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Functionally Univentricular Heart (Single Ventricle)

Mohamad Alaeddine, Christopher E. Mascio, MD

Key Points

  • The term “functionally univentricular heart” is defined as "a spectrum of congenital cardiac malformations in which the ventricular mass may not readily lend itself to partitioning that commits one ventricular pump to the systemic circulation, and another to the pulmonary circulation".
  • Although the term “functionally univentricular heart” and the term "single ventricle" are often used as synonyms, the term "single ventricle" is somewhat of a misnomer because in these hearts, a rudimentary second ventricle is usually present but only one ventricle is functionally adequate.
  • The “functionally univentricular heart” is categorized into major groups, including hypoplastic left heart syndrome (HLHS), double-inlet atrioventricular connections (e.g., DILV, DIRV), absence of one atrioventricular connection (e.g., tricuspid atresia or mitral atresia), unbalanced atrioventricular canal, heterotaxy with one developed ventricle, and other complex lesions.
  • At birth, systemic and pulmonary circulations are in parallel, making initial management dependent on the balance of pulmonary blood flow, the presence of systemic outflow obstruction, and the status of the pulmonary venous return. Precise anatomical classification is essential for surgical planning and communication.

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Last updated: January 7, 2026