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Electrophysiology (EP) Study

Test Overview

An electrophysiology study, or EP study, is a test to see if there is a problem with your heartbeat (heart rhythm) and to find out how to fix it.

In this test, the doctor inserts flexible tubes called catheters into blood vessels. These blood vessels are typically in the groin or neck. Then the doctor threads these catheters into the heart. At the tip of these catheters are electrodes, which are small pieces of metal that conduct electricity. The electrodes collect information about your heart's electrical activity. Your doctor can tell what kind of heart rhythm problems you have and where those problems are.

Sometimes the problem can be fixed at the same time. A procedure called catheter ablation uses the catheters to destroy (ablate) small areas of your heart that are causing the problem.

Why It Is Done

An electrophysiology study is used to check your heart's electrical system. For example, it may be done to:

  • Identify heart rhythm problems.
  • Check your heart before you have an ICD (implantable cardioverter-defibrillator) implanted.
  • Treat certain problems with catheter ablation.

How To Prepare

Procedures can be stressful. This information will help you understand what you can expect. And it will help you safely prepare for your procedure.

Preparing for the procedure

  • Follow the instructions exactly about when to stop eating and drinking. This may be a few hours before the test. If your doctor told you to take your medicines on the day of the procedure, take them with only a sip of water.
  • Follow your doctor's instructions about when to bathe or shower before your procedure. Do not apply lotions, perfumes, deodorants, or nail polish.
  • Be sure you have someone to take you home. Anesthesia and pain medicine will make it unsafe for you to drive or get home on your own.
  • Understand exactly what procedure is planned, along with the risks, benefits, and other options.
  • Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your procedure. Your doctor will tell you if you should stop taking any of them before the procedure and how soon to do it.
  • If you take aspirin or some other blood thinner, ask your doctor if you should stop taking it before your procedure. Make sure that you understand exactly what your doctor wants you to do. These medicines increase the risk of bleeding.
  • Make sure your doctor and the hospital have a copy of your advance directive. If you don't have one, you may want to prepare one. It lets others know your health care wishes. It's a good thing to have before any type of surgery or procedure.

How It Is Done

Before the test

  • Be sure to empty your bladder completely just before the test.
  • You will be taken to a special room, sometimes called a "cath lab" or "EP lab." You will lie on a flat table under a large X-ray machine.
  • Several small electrodes will be placed on the skin of your chest, legs, and arms. These are connected to an EKG machine that keeps track of the electrical activity of your heart during the test.
  • A device called a pulse oximeter may be clipped to your finger. It measures oxygen levels in your blood and monitors your pulse.
  • An intravenous (I.V.) needle will be inserted into a vein in one of your arms to give you fluids or medicine during the test.
  • You will be kept comfortable and safe by your anesthesia provider. You may be asleep during the test. Or you may get medicine that relaxes you or puts you in a light sleep. The areas where the catheters will go into blood vessels will be numb. If you are awake during the test, the medicine may make you so sleepy that you may not remember much afterward.
  • The areas where the doctor plans to insert a catheter will be shaved and cleaned. This is usually in your groin, neck, or arm. Sterile towels will be draped over your body, except for the areas over the insertion sites.

During the test

  • A doctor called a cardiac electrophysiologist inserts the catheter through your skin and into the blood vessel.
  • The doctor slowly pushes the catheter through the blood vessel toward your heart. Usually several catheters are used. The doctor moves the catheters into various places in the heart. An X-ray screen shows the doctor where to move the catheters.
  • The catheters have small electrical conductors, called electrodes, on their ends. The doctor can use the electrodes to do what is called "pacing." This means sending electrical currents through the catheters to try to re-create your heart rhythm problem. This can tell the doctor what kind of problem you have and the best way to treat it. The doctor may also use pacing to see how well medicines work to control your problem.
  • The electrodes also send information to a computer. The computer uses the information to draw pictures of your heart and its rhythm problems. This is called "mapping," because the pictures serve as maps that show the doctor exactly where the problem areas are.
  • The doctor might give you a medicine through the IV that starts the abnormal heart rhythm. You might feel your heart beat fast and strong. You might also feel jittery or very nervous.
  • Your doctor may let you watch the video monitor so you can see the pictures of your heart.

After the test

  • After the procedure, pressure may be applied to the areas where a catheter was put into a blood vessel. This will help prevent bleeding and allow your blood vessels to heal. A small device may also be used to close the blood vessel. You may have a bandage or a compression device on each catheter site.
  • If the catheter was put in your groin, you will need to lie still and keep your leg straight for up to a few hours. The nurse may put a weighted bag on your leg to keep it still.
  • If the catheter was put in your neck or arm, you may be able to sit up right away. If it was put in your arm, you will need to keep your arm still for at least 1 hour.
  • You will be taken to an observation room where nurses and others can watch your heart rate, blood pressure, and temperature for a while and check for signs of bleeding.
  • If you have an EP study only, you may go home the same day. If you also have ablation or other treatment, you may stay overnight in the hospital.

How long the test takes

The test can take 2 to 6 hours. In rare cases, it can take longer.

How It Feels

You will feel a sharp sting when the local anesthetic is injected to numb your skin at the catheter insertion site.

You may feel pressure when the doctor moves the catheter through your blood vessel into your heart. You may feel your heart skip when the catheter touches the walls of your heart. This is normal.

The temperature in the catheterization lab is kept cool so that the equipment does not overheat. For many people, the hardest part of the test is having to lie still for an hour or longer on the table. You may feel some stiffness or cramping.

Don't be afraid to speak up if you're worried about anything during the test. The doctors, nurses, and technicians want to know exactly how you're feeling.

It's especially important to tell the doctor if you have any of these symptoms during or after the test:

  • Chest pain
  • Extreme shortness of breath
  • Dizziness
  • Trouble speaking or swallowing
  • Paralysis in any part of your body

You may have some soreness and bruising at the insertion site. It is normal for the site to feel tender for about a week.


Most people don't have problems during or after this test. You will likely have bruising and soreness where the catheters were put in.

Uncommon problems include serious bleeding after the test, puncture of the heart, and damage to the electrical system of the heart that requires a pacemaker.

Rare problems include heart attack, stroke, and death.

This test is not usually done during pregnancy, because it involves X-rays. Radiation could damage the developing fetus.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low levels used in this test. Ask your doctor about the risk of radiation for you from this test. Talk about whether you feel the benefits of the test might outweigh the risks.


An electrophysiology study will show whether you have an abnormal heartbeat that needs treatment. (Sometimes the treatment is done during the test.)


Current as of: June 24, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

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