I decided to look further into this topic as we've had several of our HealingWell family that have had these EP studies done in the past, and a few that will maybe be looking into this procedure in the future. For you...
Hugs, Teri 
Electrophysiology (EP): "the branch of physiology dealing with the electric phenomena associated with the body and its functions."
"An electrophysiology (EP) study is a test done at the hospital where electrode catheters (long flexible wires) are introduced into the veins and placed under X-ray guidance into the heart." It helps to determine the characteristics of the heart arrhythmias.
http://www.heart24.com/electro.html
http://www.infoplease.com/dictionary/electrophysiology
http://www.nlm.nih.gov/medlineplus/ency/article/003867.htm