A septal defect is a hole (opening) in the wall (septum) that divides two chambers of the heart. Depending on which septum is affected, the defect is classified as an atrial septal defect (ASD) or a ventricular septal defect (VSD).
An atrial septal defect is a hole in the wall between the right and left atria (the upper chambers). Small ASDs may cause no symptoms and close spontaneously in childhood; larger ones allow a continuous left-to-right shunt that can, over time, cause right heart enlargement, atrial fibrillation and, if untreated, pulmonary hypertension.
A ventricular septal defect is a hole in the wall between the right and left ventricles (the lower chambers). Like ASDs, small VSDs are often asymptomatic and may close spontaneously. Larger VSDs cause a significant shunt and can lead to heart failure in infancy or, if untreated and large, pulmonary hypertension and Eisenmenger syndrome in adulthood. A small, benign VSD producing a loud murmur without haemodynamic significance is known as Maladie de Roger.
Both ASD and VSD closure can be achieved by catheter-based device implantation (for anatomically suitable defects) or by open-heart surgery. For cardiac arrest survivors found incidentally to have a septal defect on echocardiography, the defect itself is unlikely to be the cause of the arrest unless it is associated with severe pulmonary hypertension or Eisenmenger syndrome, and investigation for arrhythmia substrates should continue in parallel.
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