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Atrial Septal Defect

Atrial Septal Defect - What it is




Atrial Septal Defect (ASD) is a defect or hole in the wall separating the two upper receiving chambers (the right and left atriums) of the heart - see figure 2.1.

ASD is one of more common "hole in the heart" seen, and it can occur in isolation or in combination with other congenital heart defects. Cardiologists subclassify these defects according to their locations on the atrial septum. The secundum ASD is the more common defect to occur as an isolated lesion. It represents about 5 - 10% of all congenital heart defects seen and is more common in females than males.

Figure 2.1
On the left is a diagram of a heart with an atrial septal defect (ASD), compared to a normal heart on the right. Hover the mouse pointer over the diagram to see the description. LA - Left Atrium, RA - Right Atrium, LV - Left Ventricle, RV - Right Ventricle.

What Is the Effect of Atrial Septal Defect (ASD)?

The left atrium is normally at a higher pressure than the right atrium. The atrial septal defect allows blood to flow from the left atrium to the right atrium. The blood shunted across the ASD is re-circulated back to the lungs. As seen in figure 2.2, some red blood returning from the lungs into the right upper heart chamber (right atrium) now can flow across the ASD to mix with the blue blood, which is then re-circulated to the lungs. Compare this to the normal heart in figure 2.3, where there is no ASD and no mixing of the red and blue blood.

Figure 2.2
Blood circulation in a heart with an Atrial Septal Defect (ASD) - KKH
Figure 2.3
Blood circulation in a normal heart

Blood circulation in a heart with an ASD. Note some red blood now crosses the ASD to mix with the blue blood.

Blood circulation in a normal heart. Note that the red and blue bloods do not mix during circulation through the heart.

The effects of having "extra" blood flowing across the ASD into the right atrium and subsequently into the right ventricle and then re-circulated to the lungs are:

  • The right-sided upper heart chamber (right atrium) and right-sided lower heart chamber (right ventricle) become dilated to accommodate this extra blood volume.
  • The lungs becomes more "wet" or even become "flooded" with this extra re-circulated blood.
  • The blood pressure in the lungs increases.

The degree to which these effects occur would depend on the size of the ASD and the amount of blood that is re-circulated back to the lungs. This can range from insignificant to severe.

Atrial Septal Defect - Symptoms

Atrial Septal Defect - How to prevent?

Atrial Septal Defect - Causes and Risk Factors

Atrial Septal Defect - Preparing for surgery

Atrial Septal Defect - Post-surgery care

Atrial Septal Defect - Other Information

The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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