A 68-year-old man presents with a one-year history of progressively worsening bilateral calf pain on exertion. The pain initially occurred after walking four blocks but now begins after less than one block. It is consistently relieved by 2-3 minutes of rest. He also reports a small, non-healing sore on his left great toe that has been present for three weeks. His medical history is significant for type 2 diabetes mellitus, hypertension, and hyperlipidemia. He is currently on metformin, lisinopril, and atorvastatin. He has a 45-pack-year smoking history.