Your Heart’s Electrical System

Your heart has an electrical system that controls the speed and pattern of your heart beat. A normal “sinus rhythm” starts from the Sinoatrial (SA) node and spreads down to the Atrioventricular (AV) node as the atria contract and force blood into the ventricles. The ventricles then contract and pump blood out of the heart as electrical signals reach the ventricular muscle cells.

Problems with this system can make your heart beat too slowly or too quickly. They can cause symptoms such as dizziness, faint episodes or shortness of breath. If your cardiologist suspects that you have a heart rhythm problem (arrhythmia), he or she may order this EP study to learn more about your heart.

What are the symptoms of a Heart Rhythm Problem?

A heart rhythm problem affects the ability of your heart to pump blood well to the rest of your body. If the rhythm is too fast or too slow, the changes in the blood flow can cause symptoms ranging from mild to severe.

These symptoms can include:

  • Palpitations (a fluttering sensation in the chest)
  • Dizziness or lightheadness
  • Fainting or blackout spells (syncope)
  • Shortness of breath
  • Chest tightness or jaw discomfort
  • Generalized weakness
  • Reduction in exercise tolerance

What is an Electrophysiological study?

An Electrophysiological study (EP Study) is a procedure by which a detailed evaluation of the electrical activity in your heart is performed. Specialized cardiac catheters and computers are used to create electrocardiogram (EKG) tracings and electrical measurements to create an internal electrical map of your heart.

During the test, your cardiologist may also safely reproduce your abnormal heart rhythm and give you medications to see which one best controls the rhythm.

Why do I need an EP Study?

This test is very useful when other tests such as a standard electrocardiogram (ECG), Holter monitoring, stress tests or coronary angiogram cannot provide enough information to thoroughly evaluate your abnormal heart rhythm.

It helps your cardiologist understand the way electrical signals move through your heart to make it beat. It is typically used in patients whose bodies produce ineffective or chaotic electrical signals that cause the heart to beat irregularly.

Your cardiologist will use the results of your EP Study to

  • Find out what is causing your abnormal heart rhythm (also called arrhythmia or dysrhythmia)
  • Determine where in your heart the abnormal heart rhythm begins
  • Decide which treatment is best for your abnormal heart rhythm
  • Predict your risk of sudden cardiac arrest and how best to prevent it
  • Evaluate the cause of temporary loss of consciousness (syncope)

An EP tracing obtained during an electrophysiological study

How should I prepare for procedure?

Before the day of the procedure

  • Your cardiologist will explain how the procedure is performed, the risks and benefits and expected duration of stay in the hospital.
  • Informed consent will be obtained.
  • Routine blood tests and ECG will be done before the procedure.
  • Instructions for medications
  1. Blood thinners should be stopped 2 days before the procedure at the advise of your doctor. These include:
  • Warfarin (Coumadin; Marevan)
  • Dabigatran (Pradaxa)
  • Apixaban (Elequis)
  • Rivaroxaban (Xarelto)
    • Please discuss with your doctors if Aspirin and/or Clopidogrel needs to be stopped before the procedure.
    • Arrange for an adult family member or friend to give you a ride home after the procedure.

    On the day of the procedure

    • ARRIVE PUCTURALLY – Proceed to the admission office where the staff will settle you comfortably in your room.
    • FASTING - You may drink water, consume a light breakfast (eg cereal/eggs/toast/milo) 4 hours before your procedure. Please keep nil by mouth thereafter. Food will be provided for you after the procedure.
    • MEDICATIONS - Please consume all your prescribed medications with plain water on the morning of your procedure. Bring all your medications with you.
    • ATTIRE - Come in casual comfortable attire and bring your toiletries, an extra set of clothes & undergarments.
    • ALLERGIES – Please inform your doctor if you are allergic to any drugs, latex, tape, local or general anesthesia (numbing medicines or medicines used to make you sleepy).
    • A SMALL IV CANNULA will be inserted in one of the veins of your hand to facilitate administration of medications.

    Where is the procedure performed?

    • This test is usually done as a Day Surgery procedure in the Electrophysiology Lab in the X-ray department (not in the operating theatre).
    • The following equipment is what you will see in the EP Lab:
    1. X-ray Equipment – sends pictures to be viewed on monitors
    2. Video monitors – show the X-ray pictures, which are used to guide catheters to your heart
    3. ECG monitor – continuously monitors your heart rhythm

      How is the procedure performed?

    Before the procedure

    • You will be asked to empty your bladder before the procedure.
    • You will change into a hospital gown and brought to the Electrophysiology Lab where your cardiologist together with a specialized team of cardiac technologists, radiographers and nurses will be on standby to do the procedure
    • The nurse will record your height, weight and blood pressure and insert an intravenous (IV) cannula into a vein in your arm.
    • You will lie on a movable X-ray table equipped with X-ray cameras and heart monitors.
    • Three electrodes (small flat sticky patches) will be placed on your chest wall and attached to an ECG monitor that charts your heart’s electrical activity during the test.
    • A mild sedative will be given by an anesthetist and this will make you sleepy and relaxed but arousable.
    • You will be covered with a sterile drape and a nurse will shave your groin and clean it with a cool antiseptic solution.

    During the procedure

    The procedure is broken up into 2 parts. The first part is obtaining vascular access and the second part is performing the EP study.

    Obtaining vascular access

    • A local anaesthetic is injected into the skin of your groin, causing a temporary stinging sensation. Once the site is numb, a few small 2-3 mm plastic sheaths are inserted into the femoral vein in the groin.
    • This step typically takes 10-15mins.

    Performing the EP study

    Specialized catheters that can sense the electrical activity in your heart will be advanced under X-ray guidance to your heart. Several techniques that may be used during the EP study include:

    1. 1
      Taking a baseline measurement of the electrical activity in your heart.
    • A diagnostic catheter will be placed in various locations in your heart and the electrical activity will be recorded (intracardiac electrogram).
    • The results from each part of your heart give your cardiologist a better idea of how the electrical signals are moving through your heart.
    1. 2
      Using an electrode to trigger an abnormal heart rhythm.
    • Pacemakers will be used to give the heart electrical impulses through one of the catheters to increase your heart rate.
    • Your heart's reaction to the stimulus is recorded. By placing the electrode in different areas of your heart, your cardiologist can determine if you have extra electrical signals in your heart and where those signals are coming from.
    • If your abnormal heart rhythm (arrhythmia) occurs, your cardiologist may give you medications through your IV to test their effectiveness in controlling it.
    • If needed, a small amount of energy may be delivered through the patches on your chest to bring your heart back into a normal rhythm.
    1. 3
      Mapping the heart in preparation for cardiac ablation
    • Cardiac mapping is the process of determining the best location to apply cardiac ablation to treat the arrhythmia responsible for your symptoms.

    Cardiac Ablation

    If cardiac ablation is appropriate, your cardiologist will continue with that procedure during your EP study. Cardiac ablation involves using special catheters to apply heat or cold energy to areas of your heart. The energy creates scar tissue that blocks the erratic electrical signals in your heart.

    How will I feel during the procedure?

    • You may feel your heart beating faster or stronger.
    • Please tell your cardiologist about any symptoms you feel during the procedure.
    • This procedure typically takes 2 to 4 hours.

    What happens after the procedure is completed?

    • The sheath in your groin will be removed with a pressure dressing compressing the site of puncture.
    • You will be brought back to the day surgery ward to rest for a few hours.
    • You will be able to have your breakfast or lunch with your medications.
    • You will need to stay in bed and keep your leg as still as possible for one to two hours. Once the puncture site is stable with no bleeding, a small sterile dressing will be applied and it can be removed the next day.
    • Clear instructions about how to take care of the access site following the procedure will be given.

    How does the doctor use the results to treat me?

    You will receive the preliminary results of your EP study after the procedure. Based on these results, your cardiologist will determine if you are able to go home or will need to stay in the hospital. In some cases, no treatment is needed.

    In other cases, the following treatments may be needed:

    1. Medications

    • Medications to control your heart rhythm (anti-arrhythmics) may be started by your cardiologist and you must be sure to take the medications as prescribed. Keep your doctor informed about any side effects you may have.

    2. Catheter ablation


    3. Device implantation e.g. a pacemaker

    • Radio frequency waves are sent through an ablating electrode catheter placed in your heart to destroy (ablate) abnormal electrical pathways or groups of cells that may be causing the arrhythmia.
    • This is common treatment of heart rhythm problems such as atrial fibrillation, atrial flutter, and other supraventricular tachyarrhythmias

    Is this procedure safe?

    In recommending this procedure, your cardiologist has balanced the benefits and risks of the procedure against the benefits and risks of not proceeding. Your doctor believes there is a net benefit to you going ahead. The procedure is performed by cardiologists and nurses who specialize in electrophysiology.

    An EP study is generally a very safe procedure. However, as with any invasive procedure, there are risks and special precautions will be taken to decrease these risks.

    The complications from an EP study include:

    Common risks (more than 5%)

    • Minor bleeding or infection at the puncture site
    • Abnormal heartbeat lasting several seconds which settles by itself

    Uncommon risks (1-5%)

    • Unable to get the catheter into the leg vein - the procedure may be changed to the opposite leg
    • Abnormal heart rhythm that continues for a long time - this may need an electric shock to correct.
    • The femoral artery (in the groin) is accidentally punctured - this usually just requires pressure on the artery.
    • Damage to the blood vessels where the catheter travelled to get to the heart

    Rare risks (less than 1%)

    • Damage to the heart muscle or valves
    • Damage to your heart's electrical system, which could worsen your arrhythmia and require a pacemaker to correct
    • Development of blood clots in the legs or lungs
    • Collapsed lung (Pneumothroax)
    • Stroke or Heart attack (very rare)
    • Death in extremely rare cases

    Please talk to your cardiologist about any concerns you may have about the risks and benefits of the procedure.

    Don't wait for your symptoms to worsen.

    Early intervention can save your life. Heart conditions if left unchecked may lead to serious consequences that may have been avoidable with early treatment. Get peace of mind and let us help you find out if there's an underlying cause to your symptoms and provide a suitable treatment plan.

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