What happens during a Radiofrequency Ablation Procedure?
The EP Lab
You will be transferred to the Electrophysiology Laboratory (EP lab) from your ward. Usually before leaving your ward your groin will be shaved. The EP lab has a patient table, X-Ray tube, ECG monitors and various equipment. The staff in the lab will all be dressed in hospital theater clothes and during the procedure will be wearing hats and masks.
Many ECG monitoring electrodes will be attached to your chest area and patches to your chest and back. These patches may momentarily feel cool on your skin.
A nurse or doctor will insert an intravenous line usually into the back of your hand. This is needed as a reliable way to give you medications during the study without further injections. You will also be given further sedation if and as required. You will also have a blood-pressure cuff attached to your arm that will automatically inflate at various times throughout the procedure.
The procedure is usually performed under local anaesthetic with sedative medication rather than under a full general anaesthetic. This will be discussed with you before the procedure.
If the procedure is performed under local anaesthetic, the doctor will inject the anaesthetic to the area in the groin where the catheters are to be placed. After that, you may feel pressure as the doctor inserts the catheters but you should not feel pain. If there is any discomfort you should tell the nursing staff so that more local anaesthetic and sedative medication can be given.
How are the catheters inserted into the heart?
The catheters are inserted through intravenous ports, or sheaths, placed in the veins in the groin and sometimes through a vein on the side of the neck. To access the left ventricle, a catheter can be inserted into the heart via the aorta through an artery in the groin (similar to heart catheterization procedures). Alternatively a needle may be used to create a small puncture in the wall between the right and left sides of the heart under ultrasound guidance (called transseptal catheterization). If the left ventricle is mapped, a blood thinning medication called Heparin is given intravenously to decrease the risk of stroke during the procedure. The ablation catheter is moved around the ventricle, and a virtual 3-dimensional image of the heart is created with a computer mapping system that acts like a navigation system. The location of the catheter is determined by use of fluoroscopy (X-ray) and a 3D mapping system.
Electrical Mapping of the Heart
The catheters are positioned in your heart using X-Ray guidance. Once the catheters are in place you may feel your heart being stimulated and usually your abnormal heart rhythm will be induced. It is very important that we can induce the VT or the ventricular ectopics at the time of the procedure as we can only map the focus of the VT when it is active. The success of the procedure is determined by the ability to map the VT or ventricular ectopics on the day.
We will routinely use a three-dimensional computer mapping system to guide the ablation procedure. This will help us move the catheters in your heart without the need for X-rays and also help us create an electrical map to localize the focus of the VT. You will be given a form of intravenous adrenaline to stimulate the VT.
When the VT focus has been identified and the abnormal tissue localized, the radiofrequency ablation will be applied to this spot. This may cause a transient warm discomfort in the chest. If the focus of the VT is near aorta, a coronary angiogram will be performed prior to any ablation to ensure the coronary arteries are not damaged. Radiofrequency ablation procedures for idiopathic VT usually take approximately 2-3 hours.