This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'Which wall of hea is enlarged first in a patient with mitral stenosis \nSelect and explain. \nA. Right atrium, B. Left atrium, C. Right ventricle, D. Left ventricle', 'role': 'user'}, {'content': "Answer: B \nExplanation: * Rheumatic fever is the leading cause of mitral stenosis (MS). Other less common etiologies of obstruction to left ventricular inflow include: * congenital mitral valve stenosis, * cor triatriatum, * mitral annular calcification with extension onto the leaflets, * systemic lupus erythematosus, * rheumatoid ahritis, * left atrial myxoma, and * infective endocarditis with large vegetations. * Pure or predominant MS occurs in ~40% of all patients with rheumatic hea disease and a history of rheumatic fever. Mitral Stenosis Pathophysiology:- Ref:- Harrison'sTM Principles of Internal Medicine 20th edition; pg num:- 1813", 'role': 'assistant'}]