Harvard Health Publications

Electrophysiological Testing of the Heart

What is the test?

If you have an arrhythmia (abnormal heart rhythm), cardiologists can use an electrophysiologic study (EPS) to find out what part of the heart is causing this change in rhythm and what medicines will work best to bring that rhythm back to normal. Sometimes doctors will recommend a treatment called ablation that can be done during EPS testing. Ablation uses electricity to kill the cells in the heart muscle that seem to cause the abnormal rhythm.

How do I prepare for the test?

You will need to sign a consent form giving your doctor permission to perform this test. Tell your doctor if you have ever had an allergic reaction to lidocaine or the numbing medicine used at the dentist's office. Also tell your doctor if you have ever had an allergic reaction to any heart medicines.

Talk with your doctor ahead of time if you are taking insulin, or if you take aspirin, nonsteroidal antiinflammatory drugs, or other medicines that affect blood clotting. It may be necessary to stop or adjust the dose of these medicines before your test. Most people need to have a blood test done some time before the procedure to make sure they are not at high risk for bleeding complications.

Your doctor may tell you not to eat anything for 12 or more hours before the test. A few people require an anti-anxiety medicine, which occasionally causes nausea, and therefore some doctors prefer to have you come with an empty stomach. You might need to plan to spend the night in the hospital afterwards for recovery.

What happens when the test is performed?

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.

What risks are there from the test?

There are significant risks from this procedure. Most important, some abnormal heart rhythms (arrhythmia) can be life-threatening, and your doctors will purposefully cause you to go through a few extra episodes of arrhythmia during the testing. If your doctors recommend electrophysiologic testing, they feel that this is a risk worth taking because it will allow them to take better care of you in the future. Because you are right in the lab and attached to a monitor while you undergo the rhythm changes, it is easy for them to treat you should your arrhythmia occur and cause you symptoms.

If ablation is included in your procedure, additional risks are present because ablation intentionally causes some scarring of a small part of the heart muscle. Complications are rare, but new rhythm changes can occur. A very rare complication occurs if the ablation instrument burns a hole through the heart muscle. This causes bleeding and may require immediate surgery. There is a small chance of stroke, a need for a pacemaker, or death from this procedure. Temporary inflammation of the sac that surrounds the heart (pericarditis) may cause chest pain. After some ablation procedures, slow emptying of the stomach may be caused by damage to nerves that are near the heart.

Risks associated with the catheter placement and use of dye are present for procedures with or without ablation. Among them is bleeding from the place where the catheter was inserted. If bleeding occurs but the blood collects under the skin, it can form a large painful bruise called a hematoma. A few people are allergic to the medicines used in the procedure, and this can cause a rash or other symptoms.

Must I do anything special after the test is over?

You will need to lie flat for around six hours after this procedure. If you received anti-anxiety medicine through your IV during the procedure, you might feel sleepy at the end of the procedure and you might not remember much of the test. You should not drive or drink alcohol for the rest of the day.

Depending on what happened during your test, you might need to wear a heart monitor in the hospital for a few hours or overnight.

How long is it before the result of the test is known?

Your doctors can tell you how the testing went as soon as it is over. If you had ablation done, the results will not be certain until you have had some time to see if your arrhythmia seems to be under control after the treatment.


Disclaimer: This content should not be considered complete and should not be used in place of a call or visit to a health professional. Use of this content is subject to specific Terms of Use & Medical Disclaimers.

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