According to the American Heart Association, 8 to 12 million Americans have peripheral arterial disease (PAD), a disease in which blood flow to the arms and legs is decreased. PAD is usually due to atherosclerosis, a hardening and blockage of the arteries by fatty deposits. Decreased blood flow reduces the oxygen supply to nearby tissues, causing pain that may become worse during exercise. As PAD progresses, patients become at risk for critical limb ischemia, which is characterized by chronic pain, nonhealing wounds, and gangrene that may require amputation. In some patients, surgery is needed to bypass the blocked artery and restore blood flow. This procedure involves using either a vein from the patient or a prosthetic graft to redirect blood flow. Although the best results are obtained with veins, prosthetic grafts must be used when suitable veins are not available. The most commonly used prosthetic graft material is expanded polytetrafluoroethylene (PTFE); however, these prosthetic grafts tend to become blocked by blood clots, which has prompted a search for ways to prevent these clots.