Over a million coronary bypass procedures using human saphenous vein (HSV) are performed yearly worldwide. Nearly half of these grafts fail over a period of 12 to 18 months. This leads to significant patient morbidity and increased healthcare costs. The leading cause of graft failure is intimal hyperplasia. It is an incompletely understood process whereby the endothelial cells comprising the most inner lining of a blood vessel lose their normal properties. This leads to eventual narrowing and occlusion of the graft. Current techniques used to harvest and prepare HSV damage the endothelial cells and vessel wall. The hypothesis of this proposal is that optimizing these techniques will reduce injury to the vessel and improve graft patency. Our studies will use porcine saphenous vein (PSV), which has been shown to have similar physical and physiologic properties to HSV. We will examine three specific harvesting techniques used uniformly across surgical practice: high pressure distension to identify leaks, vessel marking with toxic dye from surgical marking pens for orientation, and storage in a non-physiologic solution. We will investigate the utility of an in-line pressure release valve fitted to PSV to determine whether this can reduce distension injury to the endothelium while also providing adequate pressure to identify leaks in the vessel. Furthermore, we suspect that use of surgical marking pens for vessel orientation is toxic to the endothelium secondary to conversion of isopropyl alcohol to acetone, a fixative. We will investigate the use of an alternative marking dye, an analog of erioglaucine, which has been shown preliminarily to be not only non- toxic, but also potentially protective of vascular endothelium. Finally, we will investigate the effect of commonly used storage solutions, many of which are highly acidic and non-physiologic, on endothelial function of PSV and HSV. We will investigate alternative solutions and we will attempt to identify a more physiologic solution for vein conduit storage. Subsequently, we will investigate the effect of optimal harvest techniques on the development of intimal hyperplasia using an in vivo porcine model of carotid artery interposition with PSV. These interventions, although simple, may decrease patient morbidity and healthcare costs associated with HSV graft failure. These studies will add to our understanding of intimal hyperplasia and vascular biology and potentially modify the standard of care for vein conduit preparation in cardiac and vascular surgery.
The leading cause of bypass failure is intimal hyperplasia. Failure of vein bypass grafts leads to heart attacks, deaths, limb loss and re-operations. The studies in this proposal will add to our understanding of vein graft failure and will modify the manner in which surgeons harvest and prepare vein grafts for cardiac and vascular surgery and prevent the failure of these grafts.