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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

What Happens During the Test?

The test is done by a specialist using equipment and cameras in the cardiology department. You wear a hospital gown and lie on your back during the procedure. You have an IV (intravenous) line placed in a vein in case you need medicines or fluid during the procedure. Your heart is monitored during the test.

A catheter (a hollow, sterile tube that resembles spaghetti) is inserted through the skin into a blood vessel-typically in your groin, but possibly in the neck or arm. Before the catheter is placed, medicine through a small needle is used to numb the skin and the tissue underneath the skin in that area. The numbing medicine usually stings for a second. A needle on a syringe is then inserted, and some blood is drawn into the syringe, so that the doctor knows exactly where the blood vessel is located. One end of a wire (but not the whole wire) is threaded into the blood vessel through the needle. The needle is then pulled out off of the back end of the wire, leaving the wire temporarily in place. This wire is several feet long, but only a small part of it is inside your blood vessel. The catheter can then be slipped over the outside end of the wire and moved forward along it like a long bead on a string, until it is in place with one end inside the blood vessel. The wire is pulled out of the catheter, leaving the catheter in place. Now the catheter can be moved easily forwards and backwards inside your blood vessel by the doctor, who holds the outside end of the catheter while using special controls to point the tip of the catheter in different directions. The doctor carefully moves the catheter to the large blood vessels in your chest and into the chambers of your heart.

As your physician maneuvers the catheter, he or she watches a live video x-ray to know exactly where the catheter is. Instruments on the tip of the catheter allow it to sense electrical patterns from your heart and also to deliver small electrical shocks to the heart muscle (or a stronger electrical burn if you are having ablation). The electrical shocks, too small for you to feel, are used to "tickle" the heart muscle in different places to see if your abnormal rhythm is triggered by one sensitive area of your heart. If the rhythm changes, your doctor gives you small doses of different medicines through this catheter to see which ones work best to change the rhythm back to normal. In some cases the doctor may need to give your heart some additional mild shocks to get it back into a normal rhythm. Because this catheter is in place inside your heart and can give the shocks directly to the heart muscle, very small amounts of electricity are used.

After the catheter has been pulled out, a pressure bandage (basically a thick lump of gauze) is taped tightly to your groin to reduce bleeding. The test usually requires one to two hours to perform.

Many patients are able to feel palpitations (an irregular or fast heartbeat) from the rhythm changes. A few patients also experience shortness of breath or dizziness when they are not in a normal heart rhythm. Other than the brief sting of the numbing medicine and some soreness in your groin area afterward, you are not likely to feel any pain. For some people, the procedure provokes anxiety. Some patients also have a difficult time lying still for the time it takes to perform this test.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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