Electrophysiological Studies

(EP Study, EPS, Electrophysiology Studies)

What is an electrophysiological study?

An electrophysiological study (EP study) is an invasive procedure that evaluated abnormal heart rhythm disturbances.

During an EP study, small, thin wire electrodes are inserted through a vein in the groin (or neck, in some cases). The wire electrodes are threaded into the heart, using a special type of X-ray, called fluoroscopy. Once in the heart, electrical signals are measured. Electrical signals are sent through the catheter to stimulate the heart tissue to try to initiate the abnormal heart rhythm disturbances for evaluation.

There are several ways EP studies may assist in diagnosing heart rhythm abnormalities. An abnormal rhythm may be deliberately stimulated by a doctor during the EP study so that the underlying problem can be identified. The abnormal heart rhythm may also be stimulated to evaluate the effectiveness of a drug.

During the EP study, doctors may also map the spread of electrical impulses during each beat. This may be done to locate the source of an arrhythmia or abnormal heart beat. If a location is found, an ablation (elimination of the area of heart tissue causing the abnormality) may be done.

The results of the study may also help the doctor determine further therapeutic measures, such as inserting a pacemaker or implantable defibrillator, adding or changing medications, performing additional ablation procedures, or providing other treatments.

Other related procedures that may be used to assess the heart include resting or exercise electrocardiogram (ECG), Holter monitor, cardiac catheterization, chest X-ray, computed tomography (CT scan) of the chest, echocardiography, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, radionuclide angiography, and cardiac CT scans. Please see these procedures for additional information.

Reasons for the procedure

An EP study may be performed for the following reasons:

  • To evaluate symptoms such as dizziness, fainting, weakness, palpitation, or others for a rhythm problem when other noninvasive tests have been inconclusive

  • To locate the source of a rhythm problem

  • To assess the effectiveness of medication(s) given to treat a rhythm problem

  • To treat a heart rhythm problem

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

Risks of the procedure

Possible risks of an EP study include:

  • Stimulation of severe rhythm problems

  • Bleeding from the catheter insertion site(s)

  • Damage to the vessel at the catheter insertion site(s)

  • Rarely, infection of the catheter site(s)

  • Rarely, perforation of the heart

You may want to ask your doctor about the amount of radiation used during fluoroscopy and the risks related to your particular situation. It is a good idea to keep a record of your past history of 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 a long period of time.

If you are pregnant or suspect that you may be pregnant, you should notify your health care provider due to risk of injury to the fetus from an EP study. Radiation exposure during pregnancy may lead to birth defects. If you are lactating, or breastfeeding, you should notify your health care provider.

People who are allergic to or sensitive to medications or latex should notify their doctor.

For some people, having to lie still on the procedure table for the length of the procedure may cause some discomfort or pain.

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

Before the procedure

  • Your doctor will explain the procedure to you and ask if you have any questions about the procedure.

  • 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 something 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 for a certain period of time prior to the procedure. Your doctor will tell you how long to fast, usually overnight.

  • If you are pregnant or suspect that you may be pregnant, you should tell your doctor.

  • Tell your doctor if you have any body piercing on your chest and/or abdomen.

  • Tell your doctor of all medications (prescription and over-the-counter) and herbal 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. It may be necessary for you 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.

  • If a sedative is given before the procedure, you will need someone to drive you home afterwards.

  • Based on your medical condition, your doctor may request other specific preparation.

During the procedure

An EP study may be performed 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 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 excessive hair at the area of the catheter insertion (groin area), the hair may be shaved off. This will assist in healing and reduce infection after the procedure is complete.

  5. An intravenous (IV) line will be started in your hand or arm prior to the procedure for injection of medication and to administer IV fluids, if needed.

  6. You will be placed on your back on the procedure table.

  7. You will be connected to an ECG monitor that records the electrical activity of the heart and monitors the heart during the procedure using small, adhesive electrodes. Your vital signs (heart rate, blood pressure, breathing rate, and oxygenation 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 the body into the heart.

  9. You will receive a sedative medication in your IV before the procedure to help you relax. However, you will likely remain 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 after the procedure.

  11. A local anesthetic will be injected into the skin at the insertion site. 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 inserted into the blood vessel. This is a plastic tube through which the catheter will be inserted into the blood vessel and advanced into the heart.

  13. One or more catheters will be inserted through the sheath into the blood vessel. The doctor will advance the catheter 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 assist in advancing the catheter to the heart.

  14. Once the doctor has the catheter(s) placed properly, the electrical testing will begin by sending very small electrical impulses to certain areas within the heart. If a heart rhythm abnormality is started, you may begin to 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 dysrhythmia, the doctor may perform an ablation to eliminate the abnormal tissue. This is done with heat (radio waves, radiofrequency ablation) or cooling (cryothermy, 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.

  17. Once the procedure has been completed, the catheter(s) will be removed from the insertion site. The doctor or an assistant will hold pressure on the insertion site so that the blood can begin to form a clot at the site and stop the bleeding.

  18. Once the bleeding has stopped, a bandage will be placed on the site.

  19. You will be assisted to slide from the table onto a stretcher so that you can be taken to the recovery area. If the insertion was in the groin, you will not be allowed to bend your leg for a few 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.

After the procedure

In the hospital

After the procedure, you may be taken to the recovery room for observation or returned to your hospital room. You will remain flat in bed for a few hours after the procedure. The circulation and sensation of the limb where the catheter was inserted will be monitored. A nurse will monitor your vital signs, the insertion site, and circulation/sensation in the affected leg or arm.

You should immediately inform your nurse 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 in your leg or arm.

Bedrest 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, the period of bedrest will be prolonged until the sheath is removed. After the sheath is removed, you may be given a light meal.

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 resume your usual diet after the procedure, unless your doctor decides otherwise.

After the specified period of bed rest has been completed, you may get out of bed. The nurse will assist you the first time you get up, and will 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 bedrest.

When you have completed the recovery period, you may be discharged to your home unless your doctor decides otherwise. If this procedure was performed on an outpatient basis, you must have another person drive you home.

At home

Once at home, you should monitor the insertion site for bleeding, unusual pain, swelling, and abnormal discoloration or temperature change at or near the injection site. A small bruise is normal. If you notice a constant or large amount of blood at the site that cannot be contained with a small dressing, notify your doctor.

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. Your doctor will instruct you about when you can return to work and resume normal activities.

Notify your doctor to report any of the following:

  • Fever and/or chills

  • Increased pain, redness, swelling, or bleeding or other drainage from the insertion site

  • Coolness, numbness and/or tingling, or other changes in the affected extremity

  • 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.

Online resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.

This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.

American College of Cardiology

American Heart Association

Heart Rhythm Society

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

National Library of Medicine