Children's Hospital


Electrophysiological Studies

What is an electrophysiological study?

An electrophysiological study (EP study) is a procedure used to evaluate abnormal heartbeats.

Natural electrical impulses coordinate contractions of the different parts of the heart. This helps keep blood flowing the way it should. This movement of the heart creates the heartbeat, or heart rhythm.

During an EP study, small, thin wire electrodes are put into a vein in the groin (or neck, in some cases). The wire electrodes are threaded through the vein and into the heart, using a special type of X-ray “movie,” called fluoroscopy. Once in the heart, the heart’s electrical signals are picked up by the electrodes and measured. Electrical signals are also sent through the electrodes to stimulate the heart tissue to try to cause the abnormal heart rhythm so that it can be evaluated and its cause can be found, or to help evaluate how well a drug is working.

During the EP study, doctors may also map the spread of the heart’s electrical impulses during each beat. This may be done to help locate the source of an abnormal heart beat. If a location is found, the tissue can be destroyed.

The results of the EP study may also help the doctor decide whether more treatment is needed and which treatment would be best. You may need a pacemaker or implantable defibrillator, adding or changing medications, doing more ablation procedures, or providing other treatments.


Why might I need an electrophysiological study?

An electrophysiological study (EP study) may be done for the following reasons:

  • To evaluate symptoms such as dizziness, fainting, weakness, palpitation, or others to see if they might be caused by a rhythm problem when other tests have not been clear
  • To locate the source of a heart rhythm problem
  • To see how well medication(s) given to treat a rhythm problem are working
  • To treat a heart rhythm problem

There may be other reasons for your doctor to recommend an EP study.


What are the risks of an electrophysiological study?

Possible risks of an electrophysiological study (EP study) include:

  • Severe rhythm problems
  • Bleeding and bruising at the site where the catheter(s) is put into a vein
  • Damage to the vessel that the catheter is put into
  • Formation of blood clots at the end of the catheter(s) that break off and travel into a blood vessel
  • Rarely, infection of the catheter site(s)
  • Rarely, perforation (a hole) of the heart

You may want to ask your doctor about the amount of radiation used during fluoroscopy and the risks related to your situation. It is a good idea to keep a record of your radiation exposure, such as previous scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-rays and/or treatments over time.

For some people, having to lie still on the procedure table for the length of the study may be uncomfortable or painful.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

How do I get ready for an electrophysiological study?

  • Your doctor will explain the procedure to you and give you a chance to ask questions.
  • You will be asked to sign a consent form that gives your permission to do the test. Read the form carefully and ask questions if anything is not clear.
  • Tell your doctor if you are sensitive to or are allergic to any medications, iodine, latex, tape, or anesthetic agents (local and general).
  • You will need to fast (not eat or drink anything) for a certain period prior to the procedure. Your doctor will tell you how long to fast, usually overnight.
  • If you are pregnant or think you may be, tell your doctor.
  • Tell your doctor if you have any body piercing on your chest and/or abdomen (belly).
  • Be sure your doctor knows about all medications (prescription and over-the-counter), vitamins, herbs, and supplements that you are taking.
  • Tell your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. You may need to stop some of these medications prior to the procedure.
  • Your doctor may request a blood test prior to the procedure to determine how long it takes your blood to clot. Other blood tests may be done as well.
  • A sedative (a drug to make you relax) is often given before the procedure, so you will need someone to drive you home afterwards.
  • Based on your medical condition, your doctor may request other specific preparation.

What happens during an electrophysiological study?

An electrophysiological study (EP study) may be done on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor’s practices.

Generally, an EP study follows this process:

  1. You will be asked to remove any jewelry or other objects that may interfere with the procedure.
  2. You will be asked to remove your clothing and will be given a gown to wear.
  3. You will be asked to empty your bladder prior to the procedure.
  4. If there is a lot hair at the area of the catheter insertion (often the groin area), the hair may be shaved off. This will assist in healing and reduce the chance of infection after the procedure.
  5. An intravenous (IV) line will be started in your hand or arm prior to the procedure. This is so that medication and IV fluids can be given, if needed.
  6. You will be placed on your back on the procedure table.
  7. You will be connected to an electrocardiogram (ECG) monitor that records the electrical activity of your heart and monitors your heart during the procedure using small electrodes that stick to your skin. Your vital signs (heart rate, blood pressure, breathing rate, and oxygen level) will be monitored during the procedure.
  8. There may be several monitor screens, showing your vital signs and the images of the catheter being moved through your body into your heart.
  9. You will be given a sedative in your IV before the procedure to help you relax. However, you will likely stay awake during the procedure.
  10. Your pulses below the IV site may be checked and marked with a marker so that the circulation to the limb below the site can be checked during and after the procedure.
  11. A local anesthetic will be injected into the skin at the site where the catheter and wires are to be put into the vein. You may feel some stinging at the site for a few seconds after the local anesthetic is injected.
  12. Once the local anesthetic has taken effect, a sheath, or introducer, will be put into the blood vessel. This is a plastic tube through which the catheter(s) will be put into the blood vessel and advanced into the heart.
  13. One or more catheters will be put into the sheath and into the blood vessel. The doctor will thread the catheters through the blood vessel into the right side of the heart. Fluoroscopy (a special type of X-ray that is displayed on a TV monitor), is used to help advance the catheters to the heart. Your doctor may let you watch this process on the screen.
  14. Once the doctor has the catheter(s) in the right place, the electrical testing will begin by sending very small electrical impulses to certain areas within the heart. You may feel your heart beat stronger and faster. If a heart rhythm abnormality is started, you may feel lightheaded or dizzy. Medication may be given or a shock may be delivered to stop the arrhythmia. You may be sedated before a shock is given.
  15. If a certain area of tissue is found to be causing a rhythm problem, the doctor may do an ablation to destroy the abnormal tissue. This is done with heat (radio waves, called radiofrequency ablation) or cooling (called cryothermy or cryoablation).
  16. If you notice any discomfort or pain, such as chest pain, neck or jaw pain, back pain, arm pain, shortness of breath, or breathing difficulty, let the doctor know right away.
  17. Once the EP study is done, the catheter(s) will be removed.Pressure will be put on the insertion site so that a clot will form. Once the bleeding has stopped, a very tight bandage will be placed on the site. A small sandbag or other type of weight may be placed on top of the bandage for extra pressure on the site, especially if the groin was used.
  18. The staff will help you slide from the table onto a stretcher so that you can be taken to the recovery area. If the catheter was put in the groin, you will not be allowed to bend your leg for several hours. To help you remember to keep your leg straight, the knee of the affected leg may be covered with a sheet and the ends will be tucked under the mattress on both sides of the bed to form a type of loose restraint.
  19. An electrophysiological study (EP study) may be done on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor’s practices.


What happens after an electrophysiological study?

In the hospital

After the procedure, you may be taken to the recovery room for observation or returned to your hospital room. You will stay flat in bed for several hours after the procedure. A nurse will monitor your vital signs, the insertion site, and circulation/sensation in the affected leg or arm.

You should let your nurse know right away if you feel any chest pain or tightness, or any other pain, as well as any feelings of warmth, bleeding, or pain at the insertion site.

Bed rest may vary from 2 to 6 hours depending on your specific condition.

In some cases, the sheath or introducer may be left in the insertion site. If so, you will be on bed rest until the sheath is removed. After the sheath is removed, you may be given a light meal.

After the specified period of bed rest, you may get out of bed. The nurse will help you the first time you get up, and may check your blood pressure while you are lying in bed, sitting, and standing. You should move slowly when getting up from the bed to avoid any dizziness from the long period of bed rest.

You may be given pain medication for pain or discomfort related to the insertion site or having to lie flat and still for a prolonged period.

You may go back to your usual diet after the procedure, unless your doctor tells you otherwise.

When you have recovered, you may be discharged to your home unless your doctor decides otherwise. If this procedure was done on an outpatient basis, you must have another person drive you home.

At home

Once at home, you should check the insertion site for bleeding, unusual pain, swelling, and abnormal discoloration or temperature change. A small bruise is normal. If you notice a constant or large amount of blood at the site that can’t be contained with a small dressing and stopped by putting pressure over the area, contact your doctor right away.

It will be important to keep the insertion site clean and dry. Your doctor will give you specific bathing instructions.

You may be advised not to participate in any strenuous activities for a few days after the procedure. Your doctor will tell you when you can return to work and go back to your normal activities.

Contact your doctor if you have any of the following:

  • Fever and/or chills
  • Increased pain, redness, swelling, or bleeding or other drainage where the catheter was inserted
  • Coolness, numbness and/or tingling, or other changes in the affected leg
  • Chest pain/pressure, nausea and/or vomiting, profuse sweating, dizziness, and/or fainting

Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.


Next steps

Before you agree to the test or the procedure make sure you know:

  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure

Online Medical Reviewer: newMentor board-certified, academically affiliated clinician
Online Medical Reviewer: Whittaker, Kay, MS, APRN, FNP
Last Review Date: 1/18/2014
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