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Figure 1: Schematic diagram showing the distribution of blood flow between the systemic and pulmonary circulation in infants with type B interrupted aortic arch in two situations. In (a), a PA crisis shunts blood from right to left across the PDA (straight arrow) and the VSD (curved arrow) at the expense of pulmonary blood flow (crossed lines). Thus no/minimal saturation and pressure differential (dashed arrows) exists in pre- and postinterrupted circulations. In (b), the reverse situation occurs with acute closure of PDA (crossed line); the ductal dependant systemic output drops and a pressure differential is discernable between the ductal (post-interrupted) and nonductal (pre-interrupted) circulations (dashed arrows). The shunting across the VSD would depend on the relative compliances of the left and right ventricle and may become bidirectional (bidirectional arrow). RV - right ventricle; RA - right atrium; MPA - main pulmonary artery; LPA - left pulmonary artery; RPA - right pulmonary artery; PDA - patent ductus arteriosus; AO - ascending aorta; DTA - descending thoracic aorta

Figure 1: Schematic diagram showing the distribution of blood flow between the systemic and pulmonary circulation in infants with type B interrupted aortic arch in two situations. In (a), a PA crisis shunts blood from right to left across the PDA (straight arrow) and the VSD (curved arrow) at the expense of pulmonary blood flow (crossed lines). Thus no/minimal saturation and pressure differential (dashed arrows) exists in pre- and postinterrupted circulations. In (b), the reverse situation occurs with acute closure of PDA (crossed line); the ductal dependant systemic output drops and a pressure differential is discernable between the ductal (post-interrupted) and nonductal (pre-interrupted) circulations (dashed arrows). The shunting across the VSD would depend on the relative compliances of the left and right ventricle and may become bidirectional (bidirectional arrow). RV - right ventricle; RA - right atrium; MPA - main pulmonary artery; LPA - left pulmonary artery; RPA - right pulmonary artery; PDA - patent ductus arteriosus; AO - ascending aorta; DTA - descending thoracic aorta