The study is carried out in a cardiac special procedures laboratory by a trained cardiologist and technicians or nurses. Wire electrodes are placed inside the heart by catheterization techniques under fluoroscopy (rapid immediate X-ray images) and connected to electrocardiographic monitors.

The electrode is placed near the electrical conductive tissue within the heart. Impulses form the conductive tissue are then mapped and abnormalities in the conduction system can be identified. Induction of abnormal arrhythmias is often attempted with pacing (i.e., tiny electrical impulses) for any of the following reasons:

• to diagnose the source of symptoms
• to evaluate the effectiveness of medication in controlling an arrhythmia
• to evaluate the risk of future cardiac events
• to evaluate the need for a permanent pacemaker, an implantable cardioverter-defibrillator, or radiofrequency catheter ablation as a treatment for arrhythmia.

Test preparations are similar to those for a cardiac catheterization. Fast for at least 6 hours before the procedure. Specific instructions are given to you regarding medications. You must sign a consent form for the procedure. A mild sedative is usually given 1/2 hour before the procedure. You will wear hospital clothing.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

You are given sedation to relax prior to the procedure, but you are awake and able to follow instructions during the test. You will remain on a stretcher for the duration of the test. An insertion is made into a vein for threading the electrode into the heart. You are given local anesthesia, and the only sensation is one of pressure at the site. After the electrodes are in position in the heart, testing will proceed.

Discomfort may arise from having to lie still for prolonged periods of time. The procedure may last from 1 to several hours.

This is a very specialized procedure, and people referred for this test will almost always have arrhythmias, not normal results.

The exact location of the arrhythmia may be determined so that specific therapy can be instituted. The arrhythmia may originate from any area of the electrical conduction system.

Additional conditions under which the test may be performed:

• sick sinus syndrome
• Wolff-Parkinson-White syndrome

Risks of the procedure are cardiac arrhythmias, cardiac arrest, trauma to the vein, low blood pressure, infection, cardiac tamponade, and embolism from blood clots at the tip of the catheter.

This is a very specialized test offered only in certain locations.