Review Question - QID 109221

A 70-year-old male immigrant from Asia is brought to the emergency room with complaints of palpitations and light-headedness for 1 hour. The patient was sitting in his chair watching television when he felt his heart racing and became dizzy. He was unable to stand up from his chair because of weakness and light-headedness. His past medical history is notable for mitral stenosis secondary to rheumatic fever as a child. On arrival to the emergency department, the patient's temperature is 99.7°F (37.6°C), blood pressure is 110/55 mmHg, pulse is 140/min, and respirations are 15/min. The patient appears comfortable but anxious. Electrocardiogram shows atrial fibrillation with rapid ventricular response. The patient is started on dofetilide. Which of the following would be expected in this patient’s cardiac action potential as a result of this drug?