Background
A diagnostic electrophysiology (EP) study can provide important information for identifying and treating arrhythmias.  Although it is an invasive procedure, it can help diagnose the type and location of arrhythmia, evaluate the effectiveness of certain medications in controlling the arrhythmia, predict the risk of future arrhythmia events, and assess the need for an implantable device or a therapeutic procedure such as catheter ablation. 

Preparation
The patient's are instructed not to eat or drink after midnight before the procedure.  If a patient takes anti-arrhythmic medications, depending on the type of arrhythmia he/she may be asked not to take them for a few days prior to the procedure.  Also, if a patient takes coumadin (warfarin) we will ask him/her not to take it for several days prior to the procedure. 

During the procedure
The study is performed in the electrophysiology lab while the patient lies flat on an x-ray table, covered with a sterile drape. He/she will receive local anesthesia to numb the area where the physician places the catheters, usually in the groin. Since the large leg veins in this area allow catheter placement with relative ease. Typically the patient also receives intravenous sedative and pain medication. The physician inserts catheters (narrow, flexible wires) into one or more blood vessels and positions them in the heart, guided by x-ray images.  Once the catheters are positioned in the heart, electrodes at the catheter tip will measure electrical activity and can also be used to stimulate or pace the heart.  The patient may feel palpitations while the physician paces the heart in order to cause (induce) arrhythmia, to be examined. Once an arrhythmia is detected, the catheters can be used to identify the nature and the site of origin.