Stages of Chronic Secondary MR In chronic secondary MR, the mitral valve leaflets and chords usually are normal or minimally thickened. In- stead, MR is associated with severe LV dysfunction caused by CAD (ischemic chronic secondary MR) or id- iopathic myocardial disease (nonischemic chronic sec- ondary MR). The abnormal and dilated LV causes papil- lary muscle displacement, which in turn results in leaflet tethering with associated annular dilation that prevents adequate leaflet coaptation. Secondary MR may also develop because of LA dilation and enlargement of the mitral annulus, which often occurs with AF and other cardiomyopathies. There are instances in which both primary and secondary MR are present. The best ther- apy for chronic secondary MR is not clear because MR is only one component of the disease, and restoration of mitral valve competence is not curative. The optimal criteria for defining severe secondary MR have been controversial. Compared with primary MR, adverse out- comes in secondary MR are associated with a smaller CLINICAL STATEMENTS AND GUIDELINES calculated ERO; the severity of secondary MR may in- crease over time because of adverse remodeling of the LV or mitral annulus; and Doppler methods for calcula- tions of ERO area by the flow convergence method may underestimate severity because of the crescentic shape of the regurgitant orifice.1,2 Even so, on the basis of the criteria used for determination of severe MR in RCTs of surgical intervention for secondary MR,3 6 the recom- mended definition of severe secondary MR is now the same as for primary MR (ERO 0.4 cm2 and regurgitant volume 60 mL) (Table 18). 7.3.2. Diagnosis of Chronic Secondary MR Recommendations for Diagnosis of Secondary MR Referenced studies that support the recommendations are summarized in Online Data Supplement 31. 