Atrial septal defect

What it is

Atrial septal defect is a non-cyanotic congenital heart defect with a left to right shunt, and it belongs in that group beside VSD and PDA. The other non-cyanotic group is outflow obstruction, which holds AS, PS and coarctation of aorta; the cyanotic defects, such as transposition of great vessels, are a separate class. ASD is associated with Trisomy 21, and the murmur that is associated with Down belongs to AVSD, not to ASD. Of its types the secundum is the most common.

How it presents

Commonly it is asymptomatic, which is why it can go for decades before anything is seen. When there are symptoms they are:

• Recurrent chest infections or wheeze
• Arrhythmias, from the fourth decade onwards

How it is diagnosed

Two clinical findings carry the diagnosis: an ejection systolic murmur, and wide fixed splitting of A2. Fixed splitting means a second heart sound that does not vary with respiration. ASD sits among the causes of an ejection systolic murmur beside AS, PS and HOCM, so the murmur alone does not name it. Chest x-ray adds three findings:

• Cardiomegaly
• Enlarged pulmonary arteries
• Increased pulmonary vascular markings