Table 1.

DA in specific critical congenital cardiac defects.

Role of DA	Examples	Clinical findings
DA required for adequate pulmonary blood flow (PBF)	Tetralogy of Fallot depending on degree of pulmonary stenosis Double-outlet right ventricle with subaortic ventricular septal defect (VSD) and pulmonary stenosis Tricuspid atresia Pulmonary atresia Critical pulmonary stenosis Severe Ebstein’s anomaly Single ventricle with pulmonary stenosis	Infant presents with cyanosis and hypoxia Inadequate PBF initially manifests with systolic hypotension due to compromised left ventricle preload followed by diastolic (combined) hypotension
DA required for adequate systemic blood flow (SBF)	Aortic stenosis Coarctation of the aorta Aortic arch interruption Hypoplastic left heart syndrome Multiple left heart defects	Infant presents with signs of poor perfusion with weak or absent pulses in lower extremities Inadequate SBF manifests with profound systolic hypotension and may progress to shock
DA required for right to left shunt to ensure adequate atrial level mixing in parallel circulations with poor mixing	d-transposition of great arteries d-transposition of great arteries and VSD Double-outlet right ventricle with sub-pulmonary VSD	Infant may present with early profound hypoxia in presence of restrictive PFO Parallel circulations without mixing ultimately results in profound, lethal systemic hypoxia
DA may contribute to increased PBF and cyanosis in lesions with complete mixing	Total anomalous pulmonary venous connection Truncus arteriosus Single ventricle without pulmonary stenosis Double-outlet right ventricle with sub-aortic VSD and without significant pulmonic stenosis	Infant usually presents with mild hypoxia Infants with obstructed pulmonary venous connection will present with profound systemic hypoxia and systolic hypotension

DA, ductus arteriosus.