ATRIAL SEPTAL DEFECT (ASD)

 

What is Atrial Septal Defect (ASD)?
Normal anatomy of the heart: The normal heart consists of 4 chambers - the right & left atrium (These are the chambers that receive the blood - the right atrium receives impure blood from the rest of the body and left atrium receives pure blood from the lungs.) and the right & left ventricles (These are the chambers that pump the blood from the heart – right ventricle receives blood from right atrium and pumps the impure blood to the lungs via the pulmonary artery and left ventricle receives pure blood from the left atrium and pumps the pure blood to the rest of the body via another artery called as the aorta). The impure blood in the right atrium is separated from pure blood in the left atrium by the atrial septum. A hole in this septum leads to blood flow from left atrium to the right atrium. This is because the pressure of blood in left atrium is higher than that of the right atrium.

What happens in an ASD?
As the right atrium receives blood from 2 places- impure blood from rest of the body and pure blood from left atrium, more blood reaches the right ventricle. The ventricle now has to pump harder to send this increased amount of blood into the lungs. As a result extra blood flows into the lungs than it normally does. This extra blood flow in the lungs can cause frequent chest infections. On chronic high blood flow, the blood vessels in the lungs become hard and thick leading to high pressure in the pulmonary vessels. This condition is called pulmonary hypertension. Subsequently the heart may also fail as the right ventricle may become weak due to constant hard work. These changes take many years to develop.
Another problem with ASD is arrhythmia (irregular rhythm of the heart). This occurs as the right atrium enlarges in size due to increased blood volume. That causes a disturbance in the heart's electrical activity causing it to beat faster leading to a condition called as Atrial Fibrillation. All these changes are seen with large ASD.
Many children with small ASD are not even symptomatic till they are in their 30’s or 40’s.
Sometimes clots may enter the right atrium and pass through the ASD into left atrium which then passes into the aorta and to the brain leading to a stroke – phenomenon known as paradoxical embolization. (Blood flow in the veins is sluggish and some clots may form. In a normal person, the clots pass from the right atrium to the lungs where they are filtered and prevented from entering into the pure blood). It is because of this risk, that even a small ASD needs to be closed.

How is ASD diagnosed?
ASD is suspected on clinical examination by fixed splitting of the second heart sound and confirmed by echocardiography (ultrasound of the heart).

Should an ASD be closed?
Yes. Most ASD require to be closed. Sometimes a small ASD such as a stretched PFO may be left untouched.

When should an ASD be closed?
Most children with ASD are totally asymptomatic and the ASD is detected on routine check-up. Although there is no urgency, ASD should be closed as soon as possible to avoid the risk of heart failure or paradoxical embolism.
Patients with associated heart defects such as PAPVC [Partial Anomalous Pulmonary Venous Circulation- a defect where the pulmonary veins instead of carrying the pure blood from lungs to the left atrium connect to the right atrium], Mitral valve clefts or VSD [Ventricular septal defects - Hole in the septum between both the ventricles] need to be operated early in life as these children develop heart failure soon.

How is ASD treated?
Surgery:

  • Open-heart operation- The defect in the atrial septum is stitched using a special thread. In case the ASD is large, it is closed with a “ Patch” stitched in place. This patch is usually of the patient’s own tissue such as the pericardium (the covering of the heart) or synthetic material such as silk cloth or Dacron.
  • Minimally invasive Heart Surgery- Through 3 or 4 small holes in the chest, specially designed instruments are passed in to the chest and used to repair ASD.
Interventional transcatheter closure: A catheter is passed into the blood vessel in the groin or the forearm and threaded into the heart. Through this catheter a special umbrella device is pushed across the ASD and opened. The umbrella which is fixed in place now blocks the hole.
Depending on a particular patient, the treating physician can decide which is the best procedure for closure of ASD for that patient.
After surgery, hospital stay is usually 5 to 7 days while with catheter based & minimal invasion methods, the patient is discharged in a couple of days.

Are there any complications of ASD closure?
ASD surgery is a safe procedure. Risk of death after ASD repair is below 1% and major complication are rare. Rarely, bleeding may be excessive.

Are there any problems post repair?
Patients return to a normal and productive life. There is no need for long-term medications and complications are rare depending on the degree of pulmonary hypertension prior to surgery.

 

Last created on 6-05-2003
Last updated on 18-11-2006

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