Echocardiography is used to measure the therapeutic effectiveness of heart failure therapy in adults and children. The purposes of this study were (1) to assess baseline echocardiographic predictors of clinical outcome, (2) to investigate changes in echocardiographic parameters, and (3) to compare these echocardiographic changes with changes in plasma levels of b-type natriuretic peptide (BNP) in a population of children with systemic ventricular dysfunction and symptomatic heart failure treated with carvedilol or placebo. All available baseline and 6-month echocardiograms from Pediatric Carvedilol Trial (PCT) participants (carvedilol n = 161; placebo n = 55) were reviewed. Systolic and diastolic sphericity index (SI; n = 110), TEI index (n = 145), and systemic ventricular dP/dt (n = 70) were measured. The PCT composite definition of clinical outcome (i.e., worsened, improved, or unchanged) was used. For all patients, baseline TEI index was a predictor of worsened outcome. Only children treated with carvedilol showed a significant decrease in systolic SI (P ≤ 0.0001), diastolic SI (P ≤ 0.0001), and TEI index (P = 0.02). An inverse correlation between changes in BNP and changes in dP/dt (r = –0.45, P = 0.04) was found only in the carvedilol group. In conclusion, TEI index predicted outcome in children with systemic ventricular dysfunction and heart failure. Carvedilol may have a beneficial effect on reversal of left ventricular remodeling and global ventricular function in pediatric heart failure.