Studies have previously shown that the patency of vascular grafts can be improved by bonding heparin bonding to the surface of a graft material. For example in surgical bypass a Dacron graft bonded with heparin outperformed a conventional PTFE graft in terms of patency and clinical outcomes. Endovascular stent grafting with heparin bonded PTFE has also been shown to be superior to PTFE alone with a primary patency of 86.4% vs 79.9% in femoropopliteal disease. A recent trial has demonstrated impressive patency of 73% in long segment femoropopliteal disease (TASC C and D lesions) using a self expanding version of the heparin bonded, covered, Viabahn stent graft. Heparin bonded stent grafts have shown promise in preserving patency of other vessels. A pilot study demonstrating the safety of using the Viabahn Bx in FEVAR will support the rationale for larger studies of this question including randomization between conventional and heparin bonded stent grafts.