Atrial Septal Defect

Introduction

An Atrial Septal Defect (ASD) is 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).          

asd_0.jpg
http://en.wikipedia.org/wiki/Atrial_septal_defect

Prevalence:  

ASD's account for 10% of all congenital heart disease.  They occur 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.  

embryo_1.png
http://en.wikipedia.org/wiki/Atrial_septal_defect

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.

Location:         

Four types:

types.png
 HV: right ventricle;VCS: superior vena cava; VCI: inferior vena cava;
http://en.wikipedia.org/wiki/Atrial_septal_defect

  1. Ostium secundum (3) - most common, formed by failed growth of the septum secundum, or rapid resorption of the septum primum.
  2. Sinus venosus (1  upper sinus venosus, 2  lower sinus venosus) - located in the septum where the vena cava intersects with the right atrium, associated with anomalous venous return
  3. Ostium primum (5) - located low in the septum and considered a type of AV septal defect. 
  4. Coronary sinus septal defect (4)

 

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:                                                            Audio Example

  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.

cxr_1.jpg
http://en.wikipedia.org/wiki/Atrial_septal_defect

EKG- 
With a dilated RV, there may be a right bundle branch block.  There may also be atrial arrhythmias like fibrillation and flutter.

Echo:  
Demonstrates a dilated RV, and allows visualization of the defect.

echo.jpg
Subcostal view of the heart, the apex is towards the right, atria to the left. ASD secundum seen as a discontinuation of the white band of the atrial septum. Enlarged right atrium below. Enlarged pulmonary veins seen entering left atrium above.
http://en.wikipedia.org/wiki/Atrial_septal_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 (now a standard in developed countries). 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.

patch.png
http://en.wikipedia.org/wiki/Atrial_septal_defect

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.

 

Prognosis:  

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

Endocarditis Prophylaxis:

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.

Check the American Heart Association (LINK BELOW) for the most up to date recommendations.

AHA_2.jpg

Click on the wallet card below, print it out, and give it to families as a reminder of the need for prophylaxis. The card also contains information on what antibiotics to use, and specific dosing instructions.

card.jpg
www.heart.org

Click HERE for a SPANISH VERSION

 

References

  1. McDaniel, N.L. (2001). "Ventricular and atrial septal defects." Pediatrics in Review, 22(265)
  2. Moore, J.W. (2013). "Less invasive technique now a standard for ASD closure."  AAP News, 23(62).
  3. Nakamura, F.F. et. al. (1964). "Atrial septal defects in infants." Pediatrics, 34(101)
  4. Univeresity of Chicago Cardiology Page


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