A 74-year-old male presents to the cardiology clinic reporting lightheadedness, near fainting, fatigue, chest discomfort, and shortness of breath. He had a medical history of myocardial infarction a month ago, treated with right coronary artery stenting in a local hospital. His current symptoms started two days after his discharge from the hospital. His temperature is 99 °F (37.2 °C), heart rate is 36 beats/min, blood pressure is 88/58 mm Hg, respirations are 19 breaths/min, and oxygen saturation is 92% on room air. A cardiac event monitor, which the patient carries with him, has been showing consistent bradycardia with an average heart rate of 36 beats per minute. Of the following, which is most likely to treat his symptoms for long-term management?
