Long-term outcome of hypoplastic left heart syndrome

Section of Cardiac Surgery, Division of Pediatric Cardiovascular Surgery, The University of Michigan School of Medicine, Ann Arbor, MI, USA
Edward L. Bove

Refinements in operative technique and perioperative care have been largely responsible for an improved outlook for newborns with hypoplastic left heart syndrome (HLHS). Staged reconstruction for patients with HLHS is based on the knowledge that an effective circulation is possible in the absence of a pulmonary ventricle. The principle that pulmonary blood flow could be maintained when certain well-defined hemodynamic criteria were met has led to the application of the Fontan procedure to virtually all forms of single ventricle lesions. The first stage in the reconstructive process, the Norwood procedure, must provide: (1) unobstructed systemic and coronary blood flow from the right ventricle, (2) unobstructed pulmonary venous return across the atrial septum, and (3) sufficient pulmonary blood flow without significant volume overload. This leaves the pulmonary and systemic circulations in parallel and the right ventricle to perform the increased volume work of both circulations. The second stage procedure, the hemi-Fontan or bidirectional Glenn operation, results in removal of the ventricular volume overload imposed by the systemic shunt and the connection of the superior vena cava to the pulmonary arteries. At the last stage of reconstruction, the Fontan procedure, inferior vena caval return is channeled to the pulmonary arteries to complete the separation of the pulmonary and systemic circulations. Although the current techniques have resulted in substantial improvements in the quantity and quality of survival, efforts to refine each stage of the process continue to evolve with increasing follow-up and evaluation.
There is no doubt that staged reconstruction now offers survival for patients with HLHS that equals that currently reported for many other forms of complex congenital cardiac malformations. Survival data compare favorably to those for patients with other forms of single ventricle, pulmonary atresia with intact ventricular septum, and even for some complex forms of tetralogy of Fallot. It is often difficult to be certain that postoperative neurologic and/or cardiovascular conditions are a result of any given operation or intervention because many of these patients were gravely ill upon presentation and prior to any procedures. Nonetheless, previous attempts to correlate preoperative condition to outcome failed to reveal an association and many patients who were moribund prior to their Norwood procedure achieved excellent late results. The effect of the operative procedures, including the use of deep hypothermia and circulatory arrest, are unclear but are currently undergoing detailed evaluation. In a recent report from our institution, neurodevelopmental outcome was normal in the majority of patients evaluated after the Fontan procedure. Although the group of patients with HLHS fared slightly less well than other patients with single ventricle lesions, most remained within the normal range. Morbidity related to the cardiovascular and respiratory systems will undoubtedly always be a part of these complex surgical interventions, but newer modifications have significantly reduced their impact.
Staged reconstruction for neonates born with HLHS offers a viable form of treatment with a good intermediate-term outcome. Survival has substantially improved and morbidity surrounding various interventions has been significantly reduced. Although it appears that most survivors grow and develop normally, it is essential to continually evaluate these patients to assess late quality of life. Current efforts aimed at reducing mortality following the Norwood operation by providing a more stable circulation and at eliminating the risk factors for the Fontan procedure would be expected to result in continued improvements in late survival.