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 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.