Electrophysiology (EP) Study

An EP study or electrophysiology study of your heart is a test that looks at your heart’s electrical activity. A healthcare provider uses this information to diagnose and treat abnormal heart rhythms. This invasive test uses catheters that go into your heart to capture its signals. In some cases, providers can fix the problem during the EP study.


What is an EP study?

An electrophysiology study (EP study) is a detailed analysis of the electrical activity in your heart. Electrophysiology (EP) is a subject within cardiology that analyzes your heart’s electrical signals to diagnose and treat abnormal heart rhythms (arrhythmias).

Your healthcare provider uses cardiac catheters (small tubes) and computers to make electrocardiogram (EKG) tracings and electrical measurements from inside your heart. Sensors a provider places inside your heart provide more information than you can get from electrodes outside your chest.

Studying your heart’s electrical activity can tell your provider if and where something is going wrong with your heartbeat signals. Normally, signals that tell your heart to beat travel the same route in an organized way every time.

When you have an abnormal heart rhythm, it’s like a bus that isn’t following its normal route. The bus may start the route at the wrong bus stop, skip a stop or not travel the full route. Or it could be going too fast or too slow. Irregular signals can be like this. Your provider wants to find out why to determine whether the rhythm is dangerous and how to treat it.

How does electrophysiology work?

An electrophysiology lab is like a place for detective work. An electrophysiologist is an expert at understanding heart rhythms. They can make sense of the data from an electrocardiogram (EKG). Each of the waves on an EKG screen says something about what various parts of your heart are doing.

Electrophysiologists spend many hours studying the various EKG waves and what they should look like. They also get to know what it means when a certain wave looks different. They pay close attention to where an abnormal rhythm starts and ends on an EKG display or printout.

They can come up with a theory about what’s wrong and then test their theory in the EP lab. Using equipment and medicines like adenosine or isoproterenol, they can make your heart beat faster or slower and examine the results.

Electrophysiologists follow a logical plan for what they want to check instead of relying on what looks like an obvious answer. The information they gather may lead them to several possible diagnoses. Testing helps them narrow down the options until they can be sure they have the right diagnosis.

What is electrophysiology used for?

Your EP study can give your healthcare provider information about your abnormal heart rhythm, such as:

  • What kind of arrhythmia you have.
  • What’s causing your abnormal heart rhythm.
  • What part of your heart is causing the issue.
  • Why you’ve been feeling dizzy or fainting.
  • Where in your heart an abnormal rhythm starts.
  • Which treatment is best for you.
  • How well your medicine is working.
  • Whether you may be at risk for sudden cardiac death.

Your provider may want to do an EP study when other tests can’t provide enough information about your abnormal heart rhythm.

You may have already tried these tests:

Depending on your condition, an electrophysiologist can use the information from an EP study to treat you with catheter ablation right away. They can do this through the catheters already in place in your heart for the study.


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Test Details

How does the test work?

During your electrophysiology test, your cardiologist may safely reproduce your abnormal heart rhythm by using a catheter or medications. They can use a catheter to help determine where the rhythm is within your heart. Then they can use this information to guide what medications to use to treat it or whether to perform an ablation.

How do I prepare for an electrophysiology study?

You can prepare for your electrophysiology test in these ways:

  • Make plans to have someone drive you to and from the hospital. You won’t be able to drive until at least 24 hours after your test.
  • Talk to your healthcare provider if you have any questions or concerns about your procedure.
  • Tell your provider if you’re allergic to latex or have trouble with anesthesia.
  • Wear comfortable clothes.
  • Remove all makeup and nail polish before you come to the hospital.
  • Leave all jewelry (including wedding rings), watches and valuables at home.
  • Wear your glasses and hearing aids if you have them.

Follow these medication and food tips when preparing for your electrophysiology study:

  1. Tell your healthcare provider what you’re taking, including prescription and nonprescription drugs. This includes herbs and supplements.
  2. Bring a one-day supply of your prescription medications to your appointment. Don’t take these medications until you talk with your provider first.
  3. Ask your provider which medications you should take or stop taking before the procedure, when you should stop taking them and when you should start taking them again.
  4. Don’t stop taking any medication without consulting your provider.
  5. If you have diabetes, check with your provider about if and how to adjust your diabetes medication(s).
  6. Eat a normal meal the evening before your procedure.
  7. Don’t eat, drink or even chew anything after midnight before your test. This includes gum, mints and even water. This helps keep you safe during the procedure.
  8. If you must take medications, only take them with small sips of water.
  9. When brushing your teeth, don’t swallow any water.

What to expect on the date of an EP study

Your study will take place in a special room called the electrophysiology lab, EP lab or catheterization lab.

After you lie in a bed, your healthcare provider will:

  1. Start an IV (intravenous) line in a vein in your arm or hand. The IV will send medications and fluids into your body during your procedure.
  2. Shave your groin, arm or neck if needed and clean it with an antiseptic solution.
  3. Cover you with sterile drapes from your neck to your feet.
  4. Place a strap across your waist and arms to keep your hands from touching the sterile area.

What to expect during the electrophysiology test

Your healthcare provider will:

  1. Numb your groin, neck or arm with a special medication.
  2. Insert several catheters (narrow tubes) into a vein in your groin, neck or arm.
  3. Use a fluoroscopy (X-ray) and ultrasound machine to guide the catheters to your heart and into each of its chambers. The catheters sense and record the electrical activity in your heart, which helps your provider evaluate your heart’s conduction system.
  4. Use a pacemaker to give your heart electrical impulses through one of the catheters to increase your heart rate. You may feel your heart beating faster or stronger.
  5. Use catheter ablation to damage abnormal electrical connections that cause irregular heartbeat signals (depending on your condition).

Tell your provider about any symptoms you feel during your electrophysiology study. If an abnormal heart rhythm happens, your provider may give you medications through your IV to test how well they regulate it. If you need it, your provider can send a small amount of energy through the patches on your chest to bring your heart back into a normal rhythm.

Your healthcare team will use several kinds of equipment throughout your procedure. These include:

  • Fluoroscopy: A large X-ray machine above you helps your healthcare provider see the catheters on an X-ray screen at all times (like a video) during your procedure.
  • Defibrillator/pacemaker/cardioverter: This connects to one sticky patch on your back and one on your chest. This allows your provider to use electrical pulses to speed up a slow heart rate or disrupt an unsafe rhythm.
  • Electrocardiogram (EKG): This connects to several sticky electrode patches on your chest, as well as inside your heart. It provides a picture of the electrical impulses traveling through your heart.
  • Intracardiac echocardiogram: This is a small ultrasound that they can use within your heart to help guide the catheters during your procedure.
  • Blood pressure monitor: This connects to a blood pressure cuff on your arm and checks your blood pressure throughout your EP test.
  • Oximeter monitor: This is on a small clip on your finger. It checks your blood’s oxygen level.

What to expect after the test

After your electrophysiology study, your healthcare provider will remove the catheters from your groin, arm or neck and apply pressure to the site to prevent bleeding. You’ll:

  • Stay in bed for one to four hours after your test and keep your leg as still and straight as you can (if the catheters were in your groin).
  • Stay in the hospital if necessary, depending on your preliminary test results.
  • Have a small sterile dressing that you can remove the next day. Most people don’t need stitches.
  • Keep the incision area clean and dry.
  • Be able to eat and take medicine after your test.
  • Get back to your normal activities the day after your test, with some limits on heavy lifting for up to a week afterward.

What are the risks of this test?

An electrophysiology test is generally a very safe procedure, but it has risks. These may include:

  • Infection or bleeding where your healthcare provider put in the catheter.
  • An abnormal heart rhythm.
  • A blood clot that starts on the catheter, gets into a blood vessel and blocks it.
  • Injury to a blood vessel, heart valve or heart chamber.
  • Heart attack.
  • Stroke.

Your providers will perform the EP study in a controlled environment. They’ll take special steps to decrease your risks.

Talk to your provider about any concerns you may have about the risks and benefits of the procedure.


What are the benefits of an electrophysiology test?

An EP study can:

  • Help you get answers to your questions about what’s going on with your heart rhythm.
  • Keep you from needing to take certain medicines if a catheter ablation fixes your problem.
  • Improve your quality of life.
  • Be more cost-effective than surgery for treating an arrhythmia with a catheter ablation.

Are electrophysiology studies safe?

Yes, electrophysiology studies are safe. The risk of an EP study being fatal is 1 in 5,000.

Results and Follow-Up

What type of results do you get and what do the results mean?

Your healthcare provider will explain the type of abnormal heart rhythm you have. They’ll also decide if you need treatment for your abnormal heart rhythm, which may include:

When should I know the results of the test?

You’ll get preliminary test results right after the procedure. Based on these results, your healthcare provider will decide if you can go home or will need to stay in the hospital. They may want you to make an appointment with them to talk more about your electrophysiology study results and treatment.

If the results are abnormal, what are the next steps?

Your provider may be able to fix your issue right away with catheter ablation. If not, they’ll need to schedule other procedures or prescribe medicine for you. Even after a catheter ablation, some people need other forms of treatment, like a pacemaker.


When should I call my doctor?

Contact your healthcare provider if you have:

  • Redness, swelling or drainage at the incision site.
  • Numbness or tingling in your arm or leg that had the incision.
  • A cold feeling, loss of feeling or color change in your hand or foot on the limb that had the catheter.
  • Vomiting.
  • Chest pain.

Call 911 or your local emergency number if you have:

  • Bleeding that continues after you put pressure on your incision.
  • Swelling that gets worse without warning around your wound.

Additional Common Questions

Are you awake during an EP study?

You’ll get medication through an IV line to help you relax and make you feel drowsy. But you won’t be asleep during your electrophysiology test.

How long does an electrophysiology study take?

An EP study takes one to four hours.

Is an electrophysiology study painful?

You shouldn’t feel pain during your EP study because you’ll receive medicine to keep you comfortable. But you might feel pressure where the catheters went into your skin.

When did electrophysiology start?

Researchers started recording the heart’s electrical signals from inside the body in the late 1960s. From there, they began to map problem areas and target them with ablation.

A note from Cleveland Clinic

Having an electrophysiology study may seem like a bigger deal than the other heart tests you’ve had, but your healthcare provider scheduled it for a reason. They want to find out what’s happening in your heart so they can help you. Although an EP study is invasive, it’s a safe test that’ll give your provider the information they need to fix your abnormal heart rhythm. Your healthcare team will make sure you’re comfortable during your electrophysiology test.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 11/21/2023.

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