An electrophysiology (EP) study is an invasive procedure allowing detailed testing of the electrical system of the heart. Catheters are placed via veins in the leg into the heart. The test helps to determine the causes of dizziness, fainting or loss of consciousness, palpitations and rapid or 3 slow heart beats. It can also evaluate the risk of sudden cardiac death in high risk patients with heart disease. If an abnormal heart rhythm or source of palpitations is identified, it may be permanently cured by ablation (electrical cautery or freezing) during the procedure.