What is an EP Study?
An EP study is a medical procedure used to investigate arrhythmias. It allows the study of arrhythmias using fine diagnostic wires placed within the heart. These wires are threaded into in the heart via intravenous lines placed in groin region at the top of the right leg.
Who requires an EP study?
Patients are referred for EP studies for a variety of reasons.
The most common reasons include:
- To determine the cause of palpitations
- To determine the cause of blackouts or dizzy spells
- To determine the risk of developing abnormal heart rhythms
If an EP study demonstrates an arrhythmia that can be addressed during the same procedure, then catheter ablation for the problem may be performed, followed by a repeat EP study to confirm the success of the procedure.
Why do arrhythmias occur?
Arrhythmias may arise from the upper or lower chambers of the heart, and may result from either of the following reasons:
- There is an abnormal electrical channel or pathway in the heart allows an electrical short circuit to occur, taking over the heart’s normal electrical rhythm. The short circuit is usually triggered by an electrical impulse that enters the channel at a critical timing.
- There is an abnormal cluster of cells in the heart that develops the ability to fire spontaneously, overriding the heart’s normal electrical rhythm.
What types of abnormal rapid heart rhythms are there?
AV NODAL RE-ENTRY TACHYCARDIA (ANVRT)
This involves a short circuit at the AV node. Instead of a single AV node connection between the top and bottom chambers, there is a second connection that is abnormal. This extra connection has been present since birth. A single extra beat arising from anywhere in the heart may result in electrical conduction through this extra pathway. This electrical signal then gets caught up in a short circuit resulting in an abnormally fast heart rhythm.
ATRIOVENTRICULAR RE-ENTRY TACHYCARDIA (AVRT) AND WOLFF PARKINSON WHITE (WPW) SYNDROME
AVRT is an abnormal electrical circuit involving the AV node and an “accessory pathway” connecting the upper and lower chambers. An accessory pathway is a small abnormal electrical connection that has been present since birth. Most often, it occurs on the left side of the heart. A single extra beat arising from anywhere in the heart may result in electrical conduction through this extra pathway.
The electrical signal then gets caught up in a short circuit involving the pathway and the AV node, resulting in an abnormally fast heart rhythm accompanied by palpitations. The short circuit may occur in a clockwise or anticlockwise fashion. In some individuals, evidence of the accessory pathway can be seen on an ECG performed while in normal rhythm – here, the condition is called WPW syndrome.
FOCAL ATRIAL TACHYCARDIA
In patients with focal atrial tachycardia, a small cluster of cells in the heart’s upper chambers develops the abnormal ability to fire electrical impulses spontaneously, overriding the rhythm normally set by the SA node. It is not known when or why such an extra focus develops.
Atrial flutter typically refers to an electrical short circuit involving the right atrium which cycles at around 300 times per minute. The short circuit is triggered by ectopic beats or “electrical sparks” usually arising from the left atrium. During atrial flutter, both the left and right atria cannot pump effectively at this very rapid rate. The AV node will normally allow only half of these electrical impulses to reach the heart’s lower pumping chambers, resulting in a pulse rate of 150 beats per minute. Medications including beta blockers (metoprolol, atenolol, etc), calcium channel blockers (verapamil, diltiazem), and digoxin help the AV node filter out more of these rapid impulses to bring the heart rate into a normal range, even while the upper chambers remain in short circuit. Sometimes, atrial flutter circuits occur in different parts of the atria, and this is termed “atypical” atrial flutter.
VENTRICULAR TACHYCARDIA (VT)
VT arises from the lower chambers of the heart. In hearts that are otherwise structurally normal, VT usually involves a small cluster of cells that has developed the ability to fire spontaneously. In hearts that have structural abnormalities (eg, prior heart attack or heart failure), VT usually results from an abnormal electrical short circuit involving a region of scar.
How do I prepare for an EP Study?
If you are taking a medication for your heart rhythm condition, you will need to stop taking this medication 5 days prior to your procedure. You will normally be admitted on the day of your procedure. Prior to the procedure you will normally have an ECG and blood test. You will be required to fast for at least six hours before the study.
If your procedure is in the afternoon, you may have a light early breakfast. If your procedure is in the morning, Do not eat or drink after midnight, except for sips of water to help you swallow your pills.
How is an EP Study performed?
You will be transferred to the Electrophysiology Laboratory (EP lab) from your ward or from the waiting area. Usually before leaving you will be given a light sedative and your groin will be shaved. This is because 3 small tubes will need to be placed in the blood vessel at the top of the right thigh in the groin area during the EP study.
The EP lab has a patient table, X-Ray tube, ECG monitors and various equipment. The staff in the lab will all be dressed in hospital theater clothes and during the procedure will be wearing hats and masks. Many ECG monitoring electrodes will be attached to your chest area and patches to your chest and back. These patches may momentarily feel cool on your skin.
A nurse or doctor will insert an intravenous line usually into the back of your hand. This is needed as a reliable way to give you medications during the study without further injections. You will also be given further sedation if and as required. You will also have a blood-pressure cuff attached to your arm that will automatically inflate at various times throughout the procedure.
The oxygen level of your blood will also be measured during the EP study and a small plastic device will be fitted on your finger for this purpose. Your groin area and possibly your neck will be washed with an antiseptic cleansing liquid and you will be covered with sterile sheets leaving these areas exposed.
An anesthetist may be present for the procedure. The procedure is usually performed under local anaesthetic with sedative medication, and sometimes under full general anaesthetic. This will be discussed with you before the procedure. If the procedure is performed under local anaesthetic, the doctor will inject the anaesthetic to the area in the groin where the catheters are to be placed. After that, you may feel pressure as the doctor inserts the catheters but you should not feel pain. If there is any discomfort you should tell the nursing staff so that more local anaesthetic and sedative medication can be given. Occasionally it is also necessary to place a catheter in a vein in the side of the neck or just under the left collarbone.
The catheters are positioned in your heart using X-Ray guidance. Once the catheters are in place you may feel your heart being stimulated and usually your abnormal heart rhythm will be induced and studied in detail. An EP study typically takes 1 h to perform. After the type of abnormal rhythm has been identified, your doctor may proceed to treat this using catheter ablation if this has previously been discussed with you and you have provided consent. If catheter ablation is performed, this may extend the duration of the procedure by a further 1-2 hours.
What happens after an EP study?
After your procedure, you will be transferred back to your ward where you will have to lie flat for 4-6 hours. During this time, it is important to keep your legs straight and your head relaxed on the pillow. You will be discharged either on the same day or on the following day. Most patients will have 5-7 days away from work.
The groin area may feel sore and bruised for several weeks after the procedure. You should avoid strenuous physical activity and sports for 1 weeks after the procedure until this has settled. Most people take approximately 1 week off work.
If catheter ablation has been performed, some people may experience minor chest discomfort and brief palpitations due to extra beats of the heart for several days after the procedure. This is due to the irritation caused by the ablation in the heart and will settle. If this persists or is not mild, it should be reported to our team.
Some people may experience minor chest discomfort and brief palpitations due to extra beats of the heart for several days after the procedure. This is due to the irritation caused by the ablation in the heart and will settle. If this persists or is not mild, it should be reported to our team.
- Wound care. The access site at the top of the right thigh in the groin area may take several days to heal. Observe the area every day and keep it dry and clean. Avoiding applying soap and talcum powder to the site. A pea-sized lump and a minimal amount of bruising is normal and may last for up to 2 weeks. If there is increasing pain, active bleeding, or an expanding mass in the groin, please make immediate contact with the clinic, or proceed immediately to your local emergency service for assessment.
- Rest and recovery. To facilitate healing of the access site, it is best to take a week off work, particularly if your job involves physical activity. Avoid exercise, driving, abdominal straining, and heavy lifting for 5 days. Rest and gentle walking at home is permitted. After 5 days, slowly return to normal activities. After 1 week, there should be no limitations on your usual activities.
- Contact details. Prior to your first follow-up appointment, it is best to contact the treating team for any post-procedure issues rather than your GP or general cardiologist who may not be so familiar with details of the procedure. For public patients, contact the Alfred Heart Centre on 03 9076 3263. For private patients, contact the Heart Rhythm Clinic on 03 8560 0535. If the clinic is closed or the treating doctor or nurse not available, please proceed to your local emergency service for evaluation.
What risks are involved in an EP study?
This is a common and very low-risk procedure. However, should a complication arise, it will normally be dealt with immediately.
- Bleeding and bruising may occur in the right groin area; injury to adjacent nerves is very rare.
- Rapid abnormal heart rhythm – this may cause you to feel dizzy or faint and in some cases may require a small electric shock to restore normal rhythm.
- On very rare occasions there may be damage to a blood vessel or heart chamber walls.
If ablation is performed, there are small additional risks depending on the heart rhythm disorder being treated. If ablation is to be performed, this will have been discussed with you in advance, with further written information provided.
If there is a chance you are pregnant, please notify the doctor performing the procedure.