Atrioventricular septal defect

Atrioventricular septal defects (AVSDs) comprise of a relatively wide range of defects involving the atrial septum, ventricular septum and one or both of the tricuspid or mitral valve. They can represent 2 - 7% of congenital heart defects. 

Epidemiology

The estimated prevalence is at ~ 3 - 4 of 10,000 births.

Pathology

It results from deficient development of the apical portion or the atrial septum, basal portion of the inter-ventricular septum as well as atrio-ventricular valves. All four chambers of the heart communicate therefore both left to right and right to left shunts can occur.

Classification

Many have been used but can be broadly divided into 

• complete 
• incomplete 

Associations

• Down syndrome - trisomy 21 : may be present in up to 50% of cases ⁴
• trisomy 18 : may be present in up to 25 % of cases ^ref.
• Ivermark syndrome : may be present in up to 10% of cases ⁴

Radiographic features

Plain film 

Plain film features are often not specific but may show have cardiomegaly + / - features of pulmonary hypertension and mitral valve insufficiency.

Ultrasound - echocardiography / 

Allows direct visualisation of the defect spectrum and often a large defect of the midline heart structures are seen. Colour Doppler often aids in further visualisation of the central opening.

Angiography

An AVSD can give a classical "Goose neck" sign on a lateral left ventricular angiogram ³

MRI

Allows direct visualisation of defect spectrum. Can be superior in assessing cardiac chamber dimensions and to assess the presence/extent of ventricular hypoplasia which is a determinant of surgical risk.