Defining the Spectrum of Hypoplastic Left Heart Syndrome (HLHS)

Area of Science:

• Cardiology
• Pediatric Cardiology
• Medical Diagnostics

Background:

• Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect.
• Standardized definitions are crucial for accurate diagnosis and classification.
• The 2021 International Paediatric and Congenital Cardiac Code and ICD-11 provide updated definitions.

Purpose of the Study:

• To present the definition of Hypoplastic Left Heart Syndrome (HLHS) as per the 2021 International Paediatric and Congenital Cardiac Code and ICD-11.
• To clarify that HLHS encompasses a spectrum of conditions, including those with intact ventricular septum (HLHS+IVS) and ventricular septal defect (HLHS+VSD).

Main Methods:

• Review and synthesis of the official definitions provided by the 2021 International Paediatric and Congenital Cardiac Code.
• Analysis of the diagnostic criteria for HLHS, including specific cardiac malformations.
• Comparison of different HLHS phenotypes, such as HLHS+IVS and HLHS+VSD.

Main Results:

• HLHS is defined as a spectrum of congenital cardiovascular malformations characterized by left heart underdevelopment.
• Key features include hypoplasia of the left ventricle, mitral and/or aortic valves, ascending aorta, and aortic arch.
• Both HLHS+IVS and HLHS+VSD are recognized as part of the HLHS spectrum despite phenotypic differences.

Conclusions:

• The provided definition offers a comprehensive understanding of HLHS as a spectrum of defects.
• Accurate classification of HLHS phenotypes is essential for clinical management and research.
• The definition ensures consistency in diagnosing and reporting HLHS cases globally.