Hypoplastic Left Heart Syndrome Across the Lifespan: Clinical Considerations for Care of the Fetus, Child, and Adult.

Hypoplastic left heart syndrome (HLHS) is the most common anatomic lesion in children born with single-ventricle physiology and is characterised by the presence of a dominant right ventricle and a hypoplastic left ventricle along with small left-sided heart structures. Diagnostic subgroups of HLHS reflect the extent of inflow and outflow obstruction at the aortic and mitral valves, specifically stenosis or atresia. If left unpalliated, HLHS is a uniformly fatal lesion in infancy. Following introduction of the Norwood operation, early survival has steadily improved over the past 4 decades, mirroring advances in operative and perioperative management as well as reflecting refinements in patient surveillance and interstage clinical care. Notably, survival after staged palliation has increased from 0% to a 5-year survival of 60%-65% for children in some centres. Despite the prevalence of HLHS in childhood with relatively favourable surgical outcomes in contemporary series, this cohort is only now reaching early adult life and longer-term outcomes have yet to be elucidated. In this article we focus on contemporary clinical management strategies for patients with HLHS across the lifespan, from fetal to adult life. Nomenclature and diagnostic considerations are discussed and current literature pertaining to putative genetic etiologies is reviewed. The spectrum of fetal and paediatric interventional strategies, both percutaneous and surgical, is described. Clinical, patient-reported, and neurodevelopmental outcomes of HLHS are delineated. Finally, note is made of current areas of clinical uncertainty, and suggested directions for future research are highlighted.