Cardiovascular Imaging

Atrial septal defect

a hole in one or more regions of the atrial septum usually conducting a left to right shunt. It may occur as an isolated anomaly or as part of a complex anomaly. The most frequent types are secundum, primum and sinus venosus defects. Rare defects are inferior vena caval or coronary sinus communications with the left atrium. The combination of large secundum and primum atrial septal defects (ASD) constitutes a common atrium. Partial anomalous pulmonary venous connection occurs with all sinus venosus defects and is also sometimes associated with other types of ASD. Isolated ASD rarely causes congestive heart failure or Eisenmengers syndrome in childhood. Even elderly patients with untreated ASD may not have Eisenmenger's syndrome. Plain radiography demonstrates pulmonary arterial hyperaemia and enlargement of the right-sided cardiac chambers and pulmonary artery.

Cardioangiography of ASD is frequently done by passage of a venous catheter across the defect and into the right upper pulmonary vein. Injection at this site depicts the site of passage of contrast media from the left into the right atrium. An injection into the pulmonary artery also displays opacification of the right atrium concurrent with the left atrium and can depict associated partial anomalous pulmonary venous connection(s). Atrial septal defects are now usually identified by two-dimensional echocardiography with colour flow mapping to depict the left to right shunt. Transoesophageal echocardiography is now being employed to guide transluminal placement of ASD closure devices. MRI can precisely depict the size and location of the ASD (Fig.1). It demonstrates a characteristic appearance of sinus venosus ASD and precisely shows anomalous pulmonary venous connections.

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Fig.1

ECG-gated spin-echo MR image shows a secundum atrial septal defect.
Atrial septal defect, Fig.1