MSFinals-5000

An 80-year-old man presents with a four-week history of increasing fatigue and palpitations on exertion. He has a medical history of myocardial infarction and biventricular heart failure and is currently taking ramipril 5mg, bisoprolol 5mg, aspirin 75 mg, and atorvastatin 80 mg. During examination, his heart rate is 98/min irregularly irregular, and his blood pressure is 172/85 mmHg. An ECG confirms the diagnosis of new atrial fibrillation. What medication should be avoided in this patient?