BACKGROUND: Options for mechanical circulatory support as a bridge to heart transplantation in children with severe heart failure are limited. METHODS: We conducted a prospective, single-group trial of a ventricular assist device designed specifically for children as a bridge to heart transplantation. Patients 16 years of age or younger were divided into two cohorts according to body-surface area (cohort 1, <0.7 m2; cohort 2, 0.7 to <1.5 m2), with 24 patients in each group. Survival in the two cohorts receiving mechanical support (with data censored at the time of transplantation or weaning from the device owing to recovery) was compared with survival in two propensity-score-matched historical control groups (one for each cohort) undergoing extracorporeal membrane oxygenation (ECMO). RESULTS: For participants in cohort 1, the median survival time had not been reached at 174 days, whereas in the matched ECMO group, the median survival was 13 days (P<0.001 by the log-rank test). For participants in cohort 2 and the matched ECMO group, the median survival was 144 days and 10 days, respectively (P<0.001 by the log-rank test). Serious adverse events in cohort 1 and cohort 2 included major bleeding (in 42% and 50% of patients, respectively), infection (in 63% and 50%), and stroke (in 29% and 29%). CONCLUSIONS: Our trial showed that survival rates were significantly higher with the ventricular assist device than with ECMO. Serious adverse events, including infection, stroke, and bleeding, occurred in a majority of study participants. Copyright © 2012 Massachusetts Medical Society.