An electrophysiology (EP) study is a test that can precisely record the electrical activity inside the heart. It is often used to determine whether there is an extra electrical pathway inside the heart and, if so, where it is located.

During an EP test, one or more thin, flexible wires are inserted into veins in the arm, groin, or neck and threaded into the heart. Small electrical conductors (called electrodes) on the ends of these wires are positioned inside the heart to measure electrical signals. The wires transmit information about the electrical activity to a machine that measures and records the activity. The information can be displayed on a screen or printed onto a paper tracing for a more detailed picture of how electrical signals flow inside the heart.

Electrical currents can also be sent through the wires into the heart (pacing). This is done during the procedure to determine whether abnormal rhythms can be triggered in the heart. This allows the doctor to determine the type of heart rhythm abnormality and the best way to treat it.

Extra electrical pathways can sometimes be located and destroyed during an EP study. This is called catheter ablation. Catheter ablation selectively destroys areas of the heart that are causing a heart rhythm problem.

During the EP study, your doctor will find the tiny areas that are causing the rhythm problem. Then, the wires in your heart are used to send energy to those areas in the heart. This energy is in the form of heat or freezing cold. The heat or cold destroys, or ablates, the heart tissue. Destroying this tissue can cure your heart rhythm problem.

Catheter ablation can be called different names based on the type of energy used to create the heat or cold. If heat from radio waves is used, it is called radiofrequency catheter ablation. If cold temperatures are used, it is called cryoablation.

An EP study can take several hours and can be slightly uncomfortable. You may be awake during this test, but you may be given a mild sedative to help you relax. Strong sedatives are usually not used because they may change the heart's electrical activity and affect the test results.

Complications during the test are uncommon but may include:

• Bruising where the catheter is inserted.
• Bleeding.
• Formation of a blood clot.
• Infection.
• An abnormal heartbeat (arrhythmia) that cannot be controlled.
• Damage to the electrical system of the heart, requiring placement of a pacemaker.
• Puncture of the heart.