IAL SEPTAL DEFECT (ASD)

 

General:  A defect in the atrial septum that allows shunting of blood between the atria.  The direction of the shunt depends on the relative pressures between the two systems (pulmonic and systemic).

                

Prevalence:  Accounts for 10% of all congenital heart disease.  Occurs in 4/100K of the general population.  The male: female ratio is 1:2            

 

Embryology:  The atrial septum arises from two components. The septum primum grows from the upper primitive atrium while the septum secundum grows from the posterosuperior portion.  The endocardial tube twists to form the four-chambered heart.  The septum secundum covers the inferior aspect of the septum primum known as the ostium primum. The superior portion of the septum primum becomes the foramen ovale.

 ASD


             

Location:  Four types:

  1. Ostium secundum - most commom, formed by failed growth of the septum secundum, or rapid resorption of the septum primum.
  2. Sinus venosus - located high in the septum where the vena cava intersects with the right atrium, associated with anomalous venous return
  3. Ostium primum - located low in the septum and considered a type of AV septal defect. 
  4. Coronary sinus septal defect

 

Typical Presenting symptoms-

  1. Asymptomatic
  2. CHF in infancy and failure to thrive
  3. Exercise intolerance and shortness of breath, usually in the second decade of life
  4. Atrial arrhythmias
  5. Stroke secondary to paradoxical emboli from the right atrium 

 

Physical findings:

  1. III/VI systolic ejection LUSB  secondary to increased flow across pulmonic valve.  The ASD itself does not cause a murmur.
  2.  S2 widely split and fixed (i.e. does not vary with inspiration). If diastolic murmur heard, implies increased flow across tricuspid and elevated pulmonary blood flow
  3. With increased L to R shunting, may have ventricular heave

 

CXR:  Enlarged heart and increased pulmonary vascular markings with large left to right shunts.

 

EKG- With dilated RV may have right bundle branch block.  May also have atrial arrhythmias like fibrillation and flutter.

              

Echo:  Dilated RV, visualization of defect.

 

Complications:

  1. Growth failure,
  2. Atrial tachyarrhythmia
  3. Pulmonary hypertension
  4. Paradoxical emboli to brain and body

                               

Treatment: 

  1. Closure via surgery or percutaneous catheterization. Usually done electively by age 3 to avoid RV dysfunction.  If no significant shunt (<2:1), pt can be monitored periodically for development of arrhythmia or pulm HTN.
  2.  20% will spontaneously close in the first year of life, higher likelihood if less than 4 mm in diameter.  Unlikely to spontaneously close after age 3.

              

 

Treatment prognosis:  Complication rate of surgery <1%.  Closure via catheter appears to have similar success rate.  Pts usually have no restrictions.

              

Endocarditis prophy:  2007 AHA guidelines do not recommend routine antibiotic prophylaxis in children with isolated ASDs. Children with ASDs that were repaired using prosthetic materials or devices should receive prophylaxis during any dental or respiratory tract procedure that occurs within the first six months of the repair. Additionally, children s/p repair that have residual defect at or near the site of any prosthetic device (ie, valve) should also receive prophylaxis.

 


References

1.     Univeresity of Chicago Cardiology Page

2.     Vick, Bezold. ÒClassification and clinical features of isolated atrial septal defects in childrenÓ Up to Date, 2010

3.     Vick, Bezold. ÒManagement and outcome of isolated atrial septal defects in childrenÓ Up to Date, 2010.