ASD – Atrial Septal Defect
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An Atrial septal defect is a congenital heart defect that causes a shunting of blood from the left to the right atria.

L-to-R shunt – ACYANOTIC
There are two types of Atrial Septal Defect:

  • Secundum ASD
    • 80% of ASD’s
    • Basically, a patent foramen ovale
  • Partial AVSD
    • Minority of cases
    • Usually involves a defect around the bottom of the atrial septum, and typically involves the tricuspid valve
  • Clinical features of both types are very similar
  • In both instances, blood will flow from left to right through the defect
 Atrial Septal Defect

Clinical features

  • Commonly asymptomatic
  • Recurrent chest infections / wheeze
  • Heart failure
  • Arrythmias – not until >4th decade of life


  • Split second heart sound
  • Ejection systolic murmur – best heard at the left sterna edge – due to increase bloodflow in the right ventricular outflow tract


CXRmay show cardiomegaly, and increased pulmonary markings
  • Secundum
    • RBBB (but this is common in many children anyway)
    • Right axis deviation
  • Partial AVSD
    • Left axis deviation
    • Superior QRS axis – the AVSD is typically in the region of the AV node, thus conduction is altered, and conduction occurs to the ventricles ‘superiorly’


Secundum ASD
  • Usually cardiac catheterisation. A device can be inserted to close off the defect

Partial AVSD

  • Surgery usually required
  • Usually performed at age 3-5 to prevent prevent RHF and arrhythmias in later life


  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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