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Atrial septal defect

Thompson, Erin MPH, MMS, PA-C

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Journal of the American Academy of PAs: June 2013 - Volume 26 - Issue 6 - p 53-54
doi: 10.1097/01.JAA.0000430348.81563.f1
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  • Atrial septal defect (ASD) is a congenital heart defect that enables blood flow between the left and right atria through a defect in the interatrial septum.
  • Occurs due to failure of foramen ovale to close despite change in pulmonary pressure at birth, a condition known as a patent foramen ovale
  • Results in mixing of arterial (high oxygen content) and venous (low oxygen content) blood
  • The mixing of blood can cause a left-to-right shunt that can reverse to a right-to-left shunt over time. This complication is known as Eisenmenger syndrome.
  • Right-to-left shunts cause more complications, such as right heart failure and pulmonary hypertension.
  • ASDs are present in 1.64 of every 1,000 live births.
  • ASDs compose 35% to 40% of congenital heart defects, making them the second most common congenital heart defect.
  • The male to female ratio is 1:2.
  • Familial recurrence rate is about 10%.
  • Ostium secundum, an opening in the atrial wall at the site of the foramen ovale, is the most common type of ASD.


  • Most patients with ASDs are diagnosed in utero or early childhood due to advances in ultrasonography and auscultation during the physical exam.
  • Symptoms of ASD are related to size of the defect.
    • Small to medium ASDs may not cause symptoms in early childhood.
    • Infants with large ASDs may have cyanosis, heart failure, recurrent respiratory infections, or failure to thrive.
  • Adults who were not diagnosed in childhood typically present by their 30s or 40s with
    • Dyspnea on exertion
    • New-onset heart failure
    • Stroke
    • Atrial fibrillation
  • In patients who have long-standing ASD, a switch to a right-to-left shunt may result in cyanosis evident on physical exam.
  • The findings on physical examination depend on the size and location of the defect.
    • Palpation of the precordium: right ventricular heave most noticeable on the left sternal border. A left upper sternal border impulse may be noted if the patient has pulmonary hypertension.
    • Heart sounds: A wide, fixed, split S2 is characteristic of ASD and is best evaluated when the patient is sitting or standing.
    • Additional murmurs that may be auscultated include:
      • Mid-systolic pulmonary flow or ejection murmur, noted in larger left-to-right shunts
      • A low-pitched diastolic murmur, which can be heard when the pulmonary artery has dilated
      • A late apical or holosystolic murmur radiating to the axilla, found in patients with mitral regurgitation due to ASD
      • A diastolic rumble increased with inspiration can be noted in patients with left-to-right shunts, and is caused by increased flow across the tricuspid valve.
      • An S4 will be noted in patients with pulmonary hypertension due to ASD.
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  • Echocardiogram
    • Test of choice for diagnosis
    • Transthoracic echocardiogram (TTE) with color Doppler will show jet of blood from left to right atrium.
    • A bubble study can be conducted. Bubbles moving from right to left atrium indicate that right atrial pressure is higher.
    • Transesophageal echocardiogram may be required if the ASD is not visualized on TTE or to aid in sizing and determining concomitant abnormalities.
  • Chest X-ray
    • May be normal
    • Later in life, may show enlarged cardiac silhouette and pulmonary edema
    • In patients with sinus venous defect (a defect close to the superior or inferior vena cava), the “scimitar sign” may be seen. This is a vertical, curved right-sided pericardiac linear density that increases in width as it approaches the right cardiophrenic angle.
  • ECG
    • Prolonged PR interval in patients with first-degree heart block
    • Incomplete right bundle branch block
    • Notched R wave in inferior leads
    • Left axis deviation of QRS, most commonly seen in primum ASDs, which are communications present at the level of the mitral or triscupid valves
    • Right axis deviation of QRS (ostium secundum ASD)
    • Left axis deviation of P wave (sinus venous defect)


  • Treatment options are determined based on time of discovery and size and location of defect.
  • Patients with significant pulmonary hypertension are best treated symptomatically for heart failure.
  • Surgical correction is ideal before pulmonary hypertension develops, and has the lowest risk of complications when performed in patients<25y. Closure may be performed as open heart surgery or, more common, percutaneously.


  • Decompression sickness
  • Paradoxical emboli
  • Eisenmenger syndrome
  • Pulmonary hypertension
  • Right-sided heart failure
  • Atrial fibrillation or flutter.
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© 2013 American Academy of Physician Assistants.