Atrial Septal Defect

Atrial Septal Defect is a topic covered in the 5-Minute Clinical Consult.

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  • Anatomy
    • Opening in the atrial septum allowing flow of blood between the two atria
    • Patent foramen ovale is also an open communication between the atria, but it is not considered an ASD because no septal tissue is missing.
  • Types (by location in the interatrial septum) (1)
    • Classified based on their different anatomic location and abnormal embryogenesis: secundum ASD, primum ASD, sinus venosus ASD, coronary sinus ASD
    • 70%: Ostium secundum defect occurs in the fossa ovalis region.
    • 15–20%: Ostium primum defect occurs in the inferior septum; often associated with cleft mitral valve and failure of endocardial cushion development
    • 5–10%: Sinus venosus defect occurs in the superior-posterior septum near the orifice of the superior vena cava; usually associated with partial anomalous right upper pulmonary venous return
    • <1%: coronary sinus defect: Part of the entire common wall between the coronary sinus and the LA is absent.
  • Hemodynamic effects
    • Left-to-right shunting in late ventricular systole and early diastole
    • Degree depends on size of the defect and relative pressures of the two ventricles.
    • Causes excessive blood flow through the right-sided circulation, ultimately leading to reactive pulmonary hypertension and heart failure
  • Systems affected: cardiovascular; pulmonary
Pediatric Considerations
  • Most cases of ASD are detected and corrected in the pediatric population.
  • The smaller the defect and the younger the child, the greater the chance of spontaneous closure.


  • Predominant age: present from birth, may be diagnosed at any age
  • Slight female predominance (2)
  • No race predilection
  • 2/1,000 live births

ASDs account for 13% of congenital heart disorders.

Etiology and Pathophysiology

  • Flow across ASD usually left-to-right shunt because of higher left-sided pressures:
    • Minimal right-to-left shunting in early ventricular systole, especially during inspiration
    • Increased right-sided pressure/pulmonary hypertension can cause reversal of shunt flow (Eisenmenger syndrome) with resulting cyanosis and clubbing.
  • Symptoms typically occur due to right ventricular and pulmonary vascular volume overload and right-sided heart failure.

  • Most cases are spontaneous.
  • 5% with chromosomal abnormalities; other rare mutations exist.
  • 25% prevalence in Down syndrome

Risk Factors

  • Other congenital heart defects
  • Family history (~7–10% recurrence)
  • Thalidomide, alcohol exposure in utero, smoking, maternal age >35 years, and elevated blood glucose have been associated with increased risk (2).

Commonly Associated Conditions

  • ASDs may occur as a component of other complex cardiac structural defects.
  • Important to exclude anomalous pulmonary venous return
  • Occasionally can indicate underlying genetic syndromes, for example, Holt-Oram (ASD present in 66%), Ellis-van Creveld, VACTERL syndrome, or Noonan syndrome.
  • Overall, ~70% isolated (1)

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