Electrophysiology (EP) study

Electrophysiology (EP) is the science of understanding, diagnosing and treating the electrical activity of the heart.

An EP study is conducted to diagnose an abnormal heart rhythm problem. This diagnostic procedure also indicates whether catheter ablation can treat the problem and if it is safe to do so. The catheter ablation procedure is usually performed directly following the EP study, while the patient is in the EP lab.

The heart's electrical systemEP Detail

  • The heart's rhythmic contractions depend on its electrical system to conduct electrical impulses throughout the heart.
  • The sinus node (SA node), a group of specialized cells in the right atrium, is where the electrical impulse normally begins. The sinus node functions as the heart's “natural pacemaker,” setting the pace for the heartbeat.
  • The electrical impulse spreads throughout the left and right atria, causing the muscle in the atrial walls to contract and squeeze blood into the ventricles.
  • From the atria, the electrical impulse reaches the atrioventricular node (AV node) located between the atria and the ventricles.
  • This node acts like a gate, slowing down each electrical impulse before allowing it to pass on to the ventricles.
  • The impulse then travels throughout the ventricles via a system of specialised muscle fibres referred to as a pathway. The impulse stimulates the ventricular muscle, causing it to contract and pump blood back into the circulatory system.


What happens during an EP study procedure?

The procedure is conducted in an angiography suite (“cath lab”) specifically set up for EP at Intra. Your electrophysiologist will be assisted by highly trained staff including an anaesthetist, anaesthetic technician, specialist nurses and a highly trained electrophysiology technician.

  • Prior to the procedure, a small intravenous needle ("IV line") will be inserted into a vein in your arm. This allows drugs to be injected directly into the vein if necessary.
  • A nurse will shave and cleanse the area where the catheters will be inserted - usually the groin area but it could be arm, shoulder or neck also. Shaving and cleansing make it easier to insert the catheters and helps avoid infection. A local anaesthetic is injected into the skin through a tiny needle to numb the area.
  • A small incision is made in the skin and a needle is used to puncture the blood vessel (usually a vein) into which the catheters will be inserted.
  • You will be given medication to help you relax during the procedure but you will remain awake. It is not uncommon to doze off. The EP  team will be monitoring your progress constantly.
  • The special electrode catheters used for the procedure 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.
  • The procedure usually is not painful although you may feel some pressure at the insertion site during the insertion of the catheters.
  • During the procedure, the cardiologist will stimulate your heart with tiny electrical impulses. You won't usually feel these, but they may induce the arrhythmia that has caused your symptoms in the past. Please let the staff know if you feel light headedness, palpitations, chest pain or shortness of breath.
  • An arrhythmia induced in the EP lab may stop by itself or be easily controlled by stimulation through the electrode catheters. If an arrhythmia persists, especially if it is very rapid, it may cause you to faint for a moment. If this occurs, the EP team may deliver an electric shock to your heart to restore a normal rhythm. (Outside the EP lab such arrhythmias could be dangerous, however, in the EP lab, well-trained personnel have the equipment and medication to handle these appropriately).

In most cases your EP study will be followed directly by catheter ablation

What does an EP Study show?

Essentially, an EP study is performed by doing two things:

1) Recording Electrical Signals
Electrode catheters sense electrical activity in various areas of the heart and measure how fast electrical impulses travel.

2) Pacing the Heart
Electrode catheters can also be used to deliver tiny electrical impulses to pace the heart. By doing so cardiologists try to induce (bring on) certain abnormal heart rhythms, so that they can be observed under controlled conditions.

In order to bring on an arrhythmia, medications may be given through an IV line to speed up the heart. The EP study helps determine the location of the heart’s abnormal electrical activity.  For example, in people with WPW several electrode catheters are inserted into the heart, to help define the exact location of the accessory pathway. This technique is called “mapping”. The location and type of rhythm problem you have will help confirm if catheter ablation is an appropriate treatment option for your condition.

Usually your EP study will be followed directly by catheter ablation.

How should I prepare for an EP procedure?

  • Fasting: You must not have anything to eat or drink 6 to 8 hours before your procedure. You may continue to drink clear fluids.
  • Medication: Be sure to check with your doctor several days before your procedure as you may be asked to stop taking certain medications for up to a week prior to the procedure. This can help get more accurate test results. Also bring a list of all the medications you are currently taking. It is important for the doctor to know the exact names and dosages of any medications that you take.
  • Allergies and previous reactions to contrast (x-ray dye): Please inform Intra staff at the time of booking your procedure if you have any known history of allergies, particularly allergies to x-ray contrast and seafood.
  • Diabetes: If you are a diabetic you should tell the Intra staff at the time of booking. You may need to discuss your insulin dose with your cardiologist.
  • Transport: Make arrangements with a family member or friend to drive you to the hospital.

On the day of your procedure, please make your way to the Mercy Hospital Reception where they will be expecting you. You will be admitted to a hospital ward and transferred to Intra for your procedure.