Intervention in the Critically Ill Neonate and Infant with Hypoplastic Left Heart Syndrome and Intact Atrial Septum

Neonates that present with hypoplastic left heart syndrome (HLHS) and intact atrial septum (IAS) pose a major management problem for the pediatric cardiac team. They are critically ill newborns with profound hypoxemia and acidosis that require immediate attention. Controversy exists as to the most appropriate management strategy. In one series where a primary and emergent surgical-staged reconstructive procedure was performed, the in-house hospital mortality was 65% and the overall survival was 17%. With equal abysmal results, transcatheter creation of an atrial septal defect (ASD) using conventional balloon atrial septostomy (BAS) with or without the combination of blade atrial septotomy had an unacceptable high risk of cardiac perforation leading to tamponade and death. However, using more modern transcatheter techniques of transseptal perforation of the atrial septum followed by progressive and serial balloon septoplasty, creating an ASD, significantly reduced the risk of the procedure. In one series, 16 consecutive neonates underwent this type of interventional procedure without procedural mortality. The management strategy of creating an ASD in the catheterization lab followed by Stage I reconstructive surgical repair 3-5 days after the initial catheterization procedure improved the in-house survival to 57%. Unfortunately, there continues to be significant attrition of these patients undergoing Stage II and III reconstructive repair, which supports cardiac transplantation as an alternative strategy. There have been echocardiographic and histopathologic studies of these neonates, and an important echo classification of left atrial morphology has been described with perhaps some prognostic implication. In addition, autopsy specimens have demonstrated significant "arterialization" of the pulmonary venous architecture that likely dooms the patient with single ventricle physiology to a poor outcome. Future improvement in transcatheter techniques and materials offer promise in palliating these critically ill neonates. The concept of radiofrequency energy perforating catheters has great merit and may reduce the risk of cardiac perforation as compared with the rigid and long transseptal needle. Echocardiographic imaging at the time of entry through the IAS may improve the safety as well. The novel concepts of "butterfly" or "dog-bone" stents placed across the atrial septum creates a precisely sized ASD that may be more conducive to effectively lower left atrial hypertension, yet avoids excessive pulmonary blood flow associated with large atrial communications. In addition, new materials, such as the Cutting Balloon Catheter, may offer promise in creating ASDs in these patients. A more aggressive approach would be to consider intrauterine fetal transcatheter opening of the IAS using modified techniques that have been attempted for left ventricular outflow tract obstruction. Unfortunately to date, the results of attempted relief of aortic valve stenosis have been extremely poor. Finally, we as interventionalists need to continue to improve our skills to help in the complex management of these critically ill neonates and infants. Only through continued efforts of the entire cardiac team of intensivists, cardiologists, cardiothoracic surgeons, and interventionalists will our management strategy be defined to maximize the future outcome in this group of patients.