Atrial Fibrillation (AF)
What is atrial fibrillation (AF)?
AF is an abnormal heart rhythm. AF is caused by an “electrical storm” in the atria (the atria are the 2 upper chambers of the heart). AF causes the heart to beat rapidly and irregularly. The heartbeat is inefficient during AF and so the heart does not function as well as it does it a normal rhythm. In AF the walls of the atria do not contract in a coordinated fashion – the walls “wobble” rather than contract. This can lead to clots forming in the atria. These clots can break off from the wall of the atrium and lodge in the brain causing a stroke.
What are the symptoms of atrial fibrillation?
AF can cause tiredness, shortness of breath and chest pain. Some, but not all patients are aware of a rapid heartbeat during periods of AF.
What causes atrial fibrillation?
AF can be caused by high blood pressure, an overactive thyroid gland, sleep apnoea, being overweight, or almost any type of heart disease. In some patients there is no obvious cause for AF and this is called “lone” AF or “idiopathic” AF.
Is atrial fibrillation dangerous?
AF can have serious consequences: prolonged rapid beating of the heart can cause the heart to pump inefficiently causing fluid to accumulate in the abdomen, lungs or in the lower limbs (known as heart failure). AF also increases the risk of stroke. However, in most cases, the bad effects of AF can be minimised with medication.
How long do attacks of atrial fibrillation last?
The duration of attacks is variable. In some patients attacks terminate spontaneously after minutes, hours, days or weeks. This is called “paroxysmal AF.” In other patients, attacks last until the attack is treated with medication or an electric shock (known as electrical cardioversion) – this is called “persistent AF.”
What brings on attacks of atrial fibrillation?
In most cases attacks of AF occur randomly and cannot be predicted. However, in some patients attacks may occur during sleep, following surgery or infections (such as pneumonia) and occasionally by unusual stimuli such as drinking cold liquids.
Will atrial fibrillation get better without treatment?
Attacks of AF tend to occur more frequently and last longer as patients get older. In some patients there may be long intervals between attacks, even several years. Many (but not all) patients require medication to control attacks of atrial fibrillation.
What treatments are available for atrial fibrillation?
Conditions which contribute to AF should be controlled: high blood pressure, sleep apnoea, thyroid overactivity and heart valve problems should be treated.
- Medications may help prevent attacks of AF (see below). In some patients in whom it is not possible to stop AF, medications may be used to stop the heart from beating too quickly; for example: diltiazem (trade names: Cardizem, Vasocardol), verapamil (trade names Isoptin, Cordilox), beta-blockers (trade names: Tenormin, Noten, Betaloc, Lopressor, Minax, Bicor)
- Catheter ablation (pulmonary vein isolation) – see below
- In some patients in whom the AF cannot be controlled with medication and in whom catheter ablation is not appropriate, the best treatment may be AV nodal ablation (see below & additional patient information sheet)
Lifestyle modification is very important in the control of atrial fibrillation. Studies have shown that atrial fibrillation can be significantly improved by weight loss. Avoidance of excessive alcohol intake is also important. Obstructive sleep apnoea can cause or worsen atrial fibrillation so it’s important to get checked for this condition.
Can medication control atrial fibrillation?
Medications can be used to prevent attacks of AF but these medications are not always effective. Some of the drugs used to prevent AF include sotalol (trade names Sotacor, Solavert, Cardol), amiodarone (trade names Aratac, Cordarone, Cardinorm, Rithmik) and flecainide (trade names Tambocor, Flecatabs).
AV Nodal Ablation:
In some patients atrial fibrillation cannot be cured. If medical therapy does not control the heart rate, the best option might be to intentionally destroy the heart’s electrical wiring to prevent it from beating too fast. If this is done, it is necessary to implant a pacemaker to increase the heart rate in the lower chambers of the heart.
What is catheter ablation (pulmonary vein isolation)?
Catheter ablation is a technique for curing atrial fibrillation. The procedure is performed in hospital under general anaesthetic (in other words patients are “asleep” during the procedure). During this procedure thin tubes containing wires are inserted into the veins in the groin and passed up the veins to the heart. An X-ray machine is used to guide the placement of catheters.
The aim of this technique is to destroy muscle fibres which trigger atrial fibrillation. These fibres are located in the pulmonary veins (the veins that carry the blood from the lungs to the heart). Two techniques are used, cryoablation which involves freezing the fibres and radiofrequency ablation which uses electrical energy to destroy the fibres (like cautery). The success rate of these procedures depends on many factors. For paroxysmal atrial fibrillation (atrial fibrillation that starts and stops spontaneously) the success rate approaches 90% but approximately one third of patients will require more than one procedure to achieve this success rate. In longstanding atrial fibrillation the chances of cure are less than 90%. In patients who have had atrial fibrillation for a long time it may not be possible to perform successful catheter ablation.
How long does the catheter ablation (pulmonary vein isolation) take?
Most procedures take 2-3 hours. However patients are observed in a recovery room for 1-2 hours afterwards and so the patient may be away from his or her room for 4-5 hours.
What are the potential complications of catheter ablation?
The cryoablation technique:
The risk of cryoablation include: 1 in 200-300 risk of stroke, 1 in 1000 risk of death or heart attack, 2-3 chances in 100 of bleeding, infection, thrombosis or damage to the nerves or blood vessels, and 1 in 200 risk of paralysing the nerve to the right side of the diaphragm (phrenic nerve palsy). Fortunately, phrenic nerve palsy usually recovers spontaneously but this may take weeks or months. Some patients with phrenic nerve palsy have no symptoms whereas others feel short of breath. The risk of perforating the oesophagus (“food pipe”) is about 1 in 1000-5000. It is uncertain whether this technique can cause narrowing of the pulmonary veins but this risk is probably less than 1 on 500.
The risks of radiofrequency ablation include: 1 in 200-300 risk of stroke, 1 in 1000 risk of death or heart attack, 1 in 200 risk of narrowing the pulmonary veins, 2-3 chances in 100 of bleeding, infection, thrombosis or damaging the nerves or blood vessels and 1 in 1000 risk of atrio-oesophageal fistula (the creating of a hole between the atrium and the “food pipe”). The risk of perforating the “food pipe” if a transoesophageal echocardiogram is performed to check for clots in the heart is very low (about 1 in 1000-5000).
Is there much discomfort following the catheter ablation procedure?
Discomfort is usually minor. Some patients experience a sore throat caused by the breathing tube inserted by the anaesthetist. Some patients experience nausea after the anaesthetic. The wounds in the groin may be uncomfortable but pain is unusual. Some patients develop minor chest discomfort. A cough may develop following cryoablation.
How long are patients hospitalised for catheter ablation?
Patients usually stay in hospital for 1-2 nights.
How long will I be unable to work following catheter ablation?
Usually patients require approximately one week off work but this may be longer if work involves heavy manual tasks. Patients with sedentary occupations may be able to return to work after 3-4 days.
Do I need to stop warfarin or other blood thinners prior to catheter ablation?
In most cases warfarin is not stopped for the procedure. However it is important that the INR is less than 3.0 at the time of the procedure. The INR should be checked 2 days prior to the procedure the result discussed with Dr McGuire. Aspririn (Disprin, Cartia, Cardiprin) should not be stopped for the procedure. Dabigatran (Pradaxa), rivaroxaban (Xarelto) and Apixaban (Eliquis) must be stopped 48 hours prior to the procedure.
How long will I need to take “blood thinners” after the procedure?
This depends on individual patients. In many patients the “blood thinner” can be stopped after six weeks but in some patients it must be continued indefinitely.
Dr Mark McGuire
Cardiologist: Royal Prince Alfred, Mater Hospital, Prince of Wales Hospital and Prince of Wales Private Hospital.
Clinical Professor, University of Sydney