Intracardiac electrophysiology study (EPS)

Alternative names
Electrophysiology study - intracardiac; EPS - intracardiac

Intracardiac electrophysiology study (EPS) involves placing wire electrodes within the heart to determine the characteristics of heart arrhythmias.

How the test is performed

The study is performed in a hospital laboratory by a trained staff including cardiologists, technicians, and nurses. The environment is safe and controlled to minimize any danger or risk.

The cardiologist inserts a catheter through a small incision in a vein in your arm, neck, or groin after cleansing the site and numbing it with a local anesthetic. This catheter is equipped with an electrode connected to electrocardiographic monitors

The catheter is then carefully threaded into the heart using an X-ray imaging technique called fluoroscopy to guide the insertion. Electrodes are placed in the heart to measure electrical activity along the heart’s conduction system and within heart muscle cells themselves.

Normal electrical activity is signaled from the heart’s natural pacemaker known as the sinoatrial (SA) node. It then travels through the atria (the two chambers on the top of the heart), the atrioventricular (AV) node (connecting the atria to the ventricles), and the ventricles (the lower chambers of the heart).

Abnormal electrical activity can occur anywhere along this conduction system, including in the muscle cells of either the atria or ventricles. The electrodes inserted during EPS will map the type of arrhythmia you have and where the problem arises in your heart. This information allows your cardiologist to determine the severity of the problem (including whether you are at risk for sudden cardiac death) as well as appropriate treatment.

How to prepare for the test

Test preparations are similar to those for a cardiac catheterization. Food and fluid are restricted 6 to 8 hours before the test. The procedure takes 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 regarding any changes to medications. Do not modify or stop taking any medications without consulting your health care provider.

A mild sedative is usually given 30 minutes before the procedure. You may not be able to drive home yourself if you are discharged the same day.

How the test will feel

During the test, you are awake and able to follow instructions. A small incision is made into a vein in your arm, neck, or groin in order to thread the catheter into the heart. Local anesthesia is applied to the area before the catheter is inserted. The sensation you feel is pressure (not pain) at that site.

Remaining still for a prolonged period of time may make you feel somewhat stiff and uncomfortable.

When the electrical tissue of the heart is tested, you may feel your heart beating faster or stronger. If an arrhythmia is induced as part of the test, the doctor may use medication or electrical energy to terminate it.

The procedure generally lasts from one to several hours.

Why the test is performed
Before performing EPS, which is invasive, your cardiologist will try to identify a suspected arrhythmia using other, less invasive tests like ambulatory cardiac monitoring. If the abnormal rhythm is not detected by these other methods and your symptoms suggest that you have an arrhythmia, EPS may be recommended. Additional reasons that EPS may be considered include:

  • To find the location of a known arrhythmia and determine the best therapy  
  • To assess the severity of the arrhythmia and determine if you are at risk for future cardiac events, especially sudden cardiac death  
  • To evaluate the effectiveness of medication in controlling an arrhythmia  
  • To determine if the focus (the place from where the arrhythmia is coming) should be ablated  
  • To evaluate the need for a permanent pacemaker or an implantable cardioverter-defibrillator (ICD)

If ablation is thought to be the appropriate therapy, it is performed at the time of EPS.

Normal Values

This is a very specialized procedure, and people referred for this test will almost always have arrhythmias, not normal results.

What abnormal results mean

The exact location and type of the arrhythmia may be determined so that specific therapy can be applied appropriately. The arrhythmia may originate from any area of the heart’s electrical conduction system.

For example:

  • Sick sinus syndrome occurs when the SA node of the heart malfunctions.  
  • Wolff-Parkinson-White syndrome happens if you have an extra electrical pathway leading to avoidance of the normal path through the AV node.  
  • ventricular fibrillation and ventricular tachycardia are two arrhythmias that occur if muscle cells in the ventricles inappropriately take over the electrical activity of the heart.

What the risks are

The procedure is generally very safe. Possible risks include the following:

  • Arrhythmias  
  • Cardiac arrest  
  • Trauma to the vein  
  • Low blood pressure  
  • Infection  
  • Cardiac tamponade  
  • Embolism caused by blood clots developing at the tip of the catheter

Special considerations
A catheter ablation may be performed at the same time to treat the arrhythmia.

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

Medical Encyclopedia

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0-9

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.