Atrial septal defects

Atrial septal defects may present as:
  • Exertional dyspnoea
  • AF
  • Right heart failure
  • CVA (due to paradoxical embolus)

Clinical signs include
  • Left parasternal heave
  • Wide and fixed split of S2
  • Ejection systolic murmur, loudest at upper left sternal border
  • If a primum ASD there may be a pansystolic murmur

There are 3 main types of atrial septal defects:

1) Ostium secundum
  • caused by a large foramen ovale
  • accounts for around 75% of atrial septal defects
  • females >males
  • tends to present in adulthood
  • ECG shows RBBB with right axis deviation

2) Ostium primum
  • accounts for around 15% of atrial septal defects
  • tend to present earlier than secundum
  • ECG shows RBBB with left axis deviation and long PR
  • practically an atrioventricular septal defect as is low down in the atria, on the endocardial cushions
  • associated with Downs

3) Sinus venosus
  • usually located at junction of right atrium and superior vena cava
  • almost always associated with abnormal pulmonary venous return
  • up to 10% of ASDs

A cardiac echo may show paradoxical ventricular septal motion due to right sided overload.
Cardiac MRI is ‘gold standard’ for assessment of right ventricular size and function

Treatment is closure.

A very small atrial septal defect is patent foramen ovale. This is different from the others as as it is so small it does not allow equilisation of atrial pressures. It occurs in 25% of the population and can allow paradoxical emboli (see below) and is associated with migraine.

Complications of ASDs include:
  • Eisenmengers syndrome = left-to-right shunt causes increased blood flow through pulmonary vasculature and so pulmonary hypertension, which increases the pressure in the right side of the heart leading to reversal of the shunt to right-to-left
  • Paradoxical emboli = venous emboli cross into arterial system with potential to cause strokes, intestinal infarcts and splenic infacts
  • ?migraines – controversial area of research.
Small print gem: an eponymous syndrome that occasionally appears in MRCP answer options is Holt-Oram Syndrome, which is an inherited condition characterised by abnormalities of the heart and upper limb. It is inherited in an autosomal dominant manner with incomplete penetrance.

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Secret collector of interesting anonymised ECGs. Fan of the Bath Photomarathon. Lover of cream teas. [Sarah Hudson] (Your Picture)