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A congenital defect characterised by abnormal communication between the atria, allowing left-to-right shunting of blood.
A congenital defect characterised by abnormal communication between the atria, allowing left-to-right shunting of blood.
Risk Factors
Trisomy 21 (especially AVSD type)
Fetal alcohol syndrome
Maternal diabetes
Familial CHD history
Aetiology
Failure of septum primum or secundum formation during fetal development
Types: secundum (most common), primum (associated with AVSD), sinus venosus
Pathophysiology
Left-to-right atrial shunt due to pressure gradient
↑ blood flow to right atrium and right ventricle → right-sided volume overload
Pulmonary overcirculation and eventually pulmonary hypertension if uncorrected
Possible development of paradoxical emboli if shunt reverses (Eisenmenger’s)
Diagnosis
Often asymptomatic in infancy and childhood
Murmur usually detected on routine exam
Wide fixed split of S2, systolic ejection murmur (↑ flow across pulmonary valve)
Large ASD: fatigue, SOB with exertion, frequent respiratory infections
Adult presentation: arrhythmia (esp. atrial fibrillation)
Differential Diagnosis
VSD
PDA
Pulmonary stenosis
Partial anomalous pulmonary venous return
AVSD
Investigations
Echocardiography – diagnostic, including bubble contrast or transoesophageal echo for small shunts
ECG – right axis deviation, RBBB
CXR – cardiomegaly, ↑ pulmonary vasculature
Cardiac catheterisation – assess pulmonary pressures if large or late diagnosis
Management
Small ASDs may close spontaneously – observe
Secundum ASDs with significant shunting – percutaneous device closure typically after age 2
Primum or sinus venosus defects – surgical repair
Anticoagulation if associated arrhythmia or paradoxical embolus
Complications
Pulmonary hypertension and Eisenmenger’s syndrome
Arrhythmias – atrial fibrillation, flutter
Right heart failure
Stroke or TIA due to paradoxical embolus
Residual shunt post-repair
Prognosis
Excellent after closure, especially if done before pulmonary hypertension develops
Lifelong follow-up for large or complex repairs
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