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Optical Coherence Tomography
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Related terms: OCT, optical imaging

Optical coherence tomography (OCT) is a diagnostic procedure that is used in combination with a procedure called cardiac catheterization. The technique uses near-infrared light to create images of the inside of your blood vessels. Unlike ultrasound, which uses sound waves to produce an image of the blood vessels, OCT uses light. With OCT, doctors can obtain images of the blood vessels that are about the same as if they were looking under a microscope.

How does it work?

OCT uses near-infrared light to create images of the inside of the coronary arteries. The technique delivers such high-resolution images because it uses light instead of sound waves. A beam of light is directed at the artery, and some of the light reflects from inside the artery tissue and some of it scatters. This scattered light causes something called "glare." Using OCT, the glare can be filtered out. Even the smallest amount of reflected light that is not scattered can be detected and used to form the image of the coronary artery. In fact, OCT allows cardiologists to see in 10 times more detail the inside an artery than if they were using intravascular ultrasound.  

OCT is used along with heart catheterization procedures, including angioplasty, in which cardiologists use a tiny balloon on the tip of a catheter to unblock a coronary artery. Most patients who undergo balloon angioplasty also receive a stent—a small mesh-like device placed inside the artery to keep it open. OCT images can help cardiologists see if a stent is holding an artery open and whether the stent is positioned correctly against the artery wall. OCT also lets cardiologists clearly see the plaque inside an artery, find out how much fat or clot is inside an artery, and take precise measurements before and after placing stents.

What should I expect?

Do not eat or drink anything after midnight the night before your procedure. Talk to your doctor about any medicines (prescription, over-the-counter, or supplements) that you are taking, because he or she may want you to stop taking them before the procedure. Also, it may be helpful if you make a list of the medicines and take it with you to the procedure, so that the doctors and technicians know exactly what you are taking and how much. You will most likely have blood tests, an electrocardiogram, and a chest x-ray taken before the procedure.  

Once you are in the catheterization laboratory (also called the cath lab), you will see television monitors, heart monitors, and blood pressure machines. You will lie on an examination table, which is usually near an x-ray camera.  

Electrodes will be placed on your chest. These electrodes have wires called leads, which hook up to an electrocardiogram machine. This machine will monitor your heart rhythm.  

To prevent infection, you will be shaved and cleansed around the area of your groin or arm where the catheter will be inserted.  

A needle with a tube connected to it will be put in your arm. This is called an intravenous line or IV. You will get a mild sedative through the IV to relax you.  

You will be given an anesthetic medicine with a needle to numb the area around where the catheter will be inserted. You may feel mild discomfort when the local anesthetic is given. You should not feel any further pain from this point forward in the procedure. Doctors then insert a sheath into the artery or vein. Different catheters can be inserted and removed through the sheath to perform the catheterization  

Before performing angioplasty or placing a stent, cardiologists may use OCT to create images that show where the blockages are in the coronary arteries and where to place the stent.  

After the procedure, the catheter and IV line will be removed. You will also be disconnected from the electrocardiogram machine. Firm pressure will be applied to the site where the catheter was inserted to stop any bleeding. You will also be bandaged.  

You will be moved to another room where you will need to rest for 5 or 6 hours. You may feel a little sleepy until the sedative has worn off. You will be told to lie still. If the catheter was inserted in your groin, try not to bend your knee. If the catheter was inserted in your arm, try not to bend your elbow. Nurses will watch you to see that your heart rate and blood pressure are normal. After this time of rest, you can go home.

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Updated August 2014
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