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': 'Murmur increasing with Valsalva manouvre - \nSelect and explain. \nA. Ventricular septal defect, B. HCM(hyperophic cardio myopathy), C. Mitral stenosis, D. Aoic stenosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Increases 65% of the time with hyperophic cardiomyopathy; decreased 30% of the time; Increased intensity 65% sensitive and 96% specific for hyperophic cardiomyopathy as opposed to other lesions Most other murmurs decreased intensity during Valsalva. Physiologic explanation: murmur intensity increases with decreased LV volume because of increased proximity of septum and mitral valve; decreased venous return with Valsalva Ref Harrison 20th edition pg 1446', 'role': 'assistant'}]