MR may develop in patients with preserved LV systolic function who have progressive LA dila- tion, leading to enlargement of the mitral annu- lus and malcoaptation of the leaflets.51,52 This may arise in conditions such as HF with preserved LVEF, restrictive cardiomyopathy, and nonobstruc- tive hypertrophic cardiomyopathy. These patients often have associated AF, which may contribute to the progression of LA and annular dilation, thus increasing the severity of MR,18,53 and suc- cessful ablation of AF may reduce or eliminate Isolated annular dilation accounts for <20% of patients referred for surgery of severe MR in the STS database, but it is also the etiology with CLINICAL STATEMENTS AND GUIDELINES the highest mitral valve repair rates (85%).16,17 The limited data addressing mitral valve repair in patients with annular dilation related to AF indi- cate low operative risk.18 20 4. There is limited evidence that mitral valve sur- gery improves survival in symptomatic patients with secondary MR. In addition, surgery may improve symptoms and quality of life in these patients whose symptoms persist despite GDMT. Small RCTs demonstrate that mitral valve surgery reduces chamber size and improves peak oxygen consumption in chronic severe secondary MR. Ischemic or dilated cardiomyopathy presents dif- ferent challenges for mitral repair. Regurgitation is caused by annular dilation, as well as by apical and lateral displacement of the papillary muscles. New techniques have facilitated mitral repair in this situation, but durability of the repair is dependent primarily on regression or progression of ventricular dilation. If the heart continues to dilate, long-term durability of the repair is moot; the survival of the patient is limited.9,12,21 43 5. 