Evolution of left ventricular sphericity index in idiopathic dilated cardiomyopathy: clinical and prognostic implications

Background: To assess the significance of left ventricular (LV) sphericity index (SI) evolution at mid-term follow-up in the long-term prognostic stratification of idiopathic dilated cardiomyopathy (IDCM). LV remodeling and reverse remodeling (RR) play a leading role in the prognosis of IDCM. SI evolution as part of LVRR has not been previously investigated. Methods: We evaluated 220 IDCM patients receiving tailored treatments with available SI data at baseline and mid-term follow-up (22±6 months). Mid-term SI<0.45, assessed at 2D echocardiography, was considered expression of favorable SI evolution. In order to assess the discriminatory prognostic potential of SI evolution with respect to other predictors, Net Reclassification Index (NRI) was calculated. Results: At mid-term follow-up 51% had SI<0.45. Baseline predictors of SI<0.45 assessed at mid-term follow-up were indexed LV end-diastolic diameter and significant mitral regurgitation. During a mean follow-up of 123±66 months, deaths/heart transplant (D/HT)-free survival rates at 3, 8, and 13 years were 92%, 86%, and 76% versus 81%, 64%, and 51% in patients with mid-term SI<0.45 vs ≥0.45, respectively (p<0.001). Mid-term SI emerged as independent predictor of D/HT (HR 0.46, 95% CI 0.26-0.83, p=0.009) together with male gender, longer duration of heart failure and NYHA classes III-IV. Moreover, the evaluation of mid-term SI significantly improved risk classification in predicting outcome compared with the multivariable model without it (NRI 40% [95% CI: 15-71%]). Conclusions: Evolution of SI at mid-term follow-up in IDCM patients receiving evidence based treatments has a significant prognostic impact in the long-term, improving the prognostic stratification of this disease.