The following are multiple choice questions (with answers) about medical knowledge.   **Question:** A 55-year-old male presents to the emergency department with dyspnea and palpitations. He does not smoke cigarettes or consume alcohol, and past medical history is insignificant. Blood pressure is 115/75 mmHG and heart rate is 125/min. Heart rhythm is irregularly irregular. After initial treatment with IV digoxin the patient's heart rate drops to 85/min and remains irregular. Which of the following best explains the effect of digoxin in this patient?   (A) Blockade of beta-adrenergic receptors   (B) Calcium channel blockade   (C) Vagal stimulation   (D) Increased ventricular contractility
['(C) Vagal stimulation <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Blockade of beta-adrenergic receptors \n (B) Calcium channel blockade \n (C) Vagal stimulation \n (D) Increased ventricular contractility <> possible answers', "  A 55-year-old male presents to the emergency department with dyspnea and palpitations. He does not smoke cigarettes or consume alcohol, and past medical history is insignificant. Blood pressure is 115/75 mmHG and heart rate is 125/min. Heart rhythm is irregularly irregular. After initial treatment with IV digoxin the patient's heart rate drops to 85/min and remains irregular. Which of the following best explains the effect of digoxin in this patient? <> context@"]