This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmia 3, Subject name: Medicine
[{'content': 'Atrial fibrillation may occur in all the following conditions, except? \nSelect and explain. \nA. Mitral stenosis, B. Hypothyroidism, C. Dilated cardiomyopathy, D. Mitral regurgitation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Option A: MS -Trigger A. fibrillation. Option B: Hypothyroidism -Low voltage ECG, bradycardia, pericardial effusion. Option C: DCM -Damage to LA & RA - A. fibrillation Option D: MR- Leakage blood from LV to LA-trigger A. fibrillation.', 'role': 'assistant'}]