Treatments to Restore Normal Rhythm
In many instances when AF causes significant symptoms or is negatively impacting health the major goal of treatment is to restore normal rhythm and prevent recurrence of episodes of AF. Treatment options to restore normal rhythm need to be individualised and may be adjusted over time.
'Antiarrhythmic drugs' refers to a group of medications, which are designed to suppress the onset of arrhythmia and to help maintain the heart in normal rhythm. They are used to treat AF but are also used for treatment of other heart rhythm conditions. The different medications may vary in their efficacy in controlling AF from person to person and also have different possible side effects and potential safety issues.
- Amiodarone – A very effective medication for preventing and treating episodes of AF. It has some potential serious, but rare, side effects especially when used over a prolonged period of years. It is often used after other medications have been tried and have been unsuccessful. It can be used in patients with any type of underlying heart conditions.
- Flecainide – A very effective medication for preventing and treating episodes of AF. It probably has the least side effects but cannot be used in people who have had a heart attack, significant coronary artery blockages or weakness of the heart muscle.
- Sotalol - A useful medication for preventing AF episodes. It is from a class of medications called beta-blockers (which counteract the effects of adrenaline on the body and heart) but has additional rhythm stabilising properties. It may have effects on lowering blood pressure also. Rarely it can lead to a dangerous heart rhythm disturbance from interactions with other medications. You should always tell your doctors and your pharmacist if you are taking Sotalol when a new medication is being prescribed.
For people who are in continuous AF and the rhythm has not returned to normal on its own a cardioversion procedure may be required to restore the normal heart rhythm.
Electrical cardioversion (also known as direct-current or DC cardioversion) is a procedure whereby a synchronised electrical current (shock) is delivered through the chest wall to the heart. The shock is delivered through special adhesive electrodes or paddles on the chest and back. The purpose of the cardioversion is to interrupt the abnormal electrical signals in the heart and to restore a normal heartbeat, like rebooting a computer. The delivered shock causes all the heart cells to contract simultaneously, thereby interrupting and terminating the abnormal electrical rhythm without damaging the heart. The heart's electrical trigger then restarts the normal heart rhythm. The procedure is performed under anesthesia in hospital, often as a day patient. Sometimes a cardioversion procedure is combined with a transoesophageal echocardiogram procedure at the same time. There are special requirements for "blood thinner" treatment around the time of cardioversion.
A small number of people with AF may also have an abnormality of the heart's natural pacemaker or electrical trigger (called the "sinus node"), which controls the normal heart rhythm. The heart may beat too slowly or even pause at times. This condition is called "sick sinus syndrome". Drug treatments for AF may worsen the problem. Implant of a permanent pacemaker may be required to correct "slow heart beats" while drug treatments for AF are continued to correct fast or erratic heart rhythms.
What is it?
Catheter ablation is a procedure that uses special wires that are advanced into the heart to give treatment to abnormal electrical impulses that cause heart rhythm problems (arrhythmias). In people who experience AF, the treatment is directed around the pulmonary veins (blood vessels bringing blood back from the lungs to the heart) where they connect to the left atrium (left top chamber of the heart). Research has shown that most abnormal electrical impulses that trigger episodes of atrial fibrillation come from this region of the heart.
Why perform ablation for AF?
Some people continue to experience significant symptoms from their AF despite having tried several medications and other treatments such as cardioversions. Catheter ablation is a new treatment, which is effective at controlling or even curing atrial fibrillation in such people.
How successful is the procedure?
The success rates of this type of treatment for restoring and maintaining normal heart rhythm for at least 1 year are greater than 70% in people who are having intermittent episodes of AF. The success rates are lower if the heart has been in AF persistently for some time. Several techniques for catheter ablation for atrial fibrillation have been developed around the world with varying success rates according to technique and the amount of training and experience of the Cardiologist performing the procedure. Small numbers of patients can get their AF back over time, in which case medications can be retried or a repeat procedure can be performed to improve the success.
What does the procedure involve?
The procedure is performed under a general anaesthetic in a special operating theatre called the Cardiac Catheterisation Laboratory. While the patient is asleep, small incisions are made in both groins and several catheters are passed up through the veins into the heart. Two small punctures are made from inside the heart to advance the catheters across into the left atrium where the treatment will be delivered. Intracardiac echocardiography is used to visualise and aid the punctures.
First, information is collected with the catheters from the inside of the heart with the assistance of a 3D mapping system. Then ablation treatment is performed around each of the connections of the pulmonary veins with the left atrium. Information is then recollected to ensure that electrical impulses are no longer able to exit from inside of the pulmonary veins to trigger AF (so called "pulmonary vein isolation"). Other areas of the heart will be checked for abnormal electrical impulses, which could cause AF, and additional treatment may be performed.
At the completion of the procedure pressure is applied to seal over the incisions. The patient is taken to recovery and then back to a ward bed for monitoring overnight.
An important safety aspect of the procedure is preventing blood clot from forming on the catheters during the procedure, or inside the heart during the healing period, which could potentially travel off in the bloodstream and cause a stroke. Patients are required to take anticoagulation treatment for three months after the procedure, and sometimes before. Additional blood thinners are used during the ablation procedure.
During atrial fibrillation the upper chambers of the heart quiver rapidly instead of their normal pumping action, which may allow blood to stagnate, and blood clots to form inside the heart. The majority of blood clots form within a blind-ending pocket (called the left atrial appendage) attached to the left upper chamber. If a blood clot dislodges and travels to the brain a stroke may result.
Who is at highest risk?
Some people may go through their lives with AF and never have a stroke, but yet others will. Several characteristics increase a person's risk of having a stroke – these include:
- History of high blood pressure, even when treated
- Increasing age (in particular >75 years old),
- Heart failure or weakened heart pump function,
- History of a prior stroke or TIA (transient ischaemic attack),
- Vascular disease of the arteries,
- Female gender.
These characteristics are termed risk factors and make up the CHADSVASc score (see below) that is used to guide treatment decisions for stroke prevention.
In general, the more risk factors the higher the risk of stroke. The risk of having a stroke each year varies from around 1% for people with no risk factors through to about 23% for a person with all of these characteristics.
The CHADSVASC score is a stroke risk stratification tool in patients with atrial fibrillation (who do not have Rheumatic heart valve disease) and is used to determine the level of anticoagulation therapy required. The higher the score, the greater the risk of stroke.
The CHADSVASC scoring table is shown below. Adding together the points that correspond to the patient's conditions will result in a score that is used to estimate stroke risk:
|C||Congestive Heart Failure||1|
|H||Hypertension (or treated hypertension)||1|
|A2||Age > 75 years||2|
|S2||Prior Stroke or TIA||2|
|V||Vascular disease (atheroma)||1|
|A||Age 65 – 74 years||1|
A CHADSVASC score of 2 corresponds to an annualised stroke risk of >2%.
The following treatment strategies are recommended taking into account potential contraindications to the recommended drugs:
|CHADSVASC Score||Risk||Anticoagulation Therapy
|1||Low - Mid||Asprin|
|>=2||Moderate to High||*OAC|
*OAC = Oral Anticoagulant medication, most commonly Warfarin, but also includes newer medications such as Dabigatran (Pradaxa), Rivaroxaban (Xarelto) and Apixaban (Eliquis).
It is not true that the more atrial fibrillation you have then the higher the risk of stroke. A person who has only a few episodes per year can still have a stroke, whereas another person in "full-time" AF may not. Being in normal rhythm rather than AF does not necessarily reduce the risk of blood clots and stroke.
There are currently 2 options to prevent stroke for people with AF – "blood thinner" medications or a procedure to seal off the left atrial appendage. Recommended treatments vary according to a person's risk of stroke.
Do the treatments completely prevent stroke?
Less than one quarter of all strokes are caused by AF. In fact, the majority of strokes result from hardening of the arteries (atherosclerosis) leading to the brain and the effects of high blood pressure.
Different treatments are often required to lower the risk of stroke from these conditions. Although no treatment is 100% effective, patients with AF can significantly reduce their chances of having a stroke with appropriate therapy.
Blood thinners or "Anticoagulation" Treatments
"Blood thinner" medications act to generally reduce the body's ability to make blood clots and must be taken long term. People with no risk factors are generally recommended to take Aspirin (or an alternative such as Clopidogrel).
People with more than one risk factor need greater protection and a range of stronger medications for preventing blood clot formation (called oral "anticoagulation" treatments) may be recommended. Until recently warfarin was the only available anticoagulation tablet treatment. Warfarin requires careful monitoring with regular blood tests to keep the levels within a satisfactory range. Some of the other anticoagulation treatments now available in Australia are Pradaxa® (dabigatran), Xarelto® (rivaroxaban) and Eliquis® (apixaban) which have also been shown to effectively prevent strokes when taken long-term.
Rarely patients may suffer from major internal bleeding while taking anticoagulation, although the chances of this are very low (1% per year) if the levels are well controlled. The decision to take long term anticoagulation should be discussed carefully with your doctor.
Left Atrial Appendage Occlusion Device Implant
Left atrial appendage occluder devices are an emerging alternative treatment to taking long term anticoagulation to prevent stroke (although not if you have rheumatic heart valve problems). This involves a keyhole catheterisation procedure to deliver a small "plug" inside the heart to seal off the blind-ending pocket (left atrial appendage) where blood clots are known to form. Once the plug has healed in properly (around 2 months) then anticoagulation can be stopped. In the future, these devices may be a suitable option for people who are completely contraindicated for anticoagulation treatments. There is, of course, a small "upfront" risk of having a complication with the procedure of around 1-2%, which includes having major bleeding, or a stroke.
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