AV Node Ablation & Pacing
How does Atrial Fibrillation occur?
In some hearts, an abnormal heart rhythm develops when an electrical impulse either starts from a different location, other than the SA node, or follows a route (or pathway) that is not normally present. This is what happens in atrial fibrillation. Multiple electrical short circuits develop in the upper heart chambers.
Atrial Fibrillation is due to multiple short circuits in the upper chambers of your heart termed the left and right atria. These rapid short circuits have several consequences:
The short circuits drive the pumping chambers very rapidly and erratically. This produces palpitations, shortness of breath, and tiredness. In some people it can also cause dizziness and chest pain. Occasionally, these may result in blackouts or heart failure.
The short circuits result in ineffective pumping of the upper chambers. This leads to slow blood flow in both of these upper chambers (the left and right atria). This can rarely cause blood clots and possibly a stroke. The reason you are taking warfarin is to thin the blood and prevent strokes.
If you were not taking warfarin, your risk of stroke would be 5-8 fold greater than a person your age without atrial fibrillation. This risk may be even greater if you have some form of heart disease. Warfarin is to date the most effective drug available for reducing your risk of stroke by 60%-70%. It is important that your INR is maintained between 2 and 4. You will need to see your General Practitioner for regular blood tests to ensure that your warfarin is maintained within these limits.
WHAT TREATMENTS ARE AVAILABLE FOR ATRIAL FIBRILLATION?
Rate Control: To control the ventricular rate to prevent deterioration in the functioning of the bottom chambers (main pumping chambers) of your heart and maintain blood thinners (warfarin). This can involve:
- Various medications that can slow the ventricular rate down.
- An ablation procedure whereby the AV node is ablated (destroyed) and pacemaker insertion. Because of the risk that atrial fibrillation may cause blood clots in the heart, most patients with this heart rhythm disturbance will require blood-thinning medication to prevent blood clots forming. At your doctors’ discretion this may either be with aspirin or warfarin. This information sheet primarily relates to the use of this procedure for your atrial fibrillation.
Rhythm Control: Therapies aimed at trying to maintain normal rhythm. This may involve:
In some people these medicines can be very effective. In others however, the medications are ineffective and may produce side effects. If you elect to take medication, your doctor will discuss the different options and the possible side effects of these medications.
- DC Shock
When the heart is in fibrillation it can be reverted to the normal rhythm with a “shock on the chest”. You receive a short general anaesthetic and the shock reverts the rhythm to normal in the majority of cases. With this approach the possibility of fibrillation returning remains present (approximately 50% of patients will have another episode of atrial fibrillation over the next year). In addition, most patients will also require medication to try to prevent the fibrillation coming back.
- A primary ablation procedure aimed at maintaining normal rhythm (sinus rhythm)
Increasingly procedures are being developed and used for the cure of atrial fibrillation. However, these do have several associated risks and are not suitable for all patients. You should have had this option discussed. If you have not, please discuss this further with the Cardiovascular Centre.
WHAT IS AV NODE ABLATION AND HOW WILL A PACEMAKER HELP?
AV node ablation and pacemaker implantation is usually reserved for patients in whom primary ablation may be too risky or when all other treatments to control the ventricular rate have been ineffective. Occasionally this may be suggested as an urgent strategy when there is evidence of worsening heart failure.
The first step is to implant the pacemaker. By itself the pacemaker will not improve the way you feel. However, following this a special procedure called AV Node ablation (sometimes also called His bundle ablation) will be performed (usually done around 6 weeks later). This procedure is a simple procedure that effectively “knocks out” the AV node. This will prevent any of the electrical short-circuits in the atria from reaching the ventricles. The pacemaker will now have complete control of your heart rhythm. The heart rhythm will be regular and will no longer race rapidly.
WHAT ARE THE ADVANTAGES OF HAVING AN AV NODE ABLATION AND PACEMAKER INSERTED?
- Your heart will no longer race rapidly but will be appropriately controlled by the pacemaker.
- Your heart rhythm will be regular.
- You will no longer require many of your medications to control the heart rhythm (you should check with your doctor as to which ones you may stop taking).
- There is a reasonable probability that you will feel very much better.
WHAT ARE THE DISADVANTAGES OF HAVING AN AV NODE ABLATION AND PACEMAKER INSERTED?
- This procedure will control the heart rhythm but the multiple short circuits in the atria will still be present. You will simply no longer be aware of them. Thus, the procedure does not cure the condition. It only treats the symptoms.
- YOU WILL STILL NEED WARFARIN.
- You will be dependent on the pacemaker.
- The procedure cannot be reversed.
PROCEDURE: WHAT IS INVOLVED IN AV NODE ABLATION?
This is usually performed approximately 4-6 weeks after the pacemaker is implanted to ensure that the pacemaker has adequately healed and is functioning properly. Occasionally it may be performed at the same time as the pacemaker implantation. The procedure is also performed in the cardiac catheter laboratory under local anaesthetic with sedative medication to make you feel relaxed and comfortable. The lab has a patient table, X-Ray tube, ECG monitors and other equipment. The staff in the lab will all be dressed in hospital theatre 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 procedure 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 oxygen level of your blood will also be measured during the procedure and a small plastic device will be fitted on your finger for this purpose. Your groin will be washed with an antiseptic cleansing liquid and you will be covered with a sterile sheet.
The doctor will inject local anaesthetic into the groin area and this will sting momentarily. After that, you may feel pressure as the doctor inserts the catheters but you should not experience any pain. The doctor will then insert a special catheter through the vein in your groin area. As this is all internal you will not feel any discomfort. This will pass via your veins up into your heart. The doctor controls its position with the aid of x-ray. A small burn will be delivered to the AV node through the tip of the catheter which essentially destroys this electrical conducting pathway.
The entire procedure takes approximately 30 minutes. You will have to lie flat for 4 hours after the procedure. You may have some bruising and discomfort in the groin area and you should avoid strenuous physical activity for at least 1 week. You will be able to go home the day after the procedure.
WHAT ARE THE RISKS OF AV NODE ABLATION?
AV Node ablation is a very common and low risk procedure. Although most people undergoing AV node ablation do not experience any complications, you should be aware of the following risks:
- Local bleeding, blood clot or haematoma (blood collection) – this may occur at the catheter insertion site.
- Perforation or damage – very slight chance that this may occur to either a heart chamber or to the wall of one of the blood vessels.
- Pacemaker failure – this is an extremely small risk.
- Stroke – prior to both procedures, if you are taking warfarin, this will need to be stopped for several days (your doctor will advise you exactly). During the time that you are not taking warfarin, there will be a very small chance of a blood clot forming and having a stroke. In addition, there is a small chance (<1%) of needing to do the ablation through the artery. In these cases there can be a small risk of stroke.
If there is any chance you may be pregnant, please notify the Cardiovascular Centre and hospital staff before your procedure. The procedure has additional risks if you are pregnant.