Intracardiac electrophysiology study (EPS)

Intracardiac electrophysiology study (EPS) is a test to look at the heart's electrical function. It allows doctors to check for abnormal heartbeats or heart rhythms.

See also: Cardiac ablation procedures

How the Test is Performed

The study involves placing wire electrodes in the heart. These electrodes measure electrical activity in the heart and its muscle cells.

The procedure is done in a hospital laboratory by trained staff that includes a cardiologist, technicians, and nurses. The environment is safe and controlled to reduce any danger or risk to the patient.

A health care provider will clean your groin area and apply a numbing medicine (anesthetic). The cardiologist will then place several IVs into the groin area. Once these IVs are in place, wires or electrodes can be passed through the IVs into the body.

The doctor uses moving x-ray images to carefully guide the catheter up into the heart and place the electrodes into the proper areas.

The electrodes detect the heart's electrical activity and are used to check the heart's electrical system.

  • Electrical signals may be used to make the heart skip beats or produce an abnormal heart rhythm. This can help the doctor understand more about what is causing the abnormal heart rhythm or where in the heart it is starting.
  • Certain medicines may also be used for the same purpose.
Cardiac conduction systemWatch this video about:Cardiac conduction system

How to Prepare for the Test

You prepare for this test much like you would for a cardiac catheterization. You will have to avoid eating or drinking for 6 - 8 hours before the test. The procedure will take place in a hospital, and you will wear hospital clothing. You must sign a consent form for the procedure.

Your health care provider will give you instructions about any changes to your normal medications. Do not stop taking or change any medications without first talking to your health care provider.

You will usually get a mild sedative 30 minutes before the procedure. You may not be able to drive home yourself if you are released the same day.

How the Test Will Feel

During the test, you will be awake and able to follow instructions. You may feel your heart skipping beats or racing at times.

A simple EPS lasts from 20 to 30 minutes. It may take longer if other procedures are involved.

Why the Test is Performed

Normally, the heart's electrical signals move through the two chambers on the top of the heart (atria), to the atrioventricular (AV) node, and then to the lower chambers of the heart (ventricles). Abnormal electrical activity can occur anywhere along this system.

Your doctor may order this test if you have signs of an abnormal heart rhythm (arrhythmia). Information from this study helps your doctor learn how severe the arrhythmia is, and the best treatment for it. Before this test is done, your cardiologist may have tried other tests, such as:

An EPS may be done to:

  • Test the function of your heart's electrical system
  • Pinpoint a known abnormal heart rhythm (arrhythmia) that is starting in the heart, and help decide the best therapy for it
  • Determine whether you are at risk for future heart events, especially sudden cardiac death
  • See if medicine is controlling an abnormal heart rhythm
  • See whether you need a pacemaker or implantable cardioverter-defibrillator (ICD)

What Abnormal Results Mean

Abnormal results may be due to slow or fast abnormal heart rhythms, such as:

This list may not include all causes of abnormal heart rhythms.

The health care provider must find the exact location and type of arrhythmia so that you can get the right treatment. The arrhythmia may start from any area of the heart's electrical system.


The procedure is generally very safe. Possible risks include:


A catheter ablation may be done during EPS to treat the arrhythmia.

Alternative Names

Electrophysiology study - intracardiac; EPS - intracardiac


Miller JM, Zipes DP. Diagnosis of cardiac arrhythmias. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 36.

Update Date: 5/16/2012

Reviewed by: Steven Kang, MD, Division of Cardiac Pacing and Electrophysiology, East Bay Arrhythmia, Cardiovascular Consultants Medical Group, Oakland, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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