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 commonest cardiac anomaly to manifest within the 1st year of life1. The presence of ASD and/or Persistent patent foramen ovale (PFO) is crucial in residual cardiac function1. It is lethal if untreated.

Epidemiology

Thought to represent 2 - 4 % congenital cardiac anomalies 3. There is recognised male predilection.

Pathology

Results from under development of left heart structures inclusive of 5

* left ventricle
* mitral valve : stenosis / atresia
* aortic valve : atresia / hypoplasia
* ascending aortic root / arch

Radiographic features

Plain film

* 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

CT / CTA

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.

MRI

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

Echocardiography / ultrasound

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.

Associations

* localised concurrent aortic coarctation (can be association in a majority of cases)
* endocardial fibroelastosis

Treatment and prognosis

Previously uniformly fatal. 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

Author : Dr Yuranga Weerakkody, Radiopaedia

References

* 1. Bardo et.al, Hypoplastic Left Heart Syndrome, RadioGraphics, 21, 705-717, May 2001
* 2. R. C. Gilkeson et.al, Multidetector CT Evaluation of Congenital Heart Disease in Pediatric and Adult Patients, AJR 2003; 180:973-980
* 3. Barboza et.al, Prenatal Diagnosis of Congenital Cardiac Anomalies: A Practical Approach Using Two Basic Views, RadioGraphics, 22, 1125-1138, September 2002
* 4. O'Kelly and Bove ; Hypoplastic left heart syndrome : BMJ.1997; 314: 87
* 5. Bahaaldin Alsoufi, MD et.al, New Developments in the Treatment of Hypoplastic Left Heart Syndrome,

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