Atrial Fibrillation is due to the development of electrical short circuits inside the top chambers of the heart.
There are essentially 2 strategies for the treatment of Atrial Fibrillation;
The heart is a pump responsible for maintaining the blood supply to the body. It has four chambers. The two upper chambers (the right atrium and the left atrium) are the chambers that receive blood as it returns from the body via the veins. The lower chambers (the right and left ventricles) are the chambers responsible for pumping blood out to the body via the arteries.
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 travels along the heart’s conduction system (the electrical wiring of the heart). 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 lungs and body.
Atrial Fibrillation is due to the development of electrical short circuits inside the top chambers of the heart. Usually, these short circuits begin in the top chamber on the left (left atrium). These rapid short circuits have several consequences:
Your risk of stroke if you were not taking warfarin 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.
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.
There are essentially 2 strategies for the treatment of Atrial Fibrillation;
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 blood thinners (warfarin and noval oral anticoagulants – NOACS). This can involve:
A. Various medications that can slow the ventricular rate down
B. An ablation procedure whereby the AV node is ablated (destroyed) and pacemaker insertion. Due to 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.
2. Rhythm Control: Therapies aimed at trying to maintain 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. DC Shock: When the heart is in Fibrillation it can be reverted to the normal rhythm with a ‘shock on the chest’. You receive sedation and the shock reverts the 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 a medicine to try to prevent the Fibrillation coming back.
C. Ablation: 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 this option discussed.
For many years it was considered that there could be no effective means to permanently eliminate Atrial Fibrillation and restore normal rhythm (sinus rhythm). However, in the early 90’s, surgical teams demonstrated that by ‘slicing and dicing’ the atria and then sewing it back together that they could effectively eliminate Atrial Fibrillation. However, the procedure itself was extremely invasive and resulted in significant morbidity that it could not be routinely used in patients. In the late 90’s further hope was provided with the recognition that activity from the pulmonary veins (veins at the back of the heart bringing blood back to the heart from the lungs) were the ones that initiated Atrial Fibrillation in most situations (>90% of cases). This has led to ablation strategies targeting the pulmonary veins in a bid to cure Atrial Fibrillation. There have been a variety of ablation strategies that have been proposed but effectively they have all merged into quite a similar procedure. It has also become clear that while pulmonary vein ablation alone is highly effective in a selected group of patients with short episodes of Atrial Fibrillation and normal hearts, further ablation – called substrate modifications – needs to be performed in the remainder to achieve a similar degree of success.
Radiofrequency Ablation is the most common means of ablation used around the world today. It is a low power, high frequency energy that causes a tiny region of the heart near the tip of the catheter to increase in temperature, thus ablating (or cauterising) a small area of abnormal tissue. Radiofrequency energy has been used for decades by surgeons to cut tissue or to stop bleeding. For the treatment of palpitations, a much lower power of radio-frequency energy is used.
Ablation is performed around the entire circumference of the pulmonary vein to disconnect all the electrical connections between the vein and the heart. Effectively it creates a layer of insulation that prevents any abnormal electrical impulses from the pulmonary vein interacting with the heart to initiate or maintain Atrial Fibrillation. This step is performed in all patients undergoing ablation of Atrial Fibrillation.
While the pulmonary veins are recognised to be the main source of electrical activity that initiates and maintains Atrial Fibrillation, the other veins that lead into the heart can also be involved. This is increasingly recognised as potential sites that maintain longer episodes of Atrial Fibrillation, particularly in those with other heart diseases. These veins are the coronary sinus (the main vein of the heart), the superior vena cava (vein draining blood back from the top part of the body back to the heart) and infrequently the inferior vena cava (vein draining blood back from the bottom part of the body back to the heart). These veins can be isolated in a similar manner to the pulmonary veins, effectively insulating these regions from the heart. These steps are performed if we observed extra beats from these structures or if you have longer episodes of Atrial Fibrillation or have other heart
abnormalities.
This is probably the most common form of substrate modification performed to date. Essentially ablation is performed joining anatomical structures (such as two pulmonary veins or the pulmonary vein to the mitral valve). This results in an obstruction to electrical conduction and encourages Atrial Fibrillation to terminate. There may also be other potential reasons why such ablation works. Linear ablation will be performed if you have longer episodes of Atrial Fibrillation or in those with other heart abnormalities.
Several other forms of substrate modification methods have been suggested and may be variably used during your procedure. You may have read about some of these, which include ablation of complex and fractionated atrial electrograms (CFAE ablation), ablation of dominant frequency sites (DF ablation), and ablation at sites eliciting a vagal response. There is a variable amount of information supporting each of these techniques but they are used in many patients with longer durations of Atrial Fibrillation and those with other heart abnormalities.
Once you elect to undergo an Atrial Fibrillation ablation procedure, there are several steps that need to be undertaken in order that your procedure can be performed safely.
If you are unsure of any of these details prior to your procedure, please don’t hesitate to contact The Rhythm and Cardiac Specialists.
You will usually be admitted to hospital on the day of your procedure. You will be required to fast for at least six hours before the study. Prior to the procedure you will require an ECG. Once in the Electrophysiology Laboratory (EP Lab), you will be given a light sedative and 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 theatre clothes. 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 with 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 sterile sheets leaving these areas exposed.
In general, the ablation procedure is performed under general anaesthetic. The catheters are positioned in your heart using X-Ray guidance. Once the catheters are in place, your heart will be stimulated and usually your abnormal heart rhythm will be induced. Radiofrequency ablation will be applied to the regions discussed above.
The duration of the procedure is quite variable. In general, pulmonary vein isolation takes between 1 and 3 hours while additional ablation will prolong the procedure further. In cases of permanent Atrial Fibrillation, this may be considerably longer.
After the procedure you will wake up in a hospital ward called the recovery area. When you are completely awake, you will be transferred to the normal hospital ward. You will have to lie flat for approximately 6 hours after the procedure. During this time, it is important to keep your legs straight and your head relaxed on the pillow. You will stay overnight and discharge the next morning once you have been reviewed. Your heart rhythm will be monitored during your stay postoperatively. It is common to have some mild chest discomfort after the procedure. You will also have some discomfort and bruising in the groin and neck area after the procedure. This should usually improve over several days. When you go home you will need to remain on your usual blood thinning medication. You will need to continue this until your Cardiologist tells you to stop. The majority of patients have approximately 2 weeks away from work.
In the first 3 months after the procedure, you may have episodes of arrhythmias that may arise as a result of the ablation procedure. These may not be of any long-term consequence. These are much more common in people who have longer episodes of Atrial Fibrillation before the procedure or have other heart abnormalities. It is not uncommon to continue some drugs for this duration to prevent such arrhythmias. If they should be present for >48 hours, you should contact the Rhythm and Cardiac Specialists to arrange a cardioversion. If you need to be seen in hospital within the first 3 months after the ablation procedure, it is crucial that the Rhythm and Cardiac Specialists are informed and your electrophysiologist involved in your care. If you feel unwell, experience chest pain or develop fevers, it is vital that you inform the Rhythm and Cardiac Specialists.
Currently the follow up strategy is really aimed at ensuring the heart heals well after the procedure and that you do not have any Atrial Fibrillation (whether you notice it or not). In general terms, you may require 1 or 2 holter monitors over the first year, an echocardiogram and a stress test after to monitor your rhythm. The key to the success of your ablation procedure, is that we treat the conditions that may make you prone to Atrial Fibrillation.
The success rates of ablation are variably described around the world. In general, the success rate of the procedure at present is approximately 70% having no arrhythmia and without using antiarrhythmic drugs at 12 months after the procedure. These figures are much better in patients with short episodes of Atrial Fibrillation and normal hearts where it is between 85 and 90% and slightly worse in patients with permanent Atrial Fibrillation. It should be noted that approximately 1/3 of patients will require more than 1 ablation session and this improves the success further. This is either because there is recovery of previously ablated regions or that a crucial region was not ablated during the previous session. We will not know for certain whether the procedure has been successful for several months afterwards.
Sometimes it is necessary to perform a second or more procedures in order to cure the problem. This will obviously be decided later on after further discussion with you. Ablation of paroxysmal Atrial Fibrillation has been undertaken in its current form since 2000. Data suggests that if you remain without any arrhythmia over the first 12 months, you have a very good chance of remaining in a normal sinus rhythm for the next 5 years post ablation.
To date, there have been two studies that have suggested that this procedure improves survival compared to using medications. These studies need to be interpreted with caution in that they were both single centre experiences and were not a randomised study design. Similarly, there has been no data on stroke risk reduction after the ablation procedure. The cessation of warfarin or NOACS will be discussed on an individual basis with you after the procedure. With this in mind, the decision to undertake Atrial Fibrillation ablation is primarily for symptom control.
Radiofrequency ablation for Atrial Fibrillation has been developed since 2000. Most people undergoing radiofrequency ablation do not experience any complications, you should be aware of the following possible risks (all of these will be discussed with you).
In general, it has been estimated that the risk of any complication is between 4 and 6%. While much of this is related to complications related to access into the vein (local bleeding, blood clot or haematoma (large bruise) there can be more serious complications (1-2%).
Some of these are listed below;
