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 :
- left ventricle
- mitral valve: stenosis/atresia
- aortic valve: atresia/hypoplasia
- ascending aortic root/arch
- localised concurrent aortic coarctation (can be an association in a majority of cases)
- endocardial fibroelastosis
- 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 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 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.
Allows direct visualisation of anatomy while SSFP sequences may give added dynamic assessment.
Treatment and prognosis
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:
- Norwood procedure: most commonly performed initial palliative procedure in neonatal period 5
- bidirectional cavopulmonary anastomosis (BDCPA) or hemi-Fontan procedure
- cardiac transplantation
Prostaglandin E1 may be given as an initial management option to keep the ductus open.
General considerations include:
- infantile aortic coarctation (can also be an association)
- interrupted aortic arch: consider as a differential on a four chamber fetal echocardiogram for the dilated fetal right ventricle
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.
congenital heart disease
- normal relationship between chambers and valves
- atrioventricular valves
- outflow tract
- great vessels
- venous inflow
- anomalous valves
- abnormal relationship of chambers and valves
- atrioventricular abnormality
- great vessel connection abnormality
- conotruncal cardiac anomalies
- pentalogy of Cantrell
- Shone syndrome
- congenital heart disease - chest x-ray approach
surgical repairs (mnemonic)
- arterial switch procedure
- Blalock-Taussig shunt
- double switch procedure
- Fontan procedure
- Glenn procedure
- Mustard repair
- Norwood procedure
- Pott shunt
- pulmonary artery banding
- Rastelli procedure
- Sano shunt
- Senning repair
- total repair of tetralogy of Fallot (TOF)
- unifocalisation procedure
- Waterston shunt
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