What is an EP study?

An EP study is an accurate method for assessing the heart’s electrical system. It allows doctors to locate abnormal sites inside the heart that may be causing serious arrhythmias (abnormal heart rhythms).

During an EP study, doctors insert special electrode catheters (long, flexible wires) into the heart. Once inside, these catheters can sense electrical activity in different areas of the heart. They can also be used to deliver tiny impulses and stimulate (or pace) parts of the heart.

Why is the EP study important?

The EP study provides more accurate and detailed information about the heart’s electrical system than other diagnostic tests. It helps doctors diagnose your problem accurately and enables them to choose the most effective treatment for you.

EP studies are most often used in people who have experience symptoms of a heart rhythm problem, such as light-headedness, fainting spells, or a rapid heartbeat. They are also used in people who have had life-threatening arrhythmias.

Preparing for the EP Study

Unless you are already in the hospital, you will most likely be asked to arrive in the morning on the day of the procedure, or possibly the night before.

Several routine tests will be done, such as an ECG and blood tests. (Blood tests may be done a day or two before the procedure.)

The doctor will review your medical history and examine you. (You may be seen by the doctor at the office several days before the procedure.)

The doctor or nurse will discuss the procedure, its purpose, potential benefits, and possible risks. This is a good time to ask questions and, most important, to share any concerns you may have. You will then be asked to sign a consent form.

A nurse will shave and cleanse the area where the catheters will be inserted. This is usually at the groin (the fold between the thigh and abdomen), although sometimes it may be at the arm, shoulder, or neck. Shaving and cleansing make it easier to insert the catheters and help avoid infection.

An IV will be inserted into a vein in you arm. This line allows drugs to be injected directly into the vein, if needed. To help you relax, you'll be given a sedative.

Before the Procedure

- Do not drink or eat anything for 6 to 8 hours before the procedure.
- You may be asked to stop certain medications for 2 or 3 days before the procedure.
- Make arrangements for someone to drive you to and from the hospital, since you will not be permitted to drive after the procedure.
- Pack a small bag for your hospital stay.
- Bring a list of all medications you are currently taking.
- Tell the doctor or nurse if you have had any allergic reactions to drugs or if you have a history of bleeding problems.
- Due to the length of the procedure, a urinary catheter may be inserted.

During the Procedure

The EP study is performed in a specially equipped room, called an EP lab.

You will be taken to the EP lab in a wheelchair or on a movable bed, then transferred to an x-ray table. The table has a large camera above it and television screens close by. There are also heart monitors and other instruments and devices.

The EP lab team usually includes a specially trained doctor (electrophysiologist), an assistant, nurses, and technologists.

Once you are positioned on the x-ray table, you will be connected to several monitors and then covered with sterile sheets. The staff will be wearing sterile gowns, gloves, and possibly masks.

The site where the catheters will be inserted is cleansed and a local anesthetic is then injected into the skin with a tiny needle to numb the area. This may cause a stinging sensation.

A small incision is made in the skin, and a needle is used to make a small hole in the blood vessel where one or more catheters will be inserted.

The special electrode catheters used during the EP study are long and flexible wires that can conduct electrical impulses to and from the heart.

One or more catheters are inserted into the body and advanced toward the heart, while the staff follows their progress on a television screen. The catheters are then positioned inside the heart chambers.

How is the EP study done?

In general terms, the EP study is performed by doing two basic things:

- Recording Electrical Signals. Electrode catheters sense electrical activity in various areas of the heart and measure how fast electrical impulses travel.
- Pacing the Heart. Electrode catheters can also be used to deliver tiny electrical impulses to pace the heart (make it beat). By pacing the heart, doctors try to induce (bring on) certain arrhythmias so that they can be observed under controlled conditions.

Inducing arrhythmias during an EP study allows doctors to test the effect of medications on your heart rhythm. For example, if the arrhythmia can no longer be induced after you are given a medication, it is likely that taking this medication will prevent similar arrhythmias in the future.

The EP study also helps determine the location of abnormal electrical pathways. For example, in people with tachycardia caused by an accessory pathway, several electrode catheters are inserted into the heart to help pinpoint the exact location of the abnormal pathway. This is called "mapping."

What can you expect?

You'll be awake during the procedure, although you may be given medication to help you relax. Let the staff know if you feel lightheadedness, palpitations, chest pain, or shortness of breath.

The procedure usually is not painful, although you may feel some pressure when the catheters are inserted. You may also feel tired and uncomfortable from lying still for a long time.

During the procedure, doctors may stimulate your heart with tiny electrical impulses. You will not feel these impulses, but they may induce the arrhythmia that has caused your symptoms in the past.

An arrhythmia induced in the EP lab will often stop by itself. If an arrhythmia persists, especially if it is very rapid, it may cause you to faint momentarily. If this occurs, the staff may deliver an electric shock to your heart to restore a normal rhythm.

Outside the EP lab, induced arrhythmias could be dangerous. In the EP lab, however, well-trained personnel have the equipment and medications to control these arrhythmias.

Depending on the particular arrhythmia you have, a complete EP study can last from 1 to 4 hours.

Is the EP study safe?

An EP study is an "invasive" procedure that requires the insertion of catheters into the body. It therefore involves some risk. The risk is small, however, and the procedure is considered quite safe.

Some patients may develop bleeding at the insertion site. Blood collects under the skin, resulting in local swelling and/or a "bruise" in the groin or arm.

In rare cases, the procedure may lead to more serious complications, including damage to the heart and blood vessels, formation of blood clots, and infection. Deaths are very rare.

Although most patients who undergo an EP study do not experience serious problems, you should be aware of the risk. To learn about your particular risk, talk with your doctor.