Cyanotic newborn with a single S2 is suggestive of a truncus arteriosis congenital heart defect (a VSD combined with a single ventricular outflow track comprising both the pulmonary and systemic circulation). The pulmonary circulation is thus torrential resulting in pulmonary edema. Like other CHD that result in early cyanosis, these patients are ductus-dependent for oxygenation mixing and should receive prostaglandin to maintain a PDA.