Pulmonary Stenosis – PS
Pulmonary Stenosis (PS) is one of the simpler abnormalities of the heart. But even this requires some basic knowledge about the structure of the heart.
What is Pulmonary Stenosis ?
The word “pulmonary” denotes “to do with the lungs”.
The pulmonary valve is located between the right ventricle and the pulmonary artery. It regulates blood flow into the lungs, and prevents blood from leaking back into the right ventricle.
Sometimes, this pulmonary valve is extremely narrow, and blocks the smooth flow of blood into the lungs. This condition is called Pulmonary Stenosis – or PS, in short.
At other times, the pulmonary valve itself is normal, but there is an obstruction to blood flow from the right ventricle at other levels. For instance, there may be abnormal bundles of muscle below the pulmonary valve which obstruct flow. This is called “sub-valvular” pulmonary stenosis.
Or occasionally, there may be a narrowing of the pulmonary artery or its branches above the pulmonary valve. This is called “supra-valvular” pulmonary stenosis.
What happens in PS ?
I have emphasized in earlier discussions the importance of blood flow to the lungs. The lungs are the only organs in the body where blood can be purified by the addition of oxygen, and removal of waste materials, like carbon-dioxide. This oxygen containing blood is distributed to the rest of the body. Without oxygen for energy, the other organs cannot carry out their normal work.
In PS, blood flow to the lungs is reduced. So the amount of blood getting oxygenated is less than normal. In patients who have very slight narrowing, there is not much effect. But when the block becomes severe, symptoms begin. Usually children with pulmonary stenosis have a limited tolerance to exercise. They become tired easily at play, and have to rest.
Rarely, giddiness and fainting may occur. Some children complain of palpitations – which is an uncomfortable awareness of their own heart-beat. In very severe PS, there may be mild cyanosis – a bluish discoloration of the body. The cyanosis is caused by veno-arterial mixing across the wall between the right and left atrium.
The diagnosis usually is obvious on medical examination. Confirmation may be obtained by tests like echocardiography, or sometimes by cardiac catheterization.
What needs to be done for PS ?
In PS, the smooth flow of blood into the lungs is obstructed. This needs to be relieved. In the early stages of the disease, not many effects are seen. But if left untreated for many years, it may cause problems.
The right ventricle, which pumps blood into the lungs, is now forced to work harder against the blocked pulmonary valve. To do this, the right ventricle wall becomes thicker by addition of more muscle – a condition called “hypertrophy“.
But even the stronger right ventricle cannot keep up this hard work forever. Finally, it “fails” to pump blood effectively, producing sudden worsening of symptoms. At this stage, urgent treatment becomes necessary, and carries a higher risk.
So although PS is usually not an emergency, it is advisable to seek treatment early rather than delaying the process till complications set in.
What are the options for treating PS ?
For many years surgery has been the only effective treatment for PS. But with the arrival on the scene of catheter-based therapy, it has today virtually taken-over the treatment of PS.
Trans-Catheter Balloon dilatation is effective in most cases, and has lesser morbidity than surgery.
What is Balloon Pulmonary Valvotomy ?
Balloon Pulmonary Valvotomy – or BPV – is a catheter based treatment for PS.
A “catheter” is a thin plastic tube that can be threaded through the arteries into the heart itself. The catheter is introduced through a small needle-stick in the groin or forearm and guided into the heart.
In Pulmonary Stenosis the catheter is passed into the right atrium, then into the right ventricle across the tricuspid valve, and finally guided across the narrow pulmonary valve.
The specially designed “balloon catheter” has a device similar to a balloon positioned at the tip of the catheter. This balloon is positioned just across the narrow pulmonary valve, and then inflated. The blown-up balloon “opens up” the narrow pulmonary valve, relieving the block!
Simple, isn’t it?
How effective is BPV?
BPV has become a very effective treatment for PS, almost making surgery for PS obsolete. When the narrowing is only at the pulmonary valve, there is almost complete relief of stenosis. And it avoids the drawbacks of surgery – pain, a scar on the chest, long in-hospital stay, and higher cost.
If however additional narrow areas are present either above or below the pulmonary valve, the results may not be quite as good. One of the dangers of BPV is that it may “tear” the pulmonary valve, and make it “leaky” – Pulmonary Regurgitation.
This however is very rare. And even if it occurs, it does not cause much problem immediately because the pressures on the right side of the heart are very much lower than the left side.
What about surgery – Does it have a role at all ?
Certainly. Though at the rate these “catheter-pushers” are going, we “scalpel-wielders” may soon be out of business!
Most cases of PS due to pulmonary valve narrowing are candidates for BPV. But when BPV is not possible due to non-availability or lack of experience, surgery may be needed. Also, when other conditions co-exist it may be better to offer surgery to correct all defects at one sitting.
What operations are performed for PS ?
The common procedure is called Open Pulmonary Valvotomy (OPV). This is an “open-heart” operation, and is done after the patient is hooked up to a heart-lung machine. The pulmonary artery is opened, and the narrow pulmonary valve examined. Usually, the leaflets of the pulmonary valve are stuck to the wall of the pulmonary artery – “tethering” – and to one another along well-defined lines – “cuspal fusion”. The valve is opened-up by dividing its leaflets along the lines of attachment using a scalpel.
Additional sites of block are sought. If there is an obstruction below the valve due to abnormal muscle bundles, these are divided and removed. If the pulmonary artery or its branches are narrow, they are widened by using a patch of pericardium to increase their size – similar to the repair used in Tetralogy of Fallot.
Sometimes the valve may be extremely narrow and this alone is not enough. In such cases, a Trans-Annular Patch repair may be indicated. In this repair, a cut is made across the narrow area, and the opened up portion is roofed using a patch of pericardium or synthetic fabric.
What are the risks of surgery ?
Surgery for PS is relatively safe. The complication rate is very low, and includes those common for any open-heart operation. This includes bleeding needing blood transfusions and rhythm disturbances – arrhythmia.
Sometimes the relief of obstruction may be incomplete due to technical problems. Most types of PS however can be effectively relieved by operation. Also, any additional defects can be treated at the same time.
What about the long term effects ?
Most patients operated for pulmonary stenosis go on to lead normal lives. The risk of late complications is very low. In most children, as growth occurs, the pulmonary valve also becomes larger, and this itself reduces the stenosis to some extent.
The potential problems are rhythm disturbances and “late” pulmonary valve leak due to injury at the time of operation.