<qa>  What is the highest risk congenital cardiovascular malformations?Hypoplastic left heart syndrome HLHS and related single right ventricle anomalies are the highest risk congenital cardiovascular malformations. Surgical repair begins with the Norwood procedure during the newborn period, a stage II procedure at 4 to 6 months of age, and Fontan procedure at 18 to 36 months. The Norwood procedure remains one of the highest risk procedures in congenital heart surgery. A few small nonrandomized studies of a novel approach to the Norwood procedure have reported improved outcomes. This new approach uses a RV-to-PA shunt to provide pulmonary blood flow rather than the standard MBTS. This multi-center, randomized clinical trial will evaluate early and intermediate-term outcomes for patients undergoing a Norwood procedure with either the RV-to-PA shunt or the MBTS. 