Intracardiac electrophysiology study (EPS) is an invasive test that allows doctors to determine the details of abnormal heartbeats, or arrhythmias.

See also: Cardiac ablation procedures

The study involves placing wire electrodes in the heart to measure electrical activity along the heart's conduction system and in heart muscle cells themselves.

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

A health care provider will clean your groin area and apply a numbing medication (anesthetic). The cardiologist will then place several IVs into the groin area. Once these IVs are in place, tubes (catheters) 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 map out any abnormal heartbeats. This helps the doctor see the type of arrhythmia you have and where the problem starts in your heart.

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

Test preparations are similar to those for a cardiac catheterization. Food and fluid will be restricted 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 regarding any changes to your normal medications. Do not stop taking or change 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.

During the test, you will be awake and able to follow instructions.

A simple EPS generally lasts from 20 minutes to 1 hour. It may take longer if other procedures are involved.

Your doctor may order this test if you have signs of an abnormal heart rhythm (arrhythmia). Information from this study helps your doctor determine the severity of the arrhythmia as well as the best treatment. Before this test is done, your cardiologist may have tried other, less invasive tests such as ambulatory cardiac monitoring.

An EPS may be done to:

• Pinpoint a known arrhythmia that is beginning in the heart and help decide the best therapy
• Determine whether you are at risk for future heart events, especially sudden cardiac death
• See if medicine is controlling an abnormal heart rhythm
• Evaluate the need for a pacemaker or implantable cardioverter-defibrillator (ICD)

Abnormal results may be related to slow or fast abnormal heart rhythms. Some examples are:

• Sick sinus syndrome
• Atrial fibrillation
• Heart block
• Wolff-Parkinson-White syndrome
• Supraventricular tachycardia
• Ventricular fibrillation and ventricular tachycardia

This list may not be all-inclusive.

The health care provider must determine the exact location and type of the arrhythmia so that specific treatment can be given. The arrhythmia may start from any area of the heart's electrical conduction system.

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

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

Miller JM. Diagnosis of Cardiac Arrhythmias. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 8th ed. St. Louis, Mo: WB Saunders; 2007: chap. 32.