This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'A 75 year old man who had been on bed rest for the past 14 days, complains of breathlessness and chest pain. The chest X-ray is normal. The next investigation should be: \nSelect and explain. \nA. Lung ventilation-perfusion scan, B. Pulmonary aeriography, C. Pulmonary venous angiography, D. Echocardiography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: This patient might be having pulmonary embolism, for which Pulmonary aeriography is diagnostic. Actually Chest CT with contrast has viually replaced invasive pulmonary angiography as a diagnostic test. Lung scanning has become a second-line diagnostic test for PE, used mostly for patients who cannot tolerate intravenous contrast. Echocardiography is not a reliable diagnostic imaging tool for acute PE because most patients with PE have normal echocardiograms. Ref: Harrisons principles of internal medicine, 18th edition, chapter 262.', 'role': 'assistant'}]