Information regarding obstruction defects of the heart - atresia, stenosis and coarctation.

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Obstruction Defects (Atresia / Coarcation / Stenosis)

Sometimes one of the heart’s valves is narrowed, blocked or missing, or the main artery to the body (aorta) is narrow. These conditions may be found in association with other defects and the problems caused will depend on where and how severe the blockage is and what the other defects are.

  • Atresia - blocked, missing or never formed
  • Coarctation - narrowing of the aorta
  • Stenosis - narrowing of a valve or blood vessel

Although rare, we have included basic information here for those who need it.

Aortic Atresia

With this condition the valve between the left ventricle (pumping chamber) and the aorta (main artery to the body) is blocked or missing and therefore blood cannot pump from the ventricle to the body, so the route the blood takes is through the ductus arteriosus (which bypasses the baby’s lungs in the womb).

Depending on the other defects found, treatment may include giving drugs to keep the ductus arteriosus from closing (as it normally does shortly after birth). The baby will require an operation to re-route the blood flow, so that the right ventricle can pump the blood to the body.

Aortic Stenosis

Here the aortic valve between the left ventricle (pumping chamber) and the aorta (main artery to the body) does not open properly. This means that the heart has to work harder than normal to pump the blood through the valve and around the body.

Treatment may be by balloon dilation by catheter to widen the valve, or if this is unsuccessful or not possible, valve surgery will be required.

Coarctation of the Aorta

This is a narrowing of the aorta (main artery) from the heart to the body. This usually is diagnosed during pregnancy or soon after birth, when the baby becomes ill. The doctors will resuscitate the baby and start a drip with prostaglandin. This will reopen the ductus arteriosus (which bypasses the baby's lungs in the womb) and allow the baby to recover. An operation will then be required to widen out the narrowed area of aorta.

Rarely, coarctation may be diagnosed in later childhood, and it may then be possible to treat it with a balloon and stent (open tube used to keep the artery open) inserted from the groin.

Mitral Atresia

This is an uncommon condition, where the left side heart valve (mitral) has not formed. The oxygenated blood from the lungs is unable to enter the left ventricle and to be pumped round the body properly. It usually mixes with the blue blood (blood which has taken oxygen around the body and is returning to the lungs to obtain more oxygen) from the body.

The diagnosis will be made as a result of too little blood going to the lungs (Blue baby) or too much (breathless baby) or both. The treatment will depend on the associated conditions.

Mitral Stenosis

This is a narrowing or obstruction of the mitral valve which is located between the left atrium and left ventricle (upper and lower chambers), which restricts the blood flow into the left ventricle (pumping chamber) and then forward to the body.

If it is severe, valve replacement will usually be necessary, in less severe cases it may be possible to repair the valve in order to widen it out and to relieve the narrowing.

Pulmonary Atresia

In this condition the pulmonary valve (between the heart and lungs) is not formed and blood cannot flow from the right ventricle (pumping chamber) to the lungs.

Initial treatment may include drugs to keep the ductus arteriosus open (this ‘shortcut’ normally closes soon after birth) to allow blood to flow to the lungs and also a balloon atrial septostomy rarely will be required to place a hole (ASD) in the central heart wall of the heart between the atria (upper chambers). Later surgery is typically done in stages starting with a Blalock-Taussig (BT) shunt, then either a staged repair to use both ventricles appropriately or a bi-directional Glenn and finally the Fontan if it is not possible to use two ventricles to pump blood to the body and lungs separately. These are all methods of diverting blood by making new connections between parts of the heart to overcome the problems caused by the missing pulmonary valve – more information on each procedure can be found by reading the Blalock, Glenn & Fontan Procedures Topic Note

Pulmonary Stenosis

Here the valve in the pulmonary artery (between the heart and lungs) is narrowed which makes the work harder for the right ventricle (pumping chamber) which pumps blood to the lungs.

Treatment is by balloon dilation via catheter where the balloon is inflated to stretch the valve and reduce the pressure on the right side of the heart.

Tricuspid Atresia

In this condition the tricuspid valve located between the right atrium and right ventricle (upper and lower chambers) is either missing or else is it is malformed and cannot open to allow blood to pass through. Because blood is unable to pass into the right ventricle (pumping chamber), it is always associated with an atrial septal defect (ASD) which allows the blood to flow from the right atrium (upper chamber) into the left one. The path it takes then depends on the other defects present, but blood flow to the lungs may be decreased and a shunt may be necessary to improve this, or it may be excessive, when a pulmonary artery band may be inserted at operation in order to limit blood flow to the lungs.

It is not usually possible to replace the tricuspid valve, but depending on the other defects, a procedure called the Fontan is used to improve the blood circulation and improve oxygen saturation levels.more information on each procedure can be found by reading the Blalock, Glenn & Fontan Procedures Topic Note

Tricuspid Stenosis

This condition is rare as a birth defect. The three leaflets of the tricuspid valve (found between the upper and lower chambers of the right side of the heart) fail to open fully restricting the flow of blood from the right atrium (receiving chamber) into the right ventricle (pumping chamber). The increased pressure in the atrium (receiving chamber) causes it to stretch. Surgery will often be required to widen the tricuspid valve or rarely to replace it.


You can find more information about balloon dilation and balloon septostomy by reading the Cardiac Catheterisation Topic Note and about valve replacement by reading the Valve Problems Topic Note


A list of reference sources used for this publication can be viewed on our website at or you may call to request details in print.


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