What is Atrial Septal Defect - ASD

Atrial septal defect (ASD) is a congenital heart defect. In fetal circulation there is normally an opening between the two atria (the upper chambers of the heart) to allow blood to bypass the lungs. This opening usually closes about the time the baby is born. If the opening is persistent it is called an ASD, and thus blood continues to bypass the lungs. This is called a shunt.

Atrial Septal Defect - ASD (Paediatric Cardiology)

Who gets Atrial Septal Defect - ASD?

About 1 in 2000 live births.

Predisposing Factors

The aetiology of congenital heart defects is not understood but several factors are known to be associated:

1) Maternal drug abuse, alcohol abuse and radiation exposure.

2) Maternal infection, particularly rubella.

3) Genetic abnormalities.

4) Chromosomal abnormalities (septal defects are associated with Trisomy 21- Down’s syndrome).

Progression

ASDs may occur in isolation or may be associated with other malformations:

* Spontaneous closure of ASDs is rare after the first 2 years of life.
* ASDs allow shunting of blood from one side of the circulation to the other. There are no great pressure differentials across the two atria and shunting is usually from left to right due to the greater compliance of the right heart chambers. Flow rates across the defect are usually not high2.
* Increased flow to the pulmonary circulation eventually leads to pulmonary hypertension, usually by the 4th decade. Atrial arrhythmias, particularly AF are common due to the physical distention of the atria5.
* In severe cases the shunt can eventually reverse so that blood bypasses the lungs - this is termed Eisenmenger’s syndrome and is a poor prognostic factor2.

Probable Outcomes

Most commonly symptoms dont develop until the twenties when evidence of pulmonary vascular disease becomes apparent. With increasing age, risk of developing cardiac rhythm disturbances increases. By the age of 40 most patients are severely symptomatic.

Cardiac failure is the most common cause of death. Others include emboli and infections.

How is Atrial Septal Defect - ASD Diagnosed?

Chest x-ray: Prominent pulmonary vasculature may be seen. Right ventricular hypertrophy may be seen.
ECG: May show some right bundle branch block and right axis deviation.

How is Atrial Septal Defect - ASD treated?

Large ASDs (where pulmonary blood flow is greater than 150% normal) should be repaired surgically as early as possible, preferably before 10 years. The outlook is good if pulmonary hypertension (high blood pressure in the lungs) has not developed.

Otherwise, medical management of heart failure and other complications such as arrhythmias should be instigated.

Atrial Septal Defect - ASD References

[1] Anderson et al. Paediatric Cardiology. Churchill Livingstone 1987.
[2] Behrman, Kliegman, Jenson. Nelson Textbook of Paediatrics 17th Ed. Saunders 2004.
[3] Hurst’s The Heart 8th Edition, McGRAW-HILL 1994.
[4] Kumar and Clark Clinical Medicine 4th Edition, W.B SAUNDERS 1998.
[5] Rudolph et al. Rudolphs’s Paediatrics (21st edition). McGraw-Hill 2003.

What is Ventricular Septal Defect

Ventricular Septal Defect (VSD) is a disease of the heart, namely the septum (or division) between the two ventricles (or main chambers of the heart).

Ventricular Septal Defect (VSD)

Who gets Ventricular Septal Defect?

3-4 per 1000 live births. VSD is the most common congenital cardiac malformation.

Predisposing Factors

The aetiology (origins) of congenital heart defects is not understood but several factors are known to be associated with this condition:

1) Maternal drug abuse, alcohol abuse and radiation exposure.
2) Maternal infection during pregnancy, particularly rubella.
3) Genetic abnormalities.
4) Chromosomal abnormalities (septal defects common with Trisomy 21- Down’s syndrome).

Progression

VSDs may occur in isolation or may be associated with other malformations. Small VSDs usually close spontaneously.

Moderate to large VSDs often become smaller but remain patent and allow shunting of blood from one side of the circulation to the other. Because the left (systemic) blood pressure is higher than the right (pulmonary), the shunt is left to right and increased blood is circulated through the lungs.

Eventually, the increased flow rates through the pulmonary circulation lead to obliteration of the lung tissue and pulmonary hypertension. When the pulmonary circulatory pressure is equal to or greater than the systemic, the shunt reverses and becomes right to left. This is called “Eisenmenger’s syndrome.” When this occurs, less blood flows through the pulmonary circulation and the patient may become cyanosed (skin and mucous membranes turn blue) as a result of poor blood oxygenation.
Ventricular septal defects are rarely “acquired,” as in myocardial infarction involving the ventricular septum.

Probable Outcomes

Approximately 24% of small defects close spontaneously by 18 months. Up to 75% are closed by the age of 10. Large septal defects threaten life early on through congestive failure. The risk of death is 11%. If large defects are not corrected before pulmonary hypertension develops the outlook is poor. Patients with the Eisenmenger’s syndrome have an average life expectancy of 33 years. Fortunately surgical techniques may provide a better outcome.

How is Ventricular Septal Defect Diagnosed?

Chest x-ray: small VSDs may show nothing. Moderate may show cardiomegaly and enlarged pulmonary arteries due to increased pulmonary vascular flow rates.
ECG: features of right ventricular enlargement may be seen.

How is Ventricular Septal Defect treated?

For small defects medical treatment may be tried (eg. treating heart failure) if the defect is expected to improve spontaneously. Frequent measurement
of pulmonary pressure should be performed to monitor this condition.

Moderate to large defects should be corrected surgically.

Ventricular Septal Defect References

[1] Anderson et al. Paediatric Cardiology. Churchill Livingstone 1987.
[2] Behrman, Kliegman, Jenson. Nelson Textbook of Paediatrics 17th Ed. Saunders 2004.
[3] Hurst’s The Heart 8th Edition, McGraw-Hill 1994.
[4] Kumar and Clark, Clinical Medicine 4th Edition, W.B SAUNDERS 1998.
[5] Rudolph et al. Rudolphs’s Paediatrics (21st edition). McGraw-Hill 2003.