framework can be used to assist in forming a differential diagnosis, instituting therapy, and communicating with the pediatric cardiologist This approach encourages the provider to categorize patients into groups according to their age, presenting vital signs, and predominant symptoms Presentation of CHD often occurs at the time of transition from fetal to postnatal circulation The adaptation to extrauterine life involves closure of three shunts: the ductus arteriosus (DA), patent foramen ovale in the atrial septum, and ductus venosus Pulmonary vascular resistance (PVR) drops dramatically with the first breath and continues to diminish significantly over the next months It follows that closure of the DA and fall in PVR may cause infants with cardiac malformations to become symptomatic Timing of presentation correlates with these significant physiologic events Structural CHD can be divided into four major categories Each of the four categories has typical presenting symptoms due to the underlying hemodynamics The key to diagnosis is associating presenting symptoms and physical findings with each of the major categories of CHD The four categories of structural CHD are: (1) ductal dependent lesions that require a patent ductus arteriosus (PDA) for PBF; (2) ductal dependent lesions that require a PDA for systemic blood flow; (3) shunt lesions with right-to-left flow; and (4) shunt lesions with left-to-right flow ( Tables 86.1 and 86.2 ) TABLE 86.1 GLOSSARY OF CONGENITAL HEART DEFECTS Structural congenital heart defect Definition Left coronary Anomalous Left main Coronary Artery arises from the artery anomalies Pulmonary Artery rather than the aortic root (ALCAPA) Desaturated blood with low coronary perfusion pressure compromises blood flow as PVR drops in the newborn This and other variations of the coronaries may present as sudden death or CHF Aortic regurgitation Diastolic regurgitation of blood from the aorta back into (AR) the left ventricle Aortic stenosis Three types: subvalvar, valvar, and supravalvar (AS) Subtotal narrowing/obstruction of the left ventricular outflow at or near the aortic valve Aortopulmonary Defect between the aorta and pulmonary artery window Pulmonary overcirculation and left-sided volume overload Atrial septal defect A communication between the right and left atria (ASD) Usually asymptomatic Causes right-sided volume overload Atrioventricular Incomplete fusion of the embryonic endocardial cushions septal defect resulting in defects of the lower atrial septum (primum (AVSD) ASD), inlet ventricular septum, and atrioventricular valves, in isolation or combination Bicuspid aortic Aortic valve composed of two cusps, or three cusps with valve (BAV) two commissures yielding two effective cusps Congenital mitral Mitral valve leaflets are thickened and/or fused, producing stenosis a narrowed opening from the left atrium to the left ventricle, may be associated with an abnormal papillary muscle (parachute MV) Coarctation of the A discrete narrowing of the distal segment of the aortic Aorta (CoA) arch, typically just distal to the left subclavian artery at the point of ductal insertion Cor triatriatum The pulmonary veins join in a confluence that is not completely incorporated into the left atrium Double-outlet right The majority of the semilunar valve orifices of both great ventricle (DORV) Ebstein anomaly Hypoplastic left heart syndrome (HLHS) arteries arise from the morphologic right ventricle Variable presenting physiology depending on great vessel and VSD anatomy The tricuspid valve is displaced downward with resultant “atrialization” of a portion of the right ventricle The proximal part of the right ventricle is thin-walled and continuous with the right atrium and thus the functional right ventricle is small Syndrome in which the mitral valve, left ventricle, ascending aorta, and/or aortic arch are underdeveloped Cardiac output travels from the right ventricle via the main pulmonary artery to the lungs Systemic flow is blood shunted via the ductus arteriosus to the descending aorta Often the ascending aorta fills retrograde from the ductus arteriosus Blood returns to the right atrium where it is mixed with pulmonary venous return shunting from left atrium to right atrium via an ASD Systolic regurgitation of blood from the left ventricle into the left atria Mitral valve regurgitation (MR) Mitral valve Mitral valve prolapses into the left atrium after it closes, prolapse (MVP) during systole Patent ductus The ductus arteriosus, which connects the pulmonary arteriosus (PDA) artery and the aorta in the fetus, remains open after birth rather than closing within 15 hours and sealing around weeks to become ligamentum arteriosum Pulmonary atresia Pulmonary valve does not develop at all Pulmonary stenosis Narrowing near or at the pulmonary valve (PS) Pulmonary vein Defined as subtotal obstruction of one or more pulmonary stenosis veins Single ventricle Univentricular heart due to a variety of anatomic defects