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What is an Atrial Septal Defect ? The two upper chambers of the heart are called the right and left atrium. They are separated by a "wall", called the ATRIAL SEPTUM. Sometimes, this "wall" is not complete. There is a HOLE in it. This hole is called an Atrial Septal Defect - or ASD, in short ! ASD's may be large or small, single or multiple. The heart may be normal in all other ways, or there may be other defects too.

Maybe a picture will make it a little clearer.

What happens when there is an ASD ? In the normal heart, blood flowing in the right sided chambers (atrium and ventricle) is completely separated from that in the left sided chambers, by the atrial septum. When there is a hole in this "wall", blood from the left atrium flows through the hole into the right side. "Why only from left to right ?" you ask. Well, that's because the pressure of blood in the left atrium is higher than the right, and as you know, any fluid, including blood, will flow from a place with high pressure to one with lower pressure.

So what is the effect of this ? The right ventricle (lower chamber) now receives blood from TWO places. The normal amount of "impure" blood coming from the veins through the right atrium reaches it. In addition, some extra blood comes through the hole in the atrial septum into the right ventricle ! So, the ventricle now has to work harder to pump this increased volume of blood into the lungs. And as a result, the lungs also receive a larger amount of blood than normal.

Too much of a good thing is NOT good ! When the lungs get more than the normal amount of blood, they become "flooded" and stiff. Breathing becomes difficult. When there is a lot of blood in the lungs, it does not flow quickly, and this causes a high risk of INFECTIONS. Children with ASD's often catch a "chest cold" - maybe even several times a month !

As time goes by, the right ventricle may become weak due to the constant hard work. Then it will "fail" to pump out the blood entering it - a condition called HEART FAILURE.

Frequent chest colds occur. If very severe, these may prevent normal growth and development of a child. Also, the lungs receive a large blood volume, and this is harmful . The blood vessels in the lung become hard and thick, and pressure inside them increases. This condition is called PULMONARY HYPERTENSION - "pulmonary" for lung, "hyper" for high, "tension" for blood-pressure ! - which is a very serious complication. Then again, the ventricle may "fail" - HEART FAILURE. Yet another complication is ARRHYTHMIA - which means an irregularity in the rhythm of the heart. Since it handles a large volume of blood, the right atrium becomes big in size. This causes a disturbance in the heart's electrical activity, causing it to beat faster - a disease called ATRIAL FIBRILLATION.

All of these problems are common in

LARGE ASD's (which is what Rebecca has)

. But what about the little ones - are they safe ? They are safer than the large ones. But there is one other problem which may occur in both large and small ASD's - PARADOXICAL EMBOLISM.

What is paradoxical embolism ? Blood flow in the veins is normally slow and sluggish, and some small clots may form. CLOTS are small pieces of hardened blood inside a vein. In a normal person, these clots may pass through the heart into the lungs. In the lungs, they are "filtered" and prevented from entering the ARTERIES along with the purified blood. When there is an ASD, however, the clot, on entering the right atrium, may pass across the ASD into the left atrium. Along with the "pure" blood, it can then pass into the arteries, and from here to the brain. In the brain, it may block a blood vessel, preventing blood flow to a part of the brain. This causes a STROKE. A stroke is an injury to the brain. It may cause weakness or paralysis of an arm or leg, or inability to speak or unconsciousness. It can be a very serious problem, sometimes. It is because of this risk of stroke that doctors advise that even small ASD's be closed, by surgery or other methods.

Should an ASD be repaired ? Most doctors (over 95% of them) would say YES. Recently, a very few cardiologists are questioning this choice, but it is a very uncertain issue. When should an ASD be closed ?

The closure should be done as soon as possible to avoid even the small risk of heart failure or paradoxic embolism. Preferably, operation is avoided in very small children.

On the other hand, in some cases, ASD's cause problems very early in life. One such is the OSTIUM PRIMUM type ASD, which usually has other defects - like mitral valve clefts - associated with it. These children may develop heart failure very soon, and need surgery, sometimes even within the first year of life.

Here is a picture of an ostium primum type ASD

How can ASD's be treated ? Closure of ASD without any treatment is a "medical curiosity". It occurs in maybe one in a thousand ASD's. Most need to be closed by doctors.

Traditionally, closure by operation has been the method that has stood the test of time. By an open heart operation, the hole in the atrial septum is stitched using a special thread made of PROLENE or POLYPROPYLENE - which is a kind of polythene. When the ASD is very large, it may have to be closed with a "patch" of material placed over it and stitched in place. This "patch" may be the patient's own tissue - the covering of the heart called PERICARDIUM is commonly used - or a synthetic material like silk cloth or dacron.

Recently, some alternative methods have been tried. These are "experimental", in the sense that their effectiveness in the long run has not been proved. The advantages with these new procedures is that they are less painful, make hospital stay shorter, and avoid a disfiguring scar of a surgical incision.

One of these is TRANS-CATHETER CLOSURE. A catheter is a special thin tube passed into the blood vessels through a small needle-stick in the groin or forearm. Through this catheter, a special device, similar to an umbrella, is passed into the heart. The "umbrella" device is pushed across the ASD and opened. The hole is now blocked by the umbrella, which is then fixed in place.

Another method makes use of the idea of MINIMALLY INVASIVE HEART SURGERY. Through 3 or 4 small "puncture" holes in the chest, specially designed instruments are passed into the chest and used to repair the ASD. These cannot not be done in infants.

What are the complications after surgery ? Surgery for ASD's is among the SAFEST operations in cardiac surgery today. There should be NO DEATHS - but then things aren't always perfect ! In most hospitals, however, the chances of death after an ASD repair are below ONE PERCENT. Major complications are also uncommon. Rarely, bleeding may be excessive, and blood transfusions are needed. Hospital stay is usually for 5 days to a week.

What about the future ? An ASD repair is probably one of the few heart operations where we are able to restore a NORMAL HEART. Most patients lead a perfectly normal life. There is no need for life-long medication after surgery. Patients can perform almost any physical activity without ill effects.


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