The four chambers of the heart are connected by an intricate electrical system that controls the rate and rhythm of the heartbeat. Electrophysiology (EP) testing uses catheters (long, thin tubes) and electrodes to diagnose problems in the heart's electrical system and to develop a course of therapy for these problems.

EP tests are used to diagnose arrhythmias, or disturbances in the rate or rhythm of the heart. Radiofrequency catheter ablation is sometimes performed as part of the EP test to destroy small amounts of heart tissue that is interfering with electrical impulses.

PRE-TEST GUIDELINES

People scheduled for an EP test should not eat or drink anything for 8 to 12 hours before the test. Because of the unpredictable length of the test, it is often recommended that the patient use the bathroom immediately before it begins.

People taking antiarrhythmic medications may be advised to stop taking them prior to an EP test, but other medications often may still be taken.

WHAT TO EXPECT

The site where the catheters will be inserted is cleaned, shaved, and numbed with a local anesthetic. Other than a sedative, patients having an EP study do not receive any anesthetics because they can alter how the heart functions.

EP tests are typically performed with the patient lying flat on a table with an x ray machine above or on the side of the table. During the EP test, electrocardiogram electrodes are placed on the patient's chest and a blood pressure cuff is placed on the patient's arm.

To perform the test, the physician threads catheters into and through the blood vessels and to the heart. Electrodes on the tip of each catheter pick up electrical activity from the heart tissue and send information to a computer. The electrodes on the tip of the catheter can also be used to send electrical signals to the heart, called pacing, so that the physician can induce and observe an arrhythmia in the heart.

An EP test can take anywhere from 1 to 6 hours. When the test is complete, the catheters are withdrawn, pressure is applied to the insertion point to control bleeding, and the person usually is asked to remain lying down for 4 to 6 hours. Within 8 hours, most people can often resume normal activity.

POST-TEST GUIDELINES

The results of an EP study can be used to prescribe or adjust antiarrhythmic medication or may indicate the need for a pacemaker or an implantable cardiac defibrillator. Heart surgery may also follow EP testing.

For arrhythmias that do not endanger normal heart function, no further treatment may be indicated.

POSSIBLE COMPLICATIONS

Complications from EP testing are usually minimal.

Very rarely during EP tests during which physicians induce arrhythmias, some individuals experience serious rhythm abnormalities, including ventricular fibrillation. The EP laboratory is equipped with a defibrillator, which delivers an electrical shock that restores normal heart rhythm.

Other potential complications include:

• Infection at the catheter insertion point;
• Bleeding;
• Blood clots in the vein;
• Perforation of the myocardium, the muscular tissue of the heart;
• Phlebitis, an inflammation of the veins;
• Stroke caused by an embolism, or blood clot; and
• Heart attack.