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 one or more flexible tubes, called catheters, into a vein, typically in the groin or neck. Then he or she 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.
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Why It Is Done
An electrophysiology study is used to:
How To Prepare
Tell your doctor if you:
- Are allergic to any medicines, including iodine, or to latex.
- Have any bleeding problems.
- Are or might be pregnant.
- Have diabetes.
- Have ever had clots in your legs, groin, or pelvis.
- Have a filter in a large vein to prevent clots from traveling to the heart.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will show. To help you understand the importance of this test, fill out the medical test information form ( What is a PDF document? ).
Tell your doctors all the medicines, vitamins, supplements, and herbal remedies you take. Some of these can increase the risk of bleeding or interact with anesthesia. Your doctor will tell you which medicines to take or stop before your procedure.
If you take blood-thinning medicine, be sure to talk to your doctor. He or she will tell you if you should stop taking this medicine before your procedure. Make sure that you understand exactly what your doctor wants you to do.
Arrange for someone to take you home after the test. You may not have to stay in the hospital overnight.
Do not eat or drink (except for a small amount of water) for a few hours before the test. If you are taking any medicines, ask your doctor if you should take them on the day of the test.
Take off any nail polish. That will make it easier for doctors and nurses to check the circulation in your fingers and toes.
Be sure to empty your bladder completely just before the test.
How It Is Done
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 attached to your legs and arms with a special paste or gel. 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 (IV) needle will be inserted into a vein in one of your arms to give you fluids or medicine during the test. You will receive a medicine to help you relax (sedative) through the IV line. You may be awake during the test. But even if you are awake, the sedative may make you so sleepy that you may not remember much afterward.
- The area where the doctor plans to insert a catheter will be shaved and cleaned. Sterile towels will be draped over your body, except for the area over the insertion site.
During the test
- A local anesthetic is injected into your skin at the insertion site. This is usually in your groin or neck. When the area is numb, a doctor called a cardiac electrophysiologist inserts the catheter through your skin and into the vein.
- The doctor slowly pushes the catheter through the vein 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.
- A nurse or other assistant will help you stay comfortable and resist the urge to move around. Be careful not to touch the sheets or reach for your groin area, because you could contaminate the sterile areas and increase the risk of infection.
- Your doctor may let you watch the video monitor so you can see the pictures of your heart.
- The test can take 2 to 6 hours. In rare cases, it can take longer.
After the test
- It's important to prevent bleeding after the catheter is pulled out. For example, if the catheter was in your groin, firm pressure will be applied there for about 10 minutes to stop the bleeding. Then a pressure dressing or compression device will be placed over the area.
- 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. They also watch the pulse, color, and temperature of the arm or leg in which the catheter was placed.
- If the catheter was put in your groin, you will need to lie still and keep your leg straight for several hours. The nurse may put a weighted bag on your leg to keep it still.
- If the catheter was put in your arm, you may be able to sit up and get out of bed right away. But you will need to keep your arm still for at least 1 hour.
- If you have an EP study only, you will likely go home the same day. If you also have ablation or other treatment, you may stay overnight in the hospital. How long you stay in the hospital depends on the type of ablation you have. You may be able to go back to work and your normal routine in 1 or 2 days.
How It Feels
You will feel a sharp sting when the local anesthetic is injected to numb your skin at the catheter insertion site.
When the catheter is inserted, you may feel a brief, sharp pain. The movement of the catheter through your blood vessel may cause a feeling of pressure, but it is not usually considered painful. 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 hard 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
- 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. But call your doctor if:
- Your leg, arm, or hand becomes pale, cold, painful, or numb.
- You have redness, swelling, or discharge from the catheter insertion site.
- You have a fever.
An electrophysiology study is considered safe. The risks of this test are small.
The more common complications are not serious. They include bleeding or bruising where the catheters were put in.
Serious complications are rare. But they include extra bleeding after the test, puncture of the heart, and damage to the electrical system of the heart that requires a pacemaker.
Very serious complications, such as heart attack or stroke, are very rare.
This test is not usually done during pregnancy, because it involves X-rays. Radiation could damage the developing fetus.
Anytime you are exposed to radiation, including the low levels of X-ray used for this test, there is a chance of damage to cells or tissue. But the risk of this damage is usually very low compared to the possible benefits of the test.
An electrophysiology study will show whether you have an abnormal heartbeat that needs treatment. (Sometimes the treatment is done during the test.)
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Extreme anxiety that causes high blood pressure and irregular heartbeats.
- Kidney or liver failure.
- Not being able to follow directions during the procedure.
- Not being able to lie flat.
- Ongoing bleeding problems or infection.
What To Think About
An electrophysiology study can be scary. You may find it helpful to talk to your doctor ahead of time about your fears. If you are awake during the test, you can ask questions and let your doctor and others know how you're feeling.
Other Works Consulted
- Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
- Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
- Miller JM, Zipes DP (2015) Diagnosis of cardiac arrhythmias. In DL Mann et al., eds., Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th ed., vol. 1, pp. 662–684. Philadelphia: Saunders.
- Tedrow UB, et al. (2011). Electrophysiology and catheter-ablative techniques. In V Fuster et al., eds., Hurst's The Heart, 13th ed., vol. 1, pp. 1058–1070. New York: McGraw-Hill.
Current as ofJuly 22, 2018
Author: Healthwise Staff
Medical Review: Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine
John M. Miller MD, FACC - Cardiology, Electrophysiology