A 78-year-old man presents with a four-month history of intermittent dizziness, lightheadedness, and profound fatigue. Last week, he experienced an episode of near-syncope while sitting and watching television. He also reports occasional palpitations, which he describes as a “fluttering” in his chest followed by a long pause and a “thump”.

His past medical history is significant for hypertension, which is well-controlled. He has no history of coronary artery disease, heart failure, or thyroid disorders. His medications include lisinopril and atorvastatin. He has no known drug allergies. He is a retired accountant who quit smoking 20 years ago and consumes one glass of wine with dinner most evenings. His family history is noncontributory for premature cardiac disease.