An electrophysiology study (EP study) is a procedure in which a thin tube (catheter) is inserted into a vein or artery (e.g., in the groin) and guided to the heart, where it can perform highly specific measurements of the heart’s electrical activity and pathways. These measurements are particularly helpful in the diagnosis of abnormally fast heart rhythms (tachycardias) or abnormally slow heart rhythms (bradycardias). An EP study is typically performed only after other noninvasive tests, such as an electrocardiogram (EKG), have been performed.

The results of an EP study may lead to further treatment, such as the implantation of a pacemaker or implantable cardioverter defibrillator, or the prescription of antiarrhythmic medications. Because EP studies can pinpoint the source of abnormal electrical conduction rhythms, the physician may decide to perform a catheter ablation. This procedure destroys selected, abnormal areas of the heart’s conduction system, restoring the heart’s normal electrical activity. It is often performed in conjunction with the EP study.

If the physician does not need to do additional procedures (e.g., an ablation) during an EP study, then the patient can go home after about six hours. However, a hospital stay of up to 24 hours is usually necessary if additional treatments are performed during the EP study.

An electrophysiology study (EP study) is a procedure in which a thin tube (catheter) is inserted into a vein or artery (e.g., in the groin) and guided to the heart. The catheter is tipped with an electrode that is connected to an electrocardiograph (EKG) machine. Once inside the heart, it can perform highly specific measurements of the heart’s electrical activity and pathways. Specifically, the catheter is fed into the upper chambers of the heart (the atria), the lower chambers of the heart (the ventricles) or guided to the site of the heart’s natural pacemaker (the sinoatrial node). 

Once in place, the electrode is used to take a series of detailed measurements, tracing the progress of the electrical current through various portions of the heart's electrical conduction system. During a healthy heartbeat, an electrical signal arises from the sinoatrial node, which lies in the upper part of the right atrium. From there, the electrical signal travels through the atria, causing them to contract. The signal is next gathered at the atrioventricular node, which lies in the junction of the atria and ventricles, or upper and lower portions of the heart. From there, the signal travels through the ventricles along prescribed pathways, causing them to contract and pump blood into the arteries. The EP study is capable of measuring electrical activity very specifically in each of these areas, thus allowing physicians to exactly diagnose any abnormalities in the movement of electricity through the heart that might result in (arrhythmias).

During an EP study, the physician will also stimulate the heart to beat according to prescribed testing protocols. This may include inducing premature heartbeats, as well as specific kinds of arrhythmias. By doing this, the physician will be able to measure how well the heart's conduction system is functioning and possibly pinpoint the exact problem area. In some cases, treatment follows immediately after the irregular heartbeat is located using an ablation catheter. This instrument allows physicians to destroy the abnormal areas that are causing the arrhythmia.

EP studies can be used to diagnose the cause of abnormally slow heart rhythms (bradycardias) or abnormally fast heart rhythms (tachycardias). They are usually performed before patients undergo surgery to receive a pacemaker or implantable cardioverter defibrillator.

A newer type of catheter may help make the EP study more accurate in diagnosing paroxysmal (intermittent) atrial fibrillation. It is called the supreme spiral SC catheter. Its spiral-shaped tip allows physicians to more accurately map abnormal areas of the left atrium (the upper left chamber of the heart).

In addition, a new navigation system is being tested to increase the effectiveness of EP studies. The physician-directed, computer-controlled magnetic navigation system may assist in guiding a catheter into the heart.

Electrophysiology (EP) studies are used to locate and diagnose the cause of known arrhythmias, whether they occur in the upper chambers of the heart (atria) or lower chambers of the heart (ventricles). In general, EP studies are only recommended for patients whose conditions could not be adequately diagnosed with a standard electrocardiogram (ECG). Because the EP study is invasive, it is not considered a first-line diagnostic test for arrhythmias.

EP studies can diagnose bradycardia–related conditions such as:

EP studies can also diagnose tachycardia-related conditions, such as:

• Complex tachycardias. An EP study is used to assess those patients with possible narrow or wide QRS complexes (the electrical waves used to measure heart rhythm) whose diagnosis remains unconfirmed after an EKG, who require an assessment of treatment alternatives or in whom drug therapy is unsuccessful.
  
  
• Wolff-Parkinson-White syndrome. The EP study may be performed prior to the elimination (ablation) of abnormal electrical conduction in the heart or to gauge the effectiveness of treatments already given.
  
  
• Syncope. The EP study can help the physician to diagnose patients whose syncope (fainting) remains unexplained after tilt-table testing and other medical tests.

Furthermore, an EP study may be performed before implantation of a pacemaker. Information from the EP study is used to assist in programming the pacemaker, or after implantation in special situations where performance data cannot be retrieved from the pacemaker itself.

The EP study is also used before implantation of an implantable cardioverter defibrillator (ICD), which is often used to treat abnormally fast heart rhythms. Information from the EP study can assist the physician in selecting the appropriate type of ICD, monitoring progress during the implantation surgery, programming the device and, after the procedure, measuring device effectiveness. EP studies can also assess the effectiveness of antiarrhythmic medications.

The EP study can also determine which patient with syncope or heart dysfunction would likely benefit from placing an ICD for prevention of sudden cardiac death. Patients are considered at higher risk of fatal arrhythmias if arrhythmias (ventricular tachycardia) can be induced by electrical stimulation during EP testing.

Before the day of the electrophysiology (EP) study, patients should discuss their medical history with their physician and inform him or her of any medications currently being taken. Certain medications may need to be discontinued or dosages reduced at some point prior to the test. Also, patients with diabetes are advised to consult with their physician regarding food and insulin intake, because people are generally asked to stop eating and drinking for about six hours before the test.

Just prior to the procedure, the area to receive the electrode catheter is shaved and sterilized to prevent infection. A mild sedative is usually administered.

The EP study may take up to three hours. The patient is first taken to a sterile EP laboratory that resembles an operating room with monitoring devices, video display equipment and x-ray cameras. Once the patient is made comfortable, heart and blood pressure monitoring begin, and an intravenous (I.V.) line is inserted. The area to receive the electrode catheter is then locally anesthetized. The injection of the local anesthesia may result in a brief period of discomfort. This is normal and should be no cause for concern. In fact, this will likely be the most uncomfortable phase of the procedure.

Once the local anesthesia takes effect, the physician will prepare to insert the electrode catheter. Depending on the point of puncture (e.g., the groin), a small incision may be made or a needle may be inserted into a blood vessel. The electrode catheter, which is connected to a computer that will record the data, is then guided with the assistance of an x-ray camera toward and into the heart.

Once in place, the electrode catheter will record electrical activity to assess the presence of abnormal heart rhythms (arrhythmias). The physician may also administer a small electrical shock during the procedure in an attempt to stimulate an arrhythmia.

Depending on what the physician finds, he or she may use the opportunity to perform an ablation while the catheter is still in place. During this procedure, radiofrequency energy is used to destroy selected sections of cardiac tissue that are causing abnormal heart rhythms.

At the conclusion of all procedures, the catheter is withdrawn. Pressure is placed on the point of puncture and, if an incision was made, it will be stitched up (sutured).

After leaving the EP laboratory, patients will remain in bed with their legs straight for several hours. Medical staff will regularly check vital signs, check the point of puncture for swelling or infection, and administer pain medications as necessary. Patients may remain in the hospital for 24 hours for observation. The results of the study may be available before patients leave the hospital, or in the next few days.

Further treatment may include the implantation of a pacemaker or implantable cardioverter defibrillator or a prescription for antiarrhythmic medications.

The actual movement of the catheter should be painless, and the risk of complications during this procedure is low. Although rare, these risks include:

The risk of complications of any kind is generally less than 1 percent, but can vary depending on the number of additional procedures (e.g., catheter ablation) that may be performed during the electrophysiology (EP) study. In addition, patients with heart-related conditions such as aortic stenosis, hypertrophic obstructive cardiomyopathy and severe coronary artery disease are not considered candidates for EP testing.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to the electrophysiology study:

1. Are there any other tests I should take prior to the electrophysiology study? Will I need to take any other tests later?
   
   
2. Will I feel any pain or discomfort during the test?
   
   
3. Where will the test be conducted?
   
   
4. Do I need to make any special preparations for the test? Can I continue to take all of my regular medications?
   
   
5. What sort of test results do you expect?
   
   
6. What types of treatment could follow the electrophysiology study?
   
   
7. Could the results of the study lead to the implantation of a device such as a pacemaker or implantable cardioverter defibrillator?
   
   
8. How long will it take me to recover from the procedure?
   
   
9. Is it safe to take the electrophysiology study if I am pregnant?
   
   
10. What if the test is inconclusive? What is the next step in the diagnosis of my heart rhythm-related problems?