The hypoplastic left heart syndrome with intact atrial septum: Atrial morphology, pulmonary vascular histopathology and outcome

OBJECTIVES The purpose of this study was to investigate the outcome in infa nts with hypoplastic left heart syndrome and intact atrial septum and to ev aluate the relationship of atrial morphology, left atrial decompression pat hway and lung histopathology to outcome. BACKGROUND In the hypoplastic left heart syndrome, severe restriction at th e atrial level results in marked systemic hypoxemia after birth. Infants wi th intact atrial septum may be at high risk for mortality after Norwood ope ration. METHODS Of 316 infants with hypoplastic left heart syndrome seen at our cen ter over a 6.5-year period, 18 (5.7%) had intact atrial septum. Medical rec ords and echocardiograms were reviewed. RESULTS On echocardiography, three types of intact atrial septal morphology were identified: 1) large left atrium, thick prominent septum 2 degrees wi th thin septum 1 degrees adherent (type A, n = 12); 2) small left atrium wi th thick, muscular atrial septum (type B, n = 4), and 3) giant left atrium, thin atrial septum with severe mitral regurgitation (type C, n = 2). Seven infants had left atrial decompression pathways that were severely obstruct ed (3/12 type A, 4/4 type B). Norwood operation was performed in 17 infants ; one underwent emergency balloon atrial septostomy and died. Of six early survivors, all with type A atrial morphology and unobstructed decompression pathway; three died after subsequent cavopulmonary surgery. Lung histopath ology revealed severely dilated lymphatics and "arterialization" of the pul monary veins in those with the severest degree of obstruction to left atria l egress (type B atrial morphology). CONCLUSIONS Despite aggressive intervention, outcome for infants born with hypoplastic left heart syndrome and intact atrial septum is poor. Maldevelo pment of the pulmonary vasculature contributes to the high mortality seen. Atrial morphology can be used as a marker for the severity of pulmonary vas cular disease. (C) 1999 by the American College of Cardiology.