An Electrophysiology Study (EPS) is a minimally invasive procedure used to evaluate the heart's electrical system and identify the cause of abnormal heart rhythms (arrhythmias). During an EPS, thin, flexible wires (catheters) are guided into the heart through blood vessels, usually in the groin. These catheters record electrical signals and can be used to stimulate the heart to trigger and analyze arrhythmias, helping your doctor determine the best course of treatment.