**12. Down syndrome**

Around 36.5–66% of Down patients have pulmonary hypertension with congenital heart disease less than six months of age [5, 57]. There has been controversy about the extent of pulmonary vascular changes with Down and non-Down syndrome patients. There are studies which showed earlier development of pulmonary parenchymal hypoplasia and pulmonary vascular obstructive disease (PVOD) in this patient population [58–60]. In children with Down syndrome, Rastelli type A is most common. But when associated with tetralogy of Fallot, Rastelli type C is common. In unbalanced AVSDs, left ventricular dominance is more common [6]. It's known that this patient population tolerates single ventricle physiology poorly [61]. Nevertheless, surgical outcomes are not different for biventricular repair when compared with non-Down syndrome patients. Survival at 30 years was 85.6% for complete AVSD, in patients with trisomy 21 [62].
