pediatrics
Hypoplastic Left Heart Syndrome
Introduction
Hypoplastic left heart syndrome consists of hypoplasia of the left ventricle and ascending aorta, maldevelopment and hypoplasia of the aortic and mitral valves (frequently aortic atresia is present), an atrial septal defect, and a patent ductus arteriosus. Unless normal closure of the patent ductus arteriosus is prevented with prostaglandin infusion, cardiogenic shock and death ensue within the first several days of life. A loud, single second heart sound (S2) and nonspecific systolic murmur are common. Diagnosis is by emergency echocardiography. Definitive treatment is staged surgical correction or heart transplantation. (See also Overview of Congenital Cardiovascular Anomalies .) Hypoplastic left heart syndrome (HLHS) accounts for 2 to 4% of congenital heart anomalies and is the second most common left heart obstructive lesion. Because the mitral valve, left ventricle, and aortic valve are hypoplastic (often with aortic atresia), oxygenated blood coming into the left atrium from the lungs is diverted across the atrial communication into the right heart, where it mixes with desaturated systemic venous return (see figure). This relatively desaturated blood exits the right ventricle through the pulmonary artery to the lungs and through the ductus arteriosus to the systemic circulation. Systemic blood flow is maintained only through the right-to-left ductal shunt; thus, immediate survival depends on patency of the ductus arteriosus. The left ventricle, ascending aorta, and aortic and mitral valves are hypoplastic; an atrial septal defect and a large patent ductus arteriosus are also present. AO=aorta; IVC=inferior vena cava; LA=left atrium; LV=left ventricle; PA=pulmonary artery; PDA=patent ductus arteriosus; PV=pulmonary veins; RA=right atrium; RV=right ventricle; SVC=superior vena cava. 