This week’s edition of the Step 1 Question of the Week is about cardio physiology. See if you can answer the question and then watch the video to learn the correct answer as well as the rationales for each option.
A 54-year-old man presents with shortness of breath and a racing heartbeat. He has a history of poorly controlled hypertension. ECG reveals an irregularly irregular heartbeat with a pulse of 140 to 150/min. After several drugs fail to adequately slow his heart rate, he is started on a drug that inhibits the myocardial Na+/K+ pump, which slows his heart rate to 100/min.
Which of the following points on the graph best depicts the changed physiology following administration of the last drug the patient was most likely prescribed (solid lines indicate normal)?