- Be scheduled to undergo infra-inguinal bypass grafting surgery using excised autogenous vein for Chronic Critical Limb Ischemia (i.e., rest pain, non-healing ulceration or gangrene). For patients presenting with rest pain as the only manifestation of CCLI, must have the diagnosis confirmed by at least one of the following,: i.) an ankle pressure of < 50 mmHg (or ABI <0.4), ii.) a toe pressure < 30 mmHg, iii.) a reduced TCPO2 < 30 mmHg, or iv.) a severely ischemic or flat line transtarsal pulse volume recording (i.e., Category V).