Any infant who has a murmur and appears cyanotic ( Fig 35.1A ) should have a thorough physical examination, pulse oximetry, EKG, CXR, and echocardiography following assessment and support of their ABCs If the physical examination is normal, except for the perceived cyanosis and the murmur, and the EKG, CXR, and pulse oximetry are normal, the infant probably has a clinically insignificant murmur and a noncardiac cause of his/her cyanosis (peripheral acrocyanosis, polycythemia, methemoglobinemia) These patients not require emergent cardiology consultation If an otherwise well-appearing cyanotic infant has an abnormal EKG, CXR, and diminished oxygen saturation, the baby probably has cyanotic heart disease The differential diagnosis for such a patient includes tetralogy of Fallot, transposition of the great vessels with single ventricle, truncus arteriosus, Ebstein anomaly, tricuspid atresia with patent foramen ovale, anomalous pulmonary venous drainage, or moderately severe pulmonary stenosis with right-to-left shunting through an atrial or ventricular septal defect or a patent ductus Pediatric cardiology consultation should be obtained for all of these patients Neonates should be admitted to the hospital for evaluation and treatment If the cyanotic infant is ill-appearing, pulse oximetry, CXR, and/or EKG will likely be abnormal If the findings on examination suggest CHF and/or cardiogenic shock, the infant likely has severe cyanotic congenital heart disease or an extremely severe acyanotic defect with the cyanosis related to poor perfusion and failure The possibility of primary pulmonary hypertension should also be considered and steps initiated toward treatment with either inhaled nitrous oxide or extracorporeal membrane oxygenation Survival of patients with these severe lesions is dependent on maintaining patency of the ductus arteriosus Early infusion therapy with prostaglandin E1 (alprostadil) under carefully controlled monitoring and emergent cardiology consultation is recommended (see Chapter 86 Cardiac Emergencies ) In the older cyanotic infant, additional considerations include large arteriovenous malformation, atrioventricular canal defect, and large ventricular septal defect These infants should be admitted to the hospital or transferred to a pediatric cardiac center for further evaluation and treatment If the evaluation of the ill-appearing cyanotic infant does not suggest CHF or shock, and the saturation improves with crying and oxygen, the infant likely has primary lung disease due to infection, hypoperfusion, or pulmonary arteriolar hypertension These infants should be admitted for further evaluation and treatment with concurrent close monitoring of the murmur If an infant without cardiac disease presents with persistent low oxygen saturation despite