EXTERNAL STENTING REDUCES LONG-TERM MEDIAL AND NEOINTIMAL THICKENING AND PLATELET-DERIVED GROWTH-FACTOR EXPRESSION IN A PIG MODEL OF ARTERIOVENOUS BYPASS-GRAFTING

Bypass of stenotic coronary arteries with autologous saphenous vein is an established treatment for ischemic heart disease. However, its lon g-term clinical success is limited(1,2). Late vein graft failure is th e result of medial and intimal thickening consequent upon medial vascu lar smooth muscle cell migration, proliferation and extracellular matr ix deposition, followed later by superimposed atherosclerosis(3). Thes e changes directly compromise graft blood flow and provoke thrombosis. Vein graft wall thickening may represent an adaptation imposed by art erial hemodynamic factors(4-6), and these factors have been shown to p romote vascular smooth muscle cell migration and proliferation through activation of key mediators including platelet-derived growth factor (PDGF)(7). Many pharmacological interventions aimed at preventing thes e long-term changes have proven unsuccessful in clinical evaluation(8) . We recently demonstrated in a pig saphenous vein graft model that ap plication of an external polyester stent to the outside of carotid int erposition vein grafts reduced intimal hyperplasia and total wall thic kness 1 month after implantation(9). However, it is not known whether the benefits of the stent are maintained in the longer term or what me chanisms underlie its effect. The present study therefore compared mor phological changes and PDGF expression in stented grafts and contralat eral unstented grafts in the same pigs, 6 months after graft implantat ion. Reduced medial thickening, neointima formation, and cell prolifer ation were sustained in externally stented grafts, and these effects w ere associated with a significant reduction in PDGF expression.