A 44-year-old man presents with dyspnea and new atrial fibrillation. He received a diagnosis of mild mitral regurgitation at 28 years of age but has not seen a physician in many years. Physical examination reveals a holosystolic murmur and a soft S 3 . Repeat echocardiography shows a flail posterior leaflet and moderately severe mitral regurgitation. How should this case be managed? A 44-year-old man presents with dyspnea and new atrial fibrillation. He received a diagnosis of mild mitral regurgitation at 28 years of age but has not seen a physician in many years. Echocardiography shows a flail posterior leaflet and moderately severe mitral regurgitation. How should this case be managed? Foreword This Journal feature begins with a case vignette highlighting a common clinical problem. Evidence supporting various strategies is then presented, followed by a review of formal guidelines, when they exist. The article ends with the author's clinical recommendations. Stage A 44-year-old man presents with dyspnea and new atrial fibrillation. He received a diagnosis of mitral regurgitation at 28 years of age, after physical examination revealed a midsystolic click and late-systolic murmur; echocardiography performed at that time showed mitral-valve prolapse with mild late-systolic mitral regurgitation and normal left ventricular size and function. He has not seen a physician in many years. Physical examination reveals a holosystolic murmur and a soft S 3 sound. Repeat echocardiography shows a flail posterior leaflet and moderately severe mitral regurgitation. How should this case be managed? The Clinical Problem Degenerative disease is the most . . .