Procedures

The heart is a pump responsible for maintaining blood supply to the body. It has four chambers. The two upper chambers (the right and left atrium) and the chambers that receive blood as it returns from the body via the veins. The lower chambers (the right and left ventricle) are the chambers responsible for pumping the blood out to the body via the arteries. Like any pump, the heart has an electrical system that controls how it functions.

Normal Heart Rhythm

In order for the heart to do its work (pumping blood throughout the body), it needs an electrical impulse to generate a heartbeat. Normally this electrical impulse begins in the upper right chamber of the heart (in the right atrium) in a place called the Sino-atrial (SA node). The SA node is the natural pacemaker of the heart. It provides the electrical spark that drives the heart to beat approximately 60 to 100 times per minute. If you are exercising, doing strenuous work or you are under a lot of stress, your heart rate may be faster. When you rest or sleep your heart rate will slow down. Certain medications may also slow the heart rate. All of this is appropriate.

From the SA node, the electrical impulse is relayed along the heart’s conduction system. It spreads throughout both the right and left atria causing them to contract evenly. When the impulse spreads over the right atrium and reaches the Atrio-Ventricular (AV) node. This is a very important structure in the heart because it is the only electrical connection between the top chambers and the bottom chambers. It is therefore the only way in which an electrical impulse can reach the pumping chambers (the ventricles). The impulse spreads through the AV node and down into the lower chambers or ventricles of the heart. This causes them to contract and pump blood to the body.

Atrial fibrillation is due to the development of 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. 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:

1. 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.

2. The short circuits result in effective 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 strokes. The reason you are taking warfarin or other novel oral anticoagulants (NOACS) is to thin the blood to prevent clots and potentially a stroke. Your risk of stroke if you are not taking anticoagulants would be 5 to 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.

In the majority of people who develop atrial fibrillation, the cause is not known. Usually, the heart is otherwise, sound. In some people, atrial fibrillation can develop due to other conditions such as high blood pressure, prior heart attack or leaky heart valves. Increasingly newer risk factors for the development of atrial fibrillation are emerging.

1. 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 anticoagulation therapy. This can involve:

A. Various medications that can slow the ventricular rate down

B. An ablation procedure whereby the node is ablated (destroyed) and pacemaker insertion. Because of the risk that atrial fibrillation may cause blood clots in the heart, most patients with heart rhythm disturbance will require anticoagulation medication to prevent blood clots from forming. At your doctor’s discretion, this may either be with aspirin or warfarin or other novel oral anticoagulants (NOACS).

2. Rhythm Control: Therapies aimed at trying to maintain a normal rhythm. This may involve:

A. Medication: 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.

B. Cardioversion: direct current (DC) shock. When the heart is in fibrillation it can be reverted to the normal rhythm with a “shock on the chest”. You will receive sedation, a shock is delivered which then reverts the heart’s rhythm to normal in the majority of cases. With this approach, the possibility of the 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 medicine to try to prevent the fibrillation from coming back.

AV Node ablation and pacemaker implantation are usually reserved for patients in who 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 the 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.

Advantages:

• 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 the medications that control your 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

Disadvantages:

• The 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 to take anticoagulants
• You will be dependent on the pacemaker
• The procedure cannot be reversed

Insertion of a pacemaker is a very common procedure. This is performed most times under general anaesthesia but can be performed under sedation and local anaesthesia depending on your medical history. This will be discussed with you prior to your procedure. The procedure takes approximately 1 hour and is performed in the cardiac catheter laboratory.

Prior to your procedure, you will need to stop your anticoagulant medication for a brief period. Usually, the duration is much less than that for the insertion of a pacemaker. If these arrangements have not been discussed with you or if you are unsure, please phone the Rhythm and Cardiac Specialists for any questions you may have.

After admission, you will have an ECG, a pacemaker check and possibly a blood test. You will be required to fast for at least six hours before each of the procedures.

This is usually performed approximately 4 to 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 sedation and local anaesthesia, rarely general anaesthesia is required.

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 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 oxygen level of your blood will also be measured during the EP study and a small plastic device will be fitted on your finger for this purpose. Your groin area and possibly your neck will be washed with an antiseptic cleansing liquid and you will be covered with a sterile sheet.

The doctor will inject a 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 feel 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 an x-ray. A small burn will be delivered to the AV node through the tip of the catheter. This essentially destroys this electrical conducting pathway. The entire procedure takes approximately 30 minutes. You will have to lie flat for four 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 one week. You will be able to go home the day after the procedure.

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 – a 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 anticoagulants, this will need to be stopped 1-2 days prior to your procedure (your doctor will advise you exactly) and the nurse will call you one week before. 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.