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.

Alternative Names

Electrophysiology study - intracardiac; EPS - intracardiac

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.

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

Other procedures that may also be done during the test:

  • Placement of a heart pacemaker
  • Procedure to destroy small areas in your heart that may be causing your heart rhythm problems (called catheter ablation)

How to prepare for the test

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 instruct you about any changes you must make 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. The procedure may last from 1 hour to several hours. You may not be able to drive home yourself, even if you are released the same day.

How the test will feel

You will be awake during the test. You may feel some discomfort when the IV is placed into your arm. You may also feel some pressure at the site when the catheter is inserted. You may feel your heart skipping beats or racing at times.

Why the test is performed

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 recommended that you have other tests.

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:

  • Atrial fibrillation or flutter
  • Heart block
  • Sick sinus syndrome
  • Supraventricular tachycardia (a collection of abnormal heart rhythms that start in the upper chambers of the heart)
  • Ventricular fibrillation and ventricular tachycardia
  • Wolff-Parkinson-White syndrome

This list does 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.

What the risks are

The procedure is generally very safe. Possible risks include:

  • Arrhythmias
  • Bleeding
  • Blood clots that lead to embolism
  • Cardiac tamponade
  • Heart attack
  • Infection
  • Injury to the vein
  • Low blood pressure
  • Stroke


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.

Olgin JE. Approach to the patient with suspected arrhythmia. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 62.

Review Date: 6/18/2012

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