Stanford Cardiac Arrhythmia Service

Electrophysiology study (EPS)

What is EPS?

We perform an Electrophysiological (or Electrophysiologic) Study (EPS) to assess serious arrhythmias because it is one of the most accurate and reliable methods of evaluating heart rhythms. The procedure is performed by an electrophysiologist, who will attempt to reproduce your arrhythmia in a controlled environment and, through careful examination, determine its type and location in your heart. Most importantly, the EPS will help your physician determine the most effective treatment of your particular arrhythmia. Based on the results, your doctor may recommend specific treatment options: catheter ablation, medication, surgery, and/or  implantable cardioverter defibrillator (ICD) or a pacemaker.

How is the study performed?

During an EPS, the doctor passes a thin, flexible wire through a vein in your upper thigh and sometimes the side of the neck to your heart. The wire records the heart’s electrical signals. Your doctor uses the wire to provide minute electrical impulses to the heart to cause the heart to beat in a specific sequence.  These extra beats may cause your heart to go into an arrhythmia. If an arrhythmia is produced, it frequently can be stopped by using another series of electrical impulses.  Sometimes, if a serious heart rhythm is produced and you begin to pass out an electrical shock to the chest will be given to convert the rhythm immediately back to normal.  Your doctor may also choose to do a catheter ablation, a procedure used to fix some types of arrhythmia, during an EPS.

Prior to your EPS, you’ll undergo a series of tests, including blood tests and an electrocardiogram (ECG). In some cases, you may be instructed not to take certain medications for several days before the EPS. Your physician will discuss specific risks of the EPS and answer any questions you may have about the procedure.

Once You Arrive

The procedure is performed in a room with specialized diagnostic equipment and heart monitoring devices. In addition to the electrophysiologist, a highly trained team of doctors, technicians, and nurses will be present. You’ll be lying flat on a table during the procedure, which can last from 2-6 hours. You’ll remain conscious during the study, but the nurse will be giving you medication to help you relax. Please tell the nurse who is monitoring you if you feel relaxed.

Initially, the nurse will apply several ECG electrodes to your chest and then cover you with sterile sheets. It’s important to keep your arms and hands under the sheets and remain on your back throughout the procedure because the area where the catheters are placed must remain sterile. After the sterile sheets are in place, the electrophysiologist will inject a local anesthetic (numbing medication) into your groin and/or neck where the electrode catheters (small plastic tubes) will be inserted. Some people will only have the catheters placed into the vein near the groin.

The anesthetic may cause a burning sensation, but it will soon numb the entire area. You should feel little discomfort while the catheters are being inserted. The electrophysiologist will use a fluoroscope, which uses small amounts of X-ray signals to allow the physician to watch the catheters as they’re guided through your veins/arteries into your heart.

During the Procedure

The catheters deliver tiny electrical impulses to cause your heart to beat in a specific pattern.  These impulses may  trigger the same type of arrhythmia that you’ve been experiencing outside the hospital. During the electrical impulses also called “pacing”, you may feel your heart skip a beat or beat quickly. The catheters also record your heart’s electrical signals, much like doing an ECG from inside the heart.  By placing the catheters in different areas of your heart, your physician can determine the location and type of the arrhythmia that you’re experiencing.  The process of determining the location of the heart rhythm problem is called “mapping”.



Copied from Biosense Webster, a Johnson & Johnson Company

The Xray images display the position of the catheters during EP study

If the arrhythmia is produced during the study, you may feel the same symptoms you’ve experienced in the past. It’s helpful to the medical team if you can describe your symptoms during the arrhythmia. It’s important that you tell the physician or nurse immediately if you feel any palpitations, dizziness, shortness of breath or chest pain. Remember, you’ll be in an extremely controlled environment and a trained medical team is standing by to relieve your symptoms immediately, if necessary.

The arrhythmia may stop by itself, but if it persists, the electrophysiologist may try to “pace” your heart out of it by delivering electrical impulses to your heart. If a very fast arrhythmia is produced, patients may need to be “shocked” out of the abnormal heartbeat with a defibrillator – a machine that delivers an electrical shock through patches placed on the chest to restore the normal rhythm. Most patients don’t feel discomfort from the “shock” because they often lose consciousness before the electrical shock is delivered as a result of inadequate pumping of blood to the brain during the fast heart rate.

In a small number of cases, if an arrhythmia can be triggered during your EPS, the electrophysiologist my want to test a medication. After the medication is given to you intravenously, the electrophysiologist will try to reproduce your arrhythmia again. If the arrhythmia cannot be reproduced, the medication is deemed likely to be effective in controlling your arrhythmia.

After the Test

The catheters will be removed after the EPS is completed and pressure will be applied to the insertion site. You’ll be returned to your room, where you need to remain flat in bed for four to six hours following the procedure so that a clot can form at the catheter insertion site.
During this time, your blood pressure, pulse and groin site will be checked frequently by the nurse. You should keep your legs straight, as bending them can loosen the clot and cause bleeding. If you experience any numbness or tingling in your arms or legs, bleeding from the catheter insertion areas, chills, fever or chest pain, notify your nurse immediately. Patients are usually allowed to eat and drink following the procedure when lying flat in bed, but please check with your nurse.
You may spend the night in the hospital if we need to observe you.

When You Go Home

If you’re able to go home after the procedure, please remember the following to ensure a quick recovery:

  1. Limit your activity the first 24 hours after you return home. You can move around, but avoid lifting or strenuous activities for 7 days but consult your physician for more information.
  2. You may shower the day after the study. If the dressing over the groin was not removed in the hospital, you can remove it the day after the procedure.
  3. At the site of insertion, you my notice a lump about the size of a walnut. This is not abnormal and can last for about three to six weeks after the swelling goes down. Warm packs may help to dissolve it more quickly. It is also normal to experience some bruising around the insertion site.
  4. If the puncture sites continue to be painful or warm to the touch, show any signs of infection or become increasingly bruised and tender, call your physician.

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