You are answering a USMLE-style medical question. Question: A 75-year-old man becomes pulseless in the cardiac intensive care unit 48 hours after admission for ST-elevation myocardial infarction. His blood pressure is 50/20 mm Hg. The ECG monitor shows a tachycardic irregular rhythm with erratic undulations, but no discernible P waves or QRS complexes. During immediate advanced cardiac life support, two attempts at defibrillation are made, after which the patient is given 1 mg of IV epinephrine. After another attempt at defibrillation, the patient remains pulseless and his blood pressure is 60/35 mm Hg. The ECG monitor shows no changes. Administration of which of the following is the most appropriate next step in management? Options: A) Amiodarone B) Epinephrine C) Dopamine D) Atropine Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.