A 58-year-old man with diabetes and hypertension presents with a 3-month history of claudication in the left calf. He reports pain after walking 200 metres that resolves with rest. On examination, the left dorsalis pedis and posterior tibial pulses are diminished. Ankle-brachial index (ABI) on the left is 0.68. He is already on aspirin 75 mg daily and atorvastatin 40 mg daily. What is the most appropriate next step in management?