What is an Ablation?
Cardiac ablation is a procedure used to try to cure the symptoms from an abnormal heart rhythm either by curing the arrhythmia (by eliminating the "short circuit") or by preventing the effects of the abnormal rhythm allowing an artificial pacemaker to regulate the rhythm of the heart. It is usually performed along with an
electrophysiological study to pinpoint the abnormal pathways in the conduction system of the heart.
Catheter ablation can be used to treat a variety of abnormal heart rhythms including:
- AV Nodal Re-entrant Tachycardia (AVNRT): an extra pathway lies in or near the AV node, which causes the impulses to move in a circle and re-enter areas it already has passed through.
- Accessory Pathway: Extra pathways can exist from birth that connect the atrium and ventricles. The extra pathway causes signals to travel back to the atrium, making it beat faster. (e.g. Wolff-Parkinson-White syndrome)
- Atrial fibrillation and atrial flutter: Extra signals originating in different parts of the atrium cause the atria to beat rapidly (atrial flutter) or quiver (atrial fibrillation).
- Ventricular tachycardia: a rapid, potentially life-threatening rhythm originating from impulses in the lower chambers of the heart. The rapid rate prevents the heart from filling adequately with blood so that less blood is able to circulate through the body.
Your ablation may be performed at a hospital as a day-case (this means you arrive and leave on the same day) but usually 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. 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 procedure is performed in an X-ray room and can take anywhere from 1-4 hours.
During an ablation, a small, plastic catheter (tube) is inserted through a vein in the groin (or arm, in some cases) and is threaded into the heart, under X-ray guidance. Once in the heart, electrical signals are sent through the catheter to the heart tissue to evaluate the electrical conduction system contained within the heart muscle tissue.
The figure below shows the standard positions of catheters in the procedure as seen under fluoroscopy (X-rays) and a sample of the intracardiac electrograms at the different sites.
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.
When the area of tissue causing your tachycardia is located (the "short-circuit"), the ablation is performed 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 doctor know.
Once the procedure has been completed, the catheter(s) will be removed. The puncture in the blood vessels will be sealed 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. Your doctor will not have advised you to have an ablation 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 ablation include, but are not limited to, the following:
- stimulation of more severe rhythm problems
- permanent damage to your heart's electrical system requiring a pacemaker
- 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 ablation is considered low; but depends on the durations of the procedure. 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 ablation. Radiation exposure during pregnancy may lead to birth defects. If you are lactating, or breast-feeding, 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.