An electrophysiology, or EP study, is an accurate method for assessing the heart's electrical function. It allows doctors to locate abnormal sites within the heart that may be causing serious arrhythmias (abnormal heart rhythms).

During an EP study, doctors insert special electrode catheters (long, flexible wires) into veins and guide them into the heart. Once inside, the catheters can sense electrical impulses in various areas of the heart; they can also be used to stimulate different parts of the heart.

EP studies can detect life-threatening arrhythmias. They can also detect suspected arrhythmias which cannot be diagnosed using other tests.

Patients are awake during an EP study, although they are sometimes given medication to help them relax. The EP study is usually not painful, although there may be some pressure at the insertion site, and some discomfort from lying still for a long time. Patients do not feel the catheters moving through the blood vessels and into the heart.

During the procedure, doctors may induce the problematic arrhythmias under controlled laboratory conditions. Therefore, patients should let the staff know if they experience any symptoms such as lightheadedness, palpitations, chest pain or shortness of breath.

The EP study is a very safe procedure. It can also be quite lengthy, lasting from two to six hours, depending on the type of arrhythmia and the study findings.