Hypoplastic left heart syndrome

Last revised by Mohamed Saber on 26 Dec 2021

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 atrial septal defect and/or persistent patent foramen ovale (PFO) is crucial in residual cardiac function 1. Hypoplastic left heart syndrome is fatal if untreated.

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

Hypoplastic left heart syndrome results from the underdevelopment of left heart structures including 5:

  • 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

The four chamber view is particularly helpful in the initial in utero assessment. It 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 allows direct visualization 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 the compensatory effect. 

Allows direct visualization of anatomy, while SSFP sequences may be used to provide an additional dynamic assessment.

Hypoplastic left heart syndrome 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 postnatally, 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:

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Cases and figures

  • Figure 1: diagram
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  • Case 1: with trisomy 13
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  • Case 2: neonate - MRI
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  • Case 3: antenatal ultrasound
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  • Case 4: antenatal ultrasound
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  • Case 5: antenatal US
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  • Case 6: with Fontan circulation
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  • Case 7
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  • Case 8
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