This proposal will extend the novel clinical work of the BEST-CLI trial by studying the mechanisms of bypass vein graft and ... Adequate popliteal, tibial, or pedal revascularization target. *Willing to comply with protocol, attend follow-up appointments ... The investigators will adjudicate the mode of revascularization (vein graft or stent) in a central core laboratory, measure ... Presence of a femoral, popliteal or tibial aneurysm of the index limb ...