Evolution of care pathways for babies with hypoplastic left heart syndrome: integrating mechanistic and clinical process investigation, standardization, and collaborative study

Since initial descriptions of staged palliation for hypoplastic left heart syndrome (HLHS) in the 1980’s, much has been learned about the pathophysiology of the single ventricle circulation. New therapies that leverage systems biology and clinical derivatives have been developed. While in-hospital mortality and morbidity for babies with HLHS have continued to improve, there remains a long (and daresay winding) road ahead to achieve ideal outcomes. Important variation in even these abbreviated in-hospital metrics persists among institutions and currently utilized prediction models explain only a small amount of this variation. Moreover, long-term survival and neurodevelopmental health for patients with HLHS are infrequently reported and remain suboptimal despite improved in-hospital outcomes. This focused review will describe the evolution of national outcomes for HLHS over time and the potential factors motivating improved time-related mortality. Emerging modifiable risk-factors that hold promise in terms of moving the needle for long-term success, including social determinants of health and the delineation of genetic profiles, will be discussed. Specifically, this review will integrate contemporary data based on the first murine HLHS models that suggest a genetically elicited modular phenotype with environmental factors known to impact the initial durability of surgical therapies. A comprehensive approach to the management of HLHS, which leverages both proactive transplantation and hybrid palliation, in addition to traditional Norwood palliation, will be emphasized to extend and match management to the complete spectrum of patient risk- profiles. Finally, we will explore the critical role that national collaboratives and quality reporting initiatives have played in improving outcomes and shifting the focus to more meaningful long-term survival and neurodevelopment.