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': 'In a patient with mitral stenosis, disappearance of Loud S1 is associated with all except \nSelect and explain. \nA. Calcified valve, B. Aortic regurgitation, C. Heart block, D. Mild mitral stenosis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: ANS. DConditions associated with dulling of SI (disappearance of loud SI) in patient with mitral stenosis:1. Calcified mitral valve2. Aortic regurgitation (AR)3. Mitral regurgitation (MR)Absence of presystolic accentuation in mitral stenosis:1. Atrial fibrillation2. Presence of MR3. Flabby left atrium4. Atrial septal defect (ASD)5. After surgery6. Junctional rhythm.', 'role': 'assistant'}]