AKT-0349

A 72-year-old man presents with palpitations and feeling dizzy. An ECG reveals atrial fibrillation with a heart rate of 130 beats per minute. His blood pressure is within normal limits and there are no other notable findings upon examination of his cardiorespiratory system. He has a medical history of controlled asthma (treated with salbutamol and beclomethasone) and depression (managed with citalopram). He has been experiencing these symptoms for approximately three days. What is the most suitable medication for controlling his heart rate?