Subsequent Intervention for Either Arm: Subsequent graft interventions will be determined by the clinical judgment of the patient's nephrologists, independently of the study intervention. Such intervention may include mechanical thrombectomy with angioplasty if the graft re-thromboses; referral for diagnostic fistulogram with possible angioplasty if there is clinical suspicion o graft stenosis; surgical revision if the graft has a stenosis that is not amenable to radiologic intervention; and placement of a dialysis catheter if graft patency cannot be restored. All these events will be tracked prospectively. Completeness of information about subsequent access interventions will be optimized by a cross-check with the Division of Nephrology prospective, computerized, access database maintained by our Access Coordinators [40].