Angioplasty Arm: All patients diagnosed with a thrombosed graft will undergo mechanical thrombectomy within 48 hours of diagnosis in conjunction with angioplasty of the underlying stenotic lesion. The grafts are initially accessed with a single needle at the arterial limb of the graft. A glide wire is passed up to the central vessels and the needle exchanged for a 6-French catheter sheath. Mechanical thrombectomy is achieved with a Trerotola device. A second 6-French sheath is placed in the venous limb of the graft, and a glide wire passed into the arterial circulation. A Fogarty balloon is passed through the wire beyond the arterial anastomosis and pulled back to dislodge the clot. An anterograde and retrograde angiogram of the graft is performed to assess patency and to look and grade the stenotic lesions. Lesions at the venous anastomosis with at least 50% stenosis are considered hemodynamically significant. An angioplasty balloon is placed and inflated at the level of the stenotic site.