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Hypoplastic Left Heart Syndrome (HLHS)

James S. Tweddell, MD, George M. Hoffman, MD, David S. Winlaw, MBBS, MD, Kathleen A. Mussatto, RN, PhD, Nancy S. Ghanayem, MD, Jeffery Phillip Jacobs, MD, Awais Ashfaq, MD, Mark Steven Bleweis, MS

Key Points

  • Without intervention, hypoplastic left heart syndrome (HLHS) is a fatal congenital heart defect.
  • In order to survive, patients with HLHS must undergo staged surgical palliation or cardiac transplantation (or both).
  • The Norwood (Stage 1) Operation is usually the first stage of palliation, followed by the Stage 2 Glenn superior cavopulmonary connection(s), and then the Stage 3 completion Fontan total cavopulmonary connection (TCPC).
  • Accurate anatomical and physiological classification is critical for management and communication.
  • HLHS is part of a broader category of congenital cardiac malformations with functionally univentricular ductal-dependent systemic circulation, which also includes "double inlet ventricle with transposed great arteries (DILV+TGA)" and "tricuspid atresia with transposed great arteries (tricuspid atresia+TGA)".
  • Genetic factors are implicated as a cause of HLHS, but the condition is heterogeneous and multigenic.
  • Early diagnosis and multidisciplinary management are essential for optimizing outcomes.
  • Patients with HLHS require lifelong longitudinal medical care and follow-up.

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Last updated: December 30, 2025