A 54 year-old woman presents to your cardiology clinic complaining of weakness, fatigue, palpitations and lightheadedness to the point of passing out while having dinner. Her medical history is significant for congestive heart failure and she was started on a new medication two weeks ago to improve her shortness of breath. On physical examination she has muscle weakness and depressed deep tendon reflexes. Laboratory tests revealed a potassium level of 6.4 mEq/Liter. ECG showed tall, peaked t-waves with loss of some p waves. Which of the following medications was this patient most likely given?
