Atrial Septal Defect (ASD)

There are two main types of ASD:

• Secundum ASD (80% of ASDs)
• Partial atrioventricular septal defect (primum ASD, pAVSD)

Both present with similar symptoms and signs, but their anatomy is quite different. The secundum ASD is a defect in the centre of the atrial septum involving the foramen ovale. Partial AVSD is a defect of the atrioventricular septum.

Animation: Secundum ASD

Clinical features

Symptoms

• None (commonly)
• Recurrent chest infections/wheeze
• Arrhythmias (fourth decade onwards)

Physical Signs

• An ejection systolic murmur best heard at the upper left sternal edge – due to increased flow across the pulmonary valve because of the left-to-right shunt
• A fixed and widely split second heart sound (often difficult to hear) – due to the right ventricular stroke volume being equal in both inspiration and expiration
• With a partial AVSD, an apical pansystolic murmur from atrioventricular valve regurgitation

Investigations

Chest radiograph

Finding:

• Cardiomegaly
• Enlarged pulmonary arteries
• Increased pulmonary vascular markings

ECG

Finding:

• Secundum ASD – partial right bundle branch block is common (but may occur in normal children), right axis deviation due to right ventricular enlargement
• Partial AVSD – a ‘superior’ QRS axis (mainly negative in AVF). This occurs because there is a defect of the middle part of the heart where the atrioventricular node is. The displaced node then conducts to the ventricles superiorly giving the abnormal axis

Echocardiography

Finding:

• This will delineate the anatomy and is the mainstay of diagnostic investigations

Management

Children with significant ASD will require treatment. For secundum ASDs this is by cardiac catheterisation with insertion of an occlusion device but for partial AVSD surgical correction is required.

Treatment is usually undertaken at about 3-5 years of age in order to prevent right heart failure and arrhythmias in later life.