Coarctation of the aorta is a narrowing of the aortic arch. It most commonly occurs in the region of the aortic isthmus (distal aortic arch near the descending aorta). Patients with a severe coarctation of the aorta are dependent on a patent ductus arteriosus (PDA) to preserve systemic blood flow and perfusion. Coarctation represents a spectrum of disease from an isolated narrowing to diffuse hypoplasia of the entire aortic arch. There is an association with additional lesions such as bicuspid aortic valve or ventricular septal defects.