Peripheral artery disease

A 57-year-old man comes to the emergency department because of intermittent, severe leg pain in both his calves for 2 weeks. He has a history of untreated high blood pressure, diabetes, and high cholesterol. For the past 3 years, the pain started after walking three blocks and only going away upon resting. In the past 2 weeks, he has had the same pain at rest. His temperature is 36.5°C (97.7°F), pulse is 78/min, respirations are 17/min, and blood pressure is 160/89 mm Hg. Examination shows both calves are atrophied and there is a paucity of hair, but no swelling or discoloration. Additionally, his lower calves are cool to the touch and dusky in appearance. Doppler ultrasound shows perfusion to both feet, and with its assistance blood pressures of 35/20 mm Hg in the posterior tibial artery are obtained bilaterally. Which of the following is most appropriate next step in management?