Type B Interrupted Aortic Arch with a Patent Ductus Arteriosus in an Adult Presenting with Secondary Polycythaemia

Interrupted aortic arch (IAA) is an extremely rare congenital cyanotic heart disease characterized by complete disruption between the ascending and descending aorta. A patent ductus arteriosus (PDA) or other collateral pathways provide blood flow to the distal descending aorta. Mortality is extremely high at early infancy, particularly after closure of the ductus arteriosus. Survival and presentation in adulthood are extremely rare. Here, we illustrate a rare case of type B IAA in an adult who presented with secondary polycythaemia. The blood supply to the descending aorta and beyond was almost solely via a PDA. This case demonstrates the value of multimodality imaging, including CT and MRI, for diagnosis and treatment planning in these patients. LEARNING POINTS: The presence of secondary polycythaemia, as a result of chronic hypoxia, should prompt a search for underlying cyanotic heart disease even in previously undiagnosed adults. Most previous case reports of IAA in adults feature type A; type B IAA in an adult is far less frequently described. MRI has incremental value compared to CT in intracardiac assessment (aortic valve assessment, RV and LV functional assessment, flow measurement) for these patients; in addition, it provides an excellent depiction of the vascular anatomy of the aorta and great vessels.