Cardiac electrophysiology is the study of the electrical system of the heart. 

What is an Electrophysiologist?

An electrophysiologist is a physician who specializes in the care and treatment of patients with arrhythmias. An electrophysiologist goes through additional training after internal medicine and cardiology training and therefore may be board certified in all three disciplines.

What is an EP Study?

An electrophysiology study (also known as an EP test) is a special study of your heart’s conduction system. This test helps to determine if there is an abnormality in your heart’s electrical system, which could cause your heart to beat very rapidly. In some patients who have experienced heart attacks, this test may help to assess whether or not an implantable defibrillator may be needed to prevent death from cardiac arrest.

During an EP study, special wires, called catheters, are placed into your veins (usually from the groin) and threaded into the heart. The wires are placed into your veins through special intravenous lines known as sheaths. You are given some local anesthetic so that this part of the procedure is more comfortable. In addition, you are given medications through your vein to make you sleepy. In fact, many patients sleep through their EP test. It is important to let your electrophysiologist know if you have had any reactions or allergies to medications used for sedation or anesthesia.

The EP study allows your physician to:

  • Diagnose the source of arrhythmias
  • Evaluate the effectiveness of specific medications in controlling the arrhythmia
  • Assess the need for an implantable device (a pacemaker or defibrillator) or the need for surgical correction of the arrhythmia
  • Predict the risk of sudden cardiac death

What to expect...

You will be asked to fast from midnight until after the EP test.

When you arrive, you will be admitted to a hospital room. You will also return to this room after your test.

When it is time to go for your test, you will be taken on a stretcher to the EP lab.  Nurses and technicians will position you on an x-ray table. The area where the catheters will be placed (usually the right groin) will be thoroughly cleaned and shaved if necessary. You will be covered with sterile sheets.

You will be given some medications to help you relax and sleep.

Your doctor will also inject a local anesthetic to numb the areas where the catheters will be inserted.

Once the catheters are positioned in the heart, the electrophysiologist will spend the rest of the time recording your heart’s electrical activity and making measurements.

Because part of the test involves pacing your heart and causing extra beats, you may feel your heart skipping beats and racing at times. This is not painful. If a rapid heart rhythm is started, the electrophysiologist can stop it either by using the catheters in your heart or by delivering an electric shock to your chest. In most cases, you won’t feel this because of the sedatives given during the test.

After the test is completed, the catheters and intravenous sheaths are removed.  It is necessary to hold some pressure on the insertion sites to stop the bleeding at these sites. You will be instructed not to move your leg for about 4 hours to let the area heal. This prevents bleeding.


An EP study is an invasive heart test, and does carry some risk. In general, the risks are low compared to the benefits derived from performing the test. Your electrophysiologist will discuss the risks with you in detail. One of the most common risks is mild bleeding or bruising where the catheters were inserted. To prevent this, we ask that you try not to move your legs for four hours after the study. There is a chance of serious complications, including damage to the heart, lungs or blood vessels, formation of blood clots, and infections. A heart attack, stroke or death is an extremely rare complication of an EP study (less than 1 in 1000).


Ablation is a special technique designed to cure certain arrhythmias. During an EP test, it is possible to find areas of the heart that are causing rapid or irregular heart rhythms. Some arrhythmias are caused by extra groups of cells that can cause “short circuits” in the heart. During an EP test, these areas can be mapped out. During ablation, a special catheter is placed into the heart which is used to burn away this region. If successful, ablation can cure certain arrhythmias. Ablations are most successful in patients with supraventricular tachycardia (SVT), Wolff-Parkinson-White Syndrome (WPW), and atrial flutter. However, ablations may also be used to help patients with other, more complex arrhythmias, such as ventricular tachycardia and atrial fibrillation. An ablation may be performed at the time of your EP study, or at another time. In general, ablation has a 90% success rate. This means that most ablations result in a cure of the arrhythmia. However, even if initially successful, some arrhythmias may return. The recurrence rate is from 5% to 10%, and tends to happen within the first several months. Most recurrences can be successfully treated with another ablation.


Ablation is similar to an EP study, and carries similar risks. However, since part of an ablation involves cauterizing (burning) cells inside the heart, there is an added risk to an ablation. There is a small chance that the ablation catheter will destroy some of the normal tissue inside the heart. If part of the normal conducting system is destroyed accidentally, you will need a permanent pacemaker. This is a rare complication and happens in less than 1% of cases.


A pacemaker may be inserted in patients with bradycardia (a slow heart rate) causing symptoms. A pacemaker is a device that is surgically implanted under the skin, usually near your collar bone. One or two wires are inserted through the veins and placed into the heart. A pacemaker monitors the heartbeat and sends out an electrical signal to cause the heart to beat when needed. A pacemaker keeps the heart from beating too slowly.

Implantable Cardioverter/Defibrillator (ICD)

An ICD is also surgically implanted under the skin near the clavicle. Like a pacemaker, one or two wires are implanted in the heart. The ICD has a backup pacemaker built in, but its primary function is to prevent sudden cardiac death. It does this by monitoring every heartbeat. If it notices a dangerous heart rhythm such as ventricular fibrillation, it delivers a high voltage electrical shock to restore the normal rhythm and to "restart" the heart.


Pacemaker and ICD implantations are surgical procedures and therefore carry some risk. In general, the risks are low compared to the benefits derived from performing the surgery. Your doctor will discuss the risks with you in detail prior to surgery. The most common risk is bleeding or bruising where the device is inserted. There is a chance of more serious complications, including damage to the heart, lungs or blood vessels, formation of blood clots, and infections. These generally occur less than 1 in 100 cases (less than 1%). A heart attack, stroke or death is an extremely rare complication of a pacemaker or ICD insertion, occuring in less than 1 in 1000 cases.