162 - Endothelialization of Prosthetic Vascular Grafts

Summary

Each year in the United States, over 100,000 patients will undergo lower-extremity arterial reconstruction for peripheral vascular disease, and an additional 400,000 patients will have a coronary artery bypass graft (CABG) (1). Conduits for arterial reconstruction or bypass may be separated into two broad categories: autologous and prosthetic. Autologous conduits are derived from the patient's own tissue and include saphenous vein grafts, arm vein grafts, and arterial grafts such as radial artery or hypogastric artery grafts. Prosthetic conduits include fabric or plastic grafts such as expanded polytetrafluoroethylene (ePTFE or Gore-Tex) and polyester or Dacron. Other prosthetic grafts are fabricated from denatured, cross-linked tissue such as human umbilical cord vein grafts.

Regardless of the prosthetic graft used, the clinical experience with small diameter (<6 mm) prosthetic arterial grafts has been poor. The surface of all prosthetic grafts is thrombogenic, and rapidly becomes covered with a fibrin coating or pseudointima (Figure 162.1). In humans, this surface remains thrombogenic and acellular for the lifetime of the conduit. These grafts are unable to tolerate low-flow conditions. In contrast, autologous conduits retain a viable endothelium that actively inhibits thrombosis, making such grafts suitable for the low-flow conditions associated with CABG procedures or long bypass grafts to small arteries. One solution to the prosthetic graft problem is to try to create and maintain a healthy autologous endothelial surface on prosthetic arterial grafts.

For the same reason, it is desirable to minimize injury to the existing endothelium when implanting autologous bypass grafts. If the endothelium is injured, highly thrombogenic subendothelial collagen is exposed to circulating blood, leading to platelet adhesion (2).