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What is Cardiac catheterization?
This is a medical test which enables the cardiologist to see the various heart chambers and blood vessels.  A long, flexible and slender tube (which looks very much like an electrical wire, except that it is hollow), called catheter, is used to perform this test.  The catheter is introduced through a needle into a large vessel, usually in the groin, and is pushed towards the heart.  The motion of the catheter is seen through an x-ray camera connected to a monitor displaying the catheter.  The x-ray camera produces images similar to a chest x-ray, the heart appears as a white shadow, but its various structures are not identified.  The catheter is designed such that it could be clearly seen.  Once the tip of the catheter reaches the heart, it could be manipulated into various cardiac chambers and vessels. 

 

What information could be obtained from cardiac catheterization?
Pressures:   The pressures of blood  inside various heart chambers and blood vessels could be measured.
Presence of shunt lesions:  Samples of blood is obtained form the different chambers and vessels to measure oxygen saturation.  This would detect any holes in the heart which allow blood with high oxygen concentration to cross over to the right side of the heart and cause its normally low oxygen contents to be higher.
Visualize cardiac structures:   A dye (contrast material) is injected inside a heart chamber or vessel which fills the space, thus providing an image of the structure and how it moves during the heart cycle, this is called angiography.

 

The numbers within the cardiac chambers and vessels is an example of  the pressures obtained through the catheter in mmHg (millimeters of mercury).  The left heart chambers have higher pressures than the right heart chambers.

 

The numbers within the cardiac chambers and vessels is an example of  the oxygen saturation.  A sample of blood is obtained and oxygen saturation's measured.  The left heart has normally high oxygen saturation, while the right heart chambers have lower saturation.

 

By injecting a coloring dye in a heart chamber (the right ventricle (RV) in this case), the chambers and vessels of the heart could be seen.

 

A Case Demonstration
To demonstrate the usefulness of cardiac catheterization, the following is a case in which cardiac catheterization was helpful in many ways.
A one yea old child with a heart murmur was found by echocardiography to have severe pulmonary stenosis (significant obstruction of blood outflow through the pulmonary valve).   In the cardiac catheterization laboratory the pressure in the right ventricle was measured.  As expected it was severely elevated:  80 mmHg (normal is about 20-25 mmHg), see image below.  To demonstrate the abnormal valve a coloring dye was injected in the right ventricle and an x-ray film was shot.  Indeed this showed an abnormally thickened and poorly opening valve, again supporting the diagnosis of pulmonary stenosis as obtained from echocardiography, see image & movie clip below.   The diameter of the pulmonary valve was measured and a suitable size balloon catheter was selected.  These catheters have an inflatable balloon at its end which is put across the narrow valve and the balloon is inflated which causes relief of obstruction, see image & movie clip below.  

QuickTime software needed to view the movie clips below.
To download free software clock here.

 

The pressure in the right ventricle increase with pulmonary stenosis, here it measured 80 mmHg, four times the normal pressure.

 

The coloring dye filling the right ventricle.  The pulmonary valve is thick and the jet of blood (mixed with the dye) is seen, this is much narrower than normal, due to the abnormally small opening of the valve.
Click on the image to view a movie clip of the angiogram.

 

 

 

A balloon attached to a catheter is put across the pulmonary valve is inflated, thus enlarging the opening of the pulmonary valve, thus reducing obstruction.
Click on the image to view a movie clip of the angiogram.
The pulmonary valve now opens better and the blood is able to be ejected more easily through the pulmonary valve.
Click on the image to view a movie clip of the angiogram.
 
Therapeutic Cardiac catheterization
Obtaining information about the heart in the cardiac catheterization laboratory was the only use for this procedure one decade ago.  Over the past several years cardiac catheterization has been increasingly used for purpose of treating heart diseases as demonstrated in the example above.   Many different procedures could be performed in the catheterization laboratory.  This includes:

1.  Relieving obstruction at valves such as pulmonary and aortic stenosis.
2.  Occluding abnormal communications, such closing an atrial septal defect or a patent ductus arteriosus.
3.  Making a small atrial communication bigger as may be needed as a temporary measure in certain congenital heart disease, this is known as Rashkind atrial septostomy.

The catheter has an inflatable balloon at its end.  Once across the pulmonary valve, the balloon is transiently inflated causing the valve leaflets to open wide, thus relieving stenosis.

A special wire is advanced through the aortic valve and into the left ventricle, then a catheter with an inflatable balloon is advanced over the wire until it crosses the aortic valve, the balloon is then transiently inflated causing the fused valve cusps to separate from each other resulting in a larger opening of the valve.

In the cath. lab, a catheter is introduced through the femoral artery (from the groin) and advanced into the aortic arch, then across the PDA and into the pulmonary artery.  At the pulmonary artery end of the PDA a coil is extruded from the catheter which loops and occludes the ductus arteriosus.

In this procedure a catheter is inserted in the femoral vein (in the groin) and advanced to the heart.  In the heart this special catheter crosses the ASD into the left atrium.  While at the left atrial side of the ASD a device is extruded out of the catheter, which once gets out of the catheter tip opens up into a mushroom shaped object which when pulled back against the atrial septum will occlude the hole.  The catheter is then pulled further back into the right atrium and the other part of the device will extrude out of the catheter which would close the hole in the atrial septum from the right atrial side as it comes close to the first component of this device.

In many diseases, such as pulmonary atresia and transposition of the great arteries, a small atrial communication (ASD) is detrimental to life.  Therefore, a small ASD could be made larger by a special catheter with an inflatable balloon at its tip when put across the ASD into the left atrium, the balloon is inflated and the catheter is briskly pulled back into the right atrium causing a tear in the atrial septum, thus enlarging the ASD.  This hole could be later repaired when it is time to repair the heart lesion.