Intermittent acute profound cyanosis in patients with EA-TEF is usually due to near complete collapse of the trachea. However, the possibility of an anatomical shunt has to be ruled out because congenital heart malformations associated with right-to-left shunts (such as valve atresia, Tetralogy of Fallot, anomalous pulmonary venous return, and septal defects or patent ductus arteriosus) are present in more than one quarter of the patients80,84 and they are independent predictors of survival125. For children with no history of congenital heart disease an echocardiogram is useful in order to investigate for presence of vascular abnormalities such as right-sided or double aortic arch, and aberrant right or left subclavian arteries that may complicate the clinical presentation by causing or exacerbating the degree of tracheomalacia37,78,80,81,126. Definitive confirmation will require a CT-angiogram or an MRI/MRA or cardiac catheterization.