Electrophysiology study (EPS) is a safe procedure indicated for the evaluation of patients with certain heart rhythm disorders, loss of consciousness and assessment of risk for future cardiac events. It is an invasive procedure in which electrode catheters are passed through a large vein in the leg and positioned within the heart. Electrical signals are recorded allowing an assessment of the heart's electrical system. These same catheters can be used to pace the heart allowing further evaluation of arrhythmias. In certain cases, arrhythmias may be induced allowing them to be studied in a controlled fashion. This will aid in determining the proper effective treatment. The EP study is a sterile procedure performed in a laboratory equipped with x-ray equipment and electronic recording equipment. In general, the patient is awake and only given light sedation. A local anesthetic is used to numb the groin area where the catheters are inserted. Positioning the catheters within the heart is painless. The risks of diagnostic EP study is extremely low, lower than that of a diagnostic heart catheterization. The information learned is used to guide further treatment as indicated. In general, what is recommended depends upon the specific results of the study.