A 58-year-old man with a 10-year history of type 2 diabetes mellitus and hypertension presents for elective laparoscopic cholecystectomy. On pre-anesthetic evaluation, he reports occasional dyspnea on exertion and denies chest pain. Physical examination reveals a blood pressure of 148/92 mmHg. Which investigation is most appropriate to assess his perioperative cardiac risk before proceeding with anesthesia?