Ventricular Septal Defect – VSD

What is a Ventricular Septal Defect?

Ventricular septal defects – also called VSD – are similar to ASD.

A VSD is a “hole” in the wall between the two lower chambers of the heart – the ventricles.

VSD may be small, medium-sized or large, and may be single or multiple. It may occur in different parts of the ventricular septum, and may sometimes be found along with other heart defects.

What happens when there is a VSD ?

The wall between ventricles is meant to separate blood passing through each. This is to prevent mixing of “impure” blood from the veins with “pure” blood going to the arteries. When the wall is “broken”, mixing occurs.

However, only “pure” blood flows from the left ventricle into the right; no flow is seen from the right ventricle into the left side across the VSD and so “impure” venous blood does not reach the arteries. This is because pressure in the left ventricle is much higher than the right, and fluids always flow from places of high to lower pressure.

Because of this flow from left to right ventricle across the VSD – also called a LEFT to RIGHT SHUNT – more blood than normal flows into the lungs. Just as in atrial septal defects (ASD), this causes frequent “chest colds” and breathing difficulty in children.

When the VSD is large, in a very small child, lung blood flow may be so enormous that the tiny ventricles cannot pump such a volume. This causes Heart Failure. Heart failure in a child produces rapid shallow breathing, excessive sweating, inability to feed well, irritability, constant crying, and a failure to grow normally.

Have you felt a kitten purring ? Well, here’s something interesting about these children with VSD. When you place your palm over their chest, there is a sensation just like that – called a thrill. It is produced by the forceful and turbulent flow of blood across the VSD.

One effect seen in VSD – but not in ASD – is the rapid development of abnormal changes in the blood vessels of the lungs. The arteries and veins in the lung become thick walled and hard rather early in life. The reason for this is perhaps because blood from the left ventricle, which is the most powerful chamber of the heart, is pumped under high pressure across the VSD into the lungs. To withstand such force, the tubes carrying blood become thick and strong.

What happens if VSD’s are left untreated ?

The changes I have just described keep progressing. Soon the heart fails to keep up with the high blood flow, and heart failure sets in. When the lung blood vessels become very thick, the problem of Pulmonary Hypertension arises. This is a situation where the lung arteries are severely damaged, and at this stage, even surgical repair of the VSD will not be able to cure the disease.

When the VSD is located in the upper part of the inter-ventricular wall, close to the aortic valve, it can slowly make the aortic valve “leaky” – a condition called Aortic Regurgitation. This usually takes many years.

In small VSD’s, these effects are uncommon. But there is one complication peculiar to a small VSD – Infective Endocarditis. Due to a turbulent jet of blood across the VSD, the inner lining of the heart – endothelium – gets disrupted. Bacteria can stick to this injured area, and cause an infection inside the heart.

VSD along with other defects

VSD may be found alone, as the only defect in a heart that is otherwise normal. Or it may form a part of a “complex” of abnormalities. In this case, it may produce different effects. Some examples of such diseases are Tetralogy of Fallot, Transposition of Great Arteries and Double Outlet Right Ventricle.

To avoid confusion, I will describe these conditions separately in other articles.

On what basis are VSD classified as large and small ?

There are many ways of classifying VSD. While a VSD might be described as being 8 mm. in diameter, this is rather imprecise. An 8 mm. defect in an adult might be considered “small” while in an infant, it would be “large”. The most practical approach is comparing its size to the patient’s aortic valve. A VSD which is larger than one-half of the aortic valve orifice is considered “significant” or large.

Should a VSD be repaired ?

There is not much doubt about the need for closure in a large VSD where the patient usually has severe symptoms due to heart failure. But the decision is not always easy.

There is another special thing about VSD. Some of them close even without any treatment!

There is no way to definitely and reliably predict which VSD will close and which will not. The best chance for closure is in the first six months of life. After this, spontaneous closure becomes less frequent. If by the tenth year of life the VSD has not closed by itself, it probably needs to be repaired.

There is one exception to this rule – the Small VSD. There is still much controversy about this problem. While surgeons advise that small VSD’s be repaired, cardiologists sometimes recommend “no treatment”. The arguments against repair are the small risk and discomfort involved with surgery, and the absence of any symptoms in most patients. The surgeons however claim that

  • repair is safe and has very few complications
  • all chances of future effects, particularly infective endocarditis, are avoided
  • the child and parent are freed of the “psychologic” stigma of heart disease
  • life and health insurance issues arise in some countries

The decision to repair these small defects would perhaps depend on the hospital, and the philosophies of the parent and the doctor.

When should a VSD be repaired ?

This is another area where decision making is very complex. Factors to be considered are the age of the patient, size and location of the VSD, severity of lung vessel blood pressure and the degree of symptoms of heart disease.

In very small babies with severe heart failure and large VSD, immediate repair usually cannot be avoided. If there is no heart failure, however, surgery can be postponed until SIX MONTHS of age. The reason for this is that a certain number of VSD will close spontaneously by this age.

Beyond six months, the decision to close a VSD is based on measurement of Pulmonary Vascular Resistance – that is, the degree of damage to lung blood vessels. If the damage is not too severe, closure is strongly recommended. If the damage is severe, repair of the VSD may actually be harmful. These patients have crossed the boundary of “operability”.

With medium-sized VSD’s, a longer waiting period is possible. If even after five to ten years the VSD has not closed, repair is justified. A special group is the VSD’s that are just below the aortic valve. Because of the risk of the valve becoming “leaky” in these patients, earlier repair – before five years – is better.

NOTE: A lot of controversy still surrounds issues related to closure of VSD. The facts I have mentioned above are only currently “accepted guidelines”. The decision about which treatment option is best for a particular case is best made by the physician who analyzes all the factors.

What are the ways to close VSD’s ?

Surgical closure by an open heart operation is the “tried and tested” approach for VSD. The surgeon may close the VSD by opening the right atrium or ventricle, or maybe even only the pulmonary artery or aorta.

Rarely, when multiple VSD’s are present – the so-called Swiss Cheese Ventricular Septal Defect – an access through the left ventricle is preferred.

In small VSD, simple closure of the hole with sutures made of polypropylene or similar material is enough. When the defect is large, a synthetic “patch” made of a fabric like dacron or PTFE (Poly tetra-fluoro ethylene) is used. Interestingly, some surgeons have used a kind of “glue” to simply plug any holes in the ventricular septum, but this technique is still experimental.

This is the era of “minimal access repair”. In keeping with this trend, the “catheter-pushers” (or Interventional Cardiologists, if you prefer that term) have developed a way to close VSD using catheters.

Through a narrow plastic tube – called a catheter – threaded into an artery by a “needle-stick” in the groin or fore-arm, a special device – called a “clam-shell device” – is guided into the heart. This umbrella-like device is passed across the VSD and opened. The umbrella closes the VSD, and it is fixed in place.

Though elegant, this method is still under evaluation. If found equally effective, this may be an alternative to surgery in closure of small VSD’s.

Is VSD repair absolutely safe ?

Not absolutely, but yes, it is reasonably safe. Life isn’t perfect after all! Most complications are not serious. There may be excessive bleeding requiring a blood transfusion. Infection may occur and be treated by medicines. The mortality risk is very low, and in most hospitals will be below 2%, except in very sick patients with a large VSD and other defects.

There is however one problem that used to be seen often in older times, but which still may happen. This is an arrhythmia called Heart Block.

What is heart block ?

A weak electrical current is normally produced inside the heart, and it follows a definite pathway as it excites the heart muscle and stimulates it to contract. This path is marked out by conduction tissue – a special kind of cell designed to “conduct” or carry current. The conduction tissue of the heart passes very CLOSE to the margins of some VSD’s.

When stitches to repair the VSD are applied, they may injure this conduction tissue. As a result, electric impulses will not be carried normally, and will get “blocked”. This is called heart block. In some cases, it will recover naturally within a short period.

But in some it does not, and needs implantation of an artificial pacemaker – a device that delivers an electric current and sets the “pace” of the heart.

How does the “VSD-repaired” patient do in the long run ?

Fortunately, very well. Most children lead normal lifestyles. Very few restrictions apply.

For instance, if they have had surgery through an incision through the middle of the chest, that has split the breast-bone, they are limited from playing rough contact sports for fear of fracture.

If a synthetic “patch” has been used to close the VSD, some medicines may need to be taken for the first few weeks after operation to prevent blood clotting on the patch. Even later on, before other minor operations or medical tests – like having dental work or a tooth extraction – some medicines called antibiotics may need to be taken for a day or two, to decrease the risk of infection on the patch.

During any illness in the future, don’t forget to mention to the doctor that a patient has had operation for a VSD. Otherwise, VSD-repaired patients have an almost normal life.

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