A 60-year-old man presents to the emergency department with chest pain described as retrosternal chest pressure radiating to the jaw. The symptoms started at rest and coming and going, but never lasting more than 15 minutes. He has a prior history of hypertension and smokes 1 pack/day. He is currently chest-pain free and on physical examination the blood pressure is 156/88 mmHg, pulse 88/min, and O2 saturation 98%. The heart and lung examination is normal.His ECG shows ST-segment depression in leads V1 to V4 that is new, and the first set of cardiac enzymes is negative. He is diagnosed with unstable angina pectoris, admitted to a monitored unit, and started on low molecular weight heparin, aspirin, nitroglycerin, and beta- adrenergic blockers. He continues to have ongoing chest pain symptoms. Which of the following is the most appropriate next step in management?