeutic modalities have shown a limited effect in the clinical setting [2,5]. Recently, external mechanical supports have shown considerable promise in pre-clinical testing with significant mitigation of proliferative intimal hyperplasia achieved by reducing wall tension, improving lumen uniformity and creating a protective "neo-adventitia" layer, rich with microvasculature [6,7]. In the clinical setting, the same biological effects were observed in externally stented saphenous vein grafts twelve months after coronary artery bypass grafting (CABG) [8][9][10].…”

“…The carotid artery interposition grafting model chosen for this study is commonly used for studying peripheral bypass [6] and assessment of vein disease development. The model allows the superficial position of the test article, without violating a major body cavity and enables monitoring with duplex ultrasonography.…”

External support in preventing vein graft failure

“…19,21 Following the progression of a noninfectious ''peri-vasculitis'' induced by external biomaterials, a more pronounced deposition of fibroblasts, VSMC, and extracellular matrix would occur in the outer rather than the inner layers of the venous wall, and thus a significant loss of intraluminal area could be prevented. 8,13 Inhibiting the progression of atherogenesis Emerging evidence has clearly shown that superimposed atherosclerosis is responsible for late vein graft failure after CABG. 2 It is noteworthy that external supports profoundly improve the atherosclerotic resistance of veins by prompting the expression of several antiatherosclerotic mediators such as NO, prostacyclin I 2 , cyclic adenosine monophosphate, and cyclic guanosine monophosphate; 22 and by inhibiting biofactors that are essential for atherogenesis, including a significant reduction of cholesterol and lipid content, as well as a lower expression of VCAM-1 and PDGF in the intima and media of the venous wall.…”