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 59 year old man with severe myxomatous mitral regurgitation is asymptomatic, with a left ventricular ejection fraction of 45% and an endsystolic diameter index of 2.9 cm/m2. The most appropriate treatment is: \nSelect and explain. \nA. Mitral valve repair or replacement, B. No treatment, C. ACE inhibitor therapy, D. Digoxin and diuretic therapy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (Mitral valve repair or replacement) "Surgical treatment of severe MR should be considered even in asymptomatic patients or those with mild symptoms whose LV dysfunction is progressive with LV ejection fraction declining below 60%"', 'role': 'assistant'}]