This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Radiology
[{'content': 'What is the location of the atrial and ventricular pacemaker lead tips, respectively, in this patient? \nSelect and explain. \nA. Right atrium and right ventricle, B. Right atrium and extracardiac, C. Extracardiac and right ventricle, D. Both leads are extracardiac', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The atrial lead is appropriately positioned in the right atrium. The right ventricular lead tip lies outside of the confines of the hea. If it were placed in the right ventricle, it would overlie the hea. The atrial lead is appropriately positioned in the right atrium. The right ventricular lead tip lies outside of the confines of the hea.', 'role': 'assistant'}]