Your EPS may be performed at a hospital as a day-case (this means you arrive and leave on the same day) but often you will be expected to stay one night in hospital. You will be admitted to hospital approximately 2 hours before your procedure is due. A nurse will prepare you for the procedure. The procedure is performed in an X-ray room and can take anywhere from 20 minutes to one hour. If the abnormal electric connection is identified, an ablation may be performed and the procedure will take longer. You will be mildly sedated and lying completely flat on your back. Your blood pressure and ECG will be monitored continuously during the test.

The test is performed through the blood vessels at the top of the leg and occasionally under the collar bone near the shoulder. You will receive an injection of local anaesthetic to numb the area, so it should not be too painful. Once numb, a fine plastic tube (catheter) will be inserted into the blood vessel and through this several fine wires are passed into the blood vessel.

The wires are moved through your blood vessels into the correct position in the heart. You will be able to watch the procedure on the TV screens if you wish. Once the catheter(s) are placed properly, the electrical testing will begin by sending very small electrical impulses to certain areas within the heart. You may begin to feel lightheaded or dizzy at this stage particularly if the tachycardia is triggered. The tachycardia may be treated either by giving you medication or by stimulating the heart in a different position with the wires.

If a certain area of tissue is found to be causing your tachycardia (the "short-circuit"), your doctor may perform an ablation to eliminate the tissue. This is done with radio waves (radiofrequency ablation). The radio waves are delivered through the catheter to the tissue. If you notice any discomfort or pain, such as chest pain, neck or jaw pain, back pain, arm pain, shortness of breath, or breathing difficulty, let the physician know.

Once the procedure has been completed, the catheter(s) will be removed and the bleeding stopped by gentle pressure.

Although local anaesthetic is used, there may be some discomfort as the catheters and wires are first inserted into your blood vessel. You will not feel the catheter moving in the body, but you may be aware of an occasional 'missed' heartbeat or extra beat. You may notice your heart racing like your usual palpitations, and you may even feel as though you are about to pass out. You should tell the doctor about any funny sensations as you feel them.

Some people feel a little 'washed out' after the test for a few hours. A nurse will examine you and monitor blood pressure and pulse several times after the test. Once recovered and mobile, you will be allowed home by the nurse. The place where the catheter was inserted may be tender for a few days, and there may be a small bruise.

Serious complications are very rare, but because of the nature of the test, there is always a small danger. The chance of the EPS causing a serious complication is less than 1 in 1000. The risk is higher if an ablation is performed. Your doctor will not have advised you to have an EPS unless he felt that the benefits outweigh this very small risk. You should discuss any worries with him before the test.

Possible risks of an EP study include, but are not limited to, the following:

• stimulation of more severe rhythm problems
• bleeding from the catheter insertion site(s)
• damage to the vessel at the catheter insertion site(s)
• infection of the catheter site(s)
• perforation of the heart (rare)

The amount of radiation from fluoroscopy used during an EPS procedure is considered minimal; therefore, the risk for radiation exposure is very low.

If you are pregnant or suspect that you may be pregnant, you should notify your doctor due to risk of injury to the foetus from an EP study. Radiation exposure during pregnancy may lead to birth defects. If you are lactating, or breastfeeding, you should notify your doctor.

For some patients, having to lie still on the procedure table for the length of the procedure may cause some discomfort or pain. There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.