Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a cyanotic congenital cardiac anomaly where affected individuals can have profound cyanosis and cardiac failure.

It is one of the commonest causes for a neonate to present with congestive cardiac failure and the 4th most frequent cardiac anomaly to manifest within the 1st year of life 1. The presence of an ASD and/or persistent patent foramen ovale (PFO) is crucial in residual cardiac function 1. It is fatal if untreated.

This anomaly is thought to represent 2-4% congenital cardiac anomalies 3. There is a recognised male predilection. The estimated incidence is ~ 1 in 10 000 births 6.

HLHS results from underdevelopment of left heart structures inclusive of 5 :

Associations
Plain radiograph
  • the overall cardiac silhouette may be small, normal or enlarged 1
  • may also show evidence of pulmonary venous congestion
  • the right atrial border may be prominent
Antenatal ultrasound 

The four chamber view is particularly helpful in initial in-utero assessment. May show a small ascending aorta, and a small but thick walled left ventricle while the right heart chambers may appear enlarged. The movement of the mitral valve may also appear significantly impaired.

CT/CT angiography 

CT allows direct visualisation of anomaly and vessel anatomy 2. Right-sided cardiac structures inclusive of the right ventricle, right atrium and pulmonary trunk are often enlarged as a result of compensatory effect. 

Cardiac MRI

Allows direct visualisation of anatomy while SSFP sequences may give added dynamic assessment.

HLHS can be well-tolerated in-utero due to the fetal right ventricle being the dominant chamber and the ductus arteriosus being patent.  

While previously uniformly fatal post-natally, the outlook has somewhat improved with new surgical strategies which include:

Prostaglandin E1 may be given as an initial management option to keep the ductus open.

General considerations include:

Congenital heart disease

There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorised, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.

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Article information

rID: 7407
Section: Syndromes
Synonyms or Alternate Spellings:
  • Hypoplastic left heart
  • HLHS
  • Hypoplastic left heart syndrome (HLHS)
  • Hypoplasia of the left ventricle
  • Hypoplastic left ventricle

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