What is atrial fibrillation?
Atrial fibrillation (AF) is a form of arrhythmia or heart rhythm disorder characterised by an irregular heartbeat. It occurs due to problems with the heart’s electrical activity and can cause symptoms such as palpitations, dizziness, breathlessness and fatigue. Symptoms for some can be highly intrusive and impact on quality of life, whereas for others AF does not cause any symptoms at all and the diagnosis is only made after routine health checks, or tests carried out for other reasons. AF is a major risk factor for stroke, so getting it properly diagnosed and treated is very important.
What causes atrial fibrillation?
AF is very common, and one in four people will develop it at some point. An estimated 1.5 million people across the UK and over 16 million people worldwide are affected. Although it is not always clear why some people develop AF, there are a number of recognised risk factors. The biggest factor is age, with the majority of people diagnosed with AF being over 65 (although younger people can develop it too). A family history of AF is also being increasingly recognised as a risk factor, as well as those with certain pre-existing conditions, such as high blood pressure, diabetes, an overactive thyroid, obstructive sleep apnoea and other heart conditions. Lifestyle factors, such as being overweight, smoking and drinking too much alcohol also increase the risk of developing AF. AF can occur as brief episodes (paroxysmal AF) or be constant (persistent AF) and it is possible for paroxysmal AF to progress into persistent AF over time.
AF occurs due to problems with the heart’s electrical conduction system, which regulates the heartbeat and keeps the heart functioning normally. In people with AF, the electrical system in the heart’s upper left chamber (left atrium) becomes disrupted leading to an erratic heart rhythm which in-turn can lead to blood pooling in the upper chambers of the heart and increasing the risk of stroke.
Types of atrial fibrillation:
- Paroxysmal: For some patients atrial fibrillation occurs intermittently. Symptoms may come and go, only lasting for a few minutes to hours before stopping spontaneously.
- Persistent: For some patients atrial fibrillation does not go back to a normal rhythm on its own and they may require an electrical shock (cardioversion) or heart rhythm stabilising medications to restore it.
- Long-standing persistent: If atrial fibrillation continues for over one year, it is referred to as long-standing persistent.
- Permanent: For some patients accepting atrial fibrillation for the long-term is appropriate. In this situation the abnormal heart rhythm cannot be restored and the focus of treatment is to keep the heart rate under good control with medications as well as to address stroke risk.
How is atrial fibrillation diagnosed?
Diagnosing AF can be straightforward and may be detected by the presence of an irregular pulse (although not always, if the AF is episodic). Your doctor will start by talking through symptoms and your general health before recommending tests to confirm the diagnosis. Further tests are individualised but may include:
- Blood Tests – to exclude reversible causes
- Electrogram (ECG) – an electrical trace of the heart
- Echocardiogram – an ultrasound scan of the heart
- A heart monitor (for between 24-hours and up to two weeks) to wear at home
- Screening for obstructive sleep apnoea
How is atrial fibrillation treated?
AF is a major risk factor for stroke. Every 15 seconds, someone suffers an AF-related stroke, and these are often debilitating with higher mortality rates. The good news is AF-related strokes are largely preventable if AF is diagnosed and the risk is appropriately assessed and addressed. The risk is assessed on an individual basis with effective treatments (anticoagulants or ‘blood thinners’) available. Additional treatments are also available to help treat the symptoms associated with AF, with medication usually used as the first-line option.
Decreasing stroke risk
Atrial fibrillation is associated with blood clots forming in the heart which can become dislodged and transmitted into the blood vessels which supply blood to the brain, resulting in a stroke. The risk of stroke can be assessed on an individual basis and is determined by risk factors such as:
Congestive Heart Failure
Stroke, or previous transient ischaemic attack (TIA or mini-strokes which fully resolve)
Vascular Disease (such as previous heart attack, peripheral vascular disease)
These risk factors may be summarized as the CHA2DS2VASc score, and allows your doctor to assess your overall risk and to determine whether you should be started on anticoagulant medication.
Preventing blood clots by using anticoagulants
Your doctor may prescribe anticoagulants or ‘blood thinners’.
- Warfarin (Coumadin) is the oldest drug to avoid blood clots. Regular blood monitoring to check levels (INR – International Normalised Ratio) is advised to keep the levels well-controlled.
- Apixaban (Eliquis), Dabigatran (Pradaxa), Rivaroxaban (Xarelto), and Edoxaban (Lixiana) are termed Direct Oral Anticoagulants (DOACs) and are newer agents which have been introduced to replace warfarin. The immediate advantage of these is that they can be prescribed without the need for regular blood test monitoring, although they have similar effectiveness and bleeding risks as warfarin. These agents have proven to be useful alternatives to warfarin and may be recommended by your doctor.
Other treatment options for atrial fibrillation:
Lifestyle factors and managing other conditions
Addressing lifestyle factors can be very important in controlling AF. This might include weight loss, stopping smoking or reducing alcohol intake for some. Treatment for co-existing conditions such as high blood pressure, diabetes and obstructive sleep apnoea can also help to reduce the overall burden of AF.
In patients with persistent AF, an electrical cardioversion may be useful. This involves delivering a small electrical shock through the heart, with a view to stunning the heart back into a normal rhythm. This is done using pads applied to the chest under a light general anaesthetic. The procedure is very quick and safe and takes a few minutes. However, it is unlikely be a long-term treatment and most patients will revert to AF eventually.
Pulmonary vein isolation – Radiofrequency ablation / Cryoablation
An ablation procedure is a minimally invasive surgical procedure that can vastly improve AF symptoms and is particularly useful for patients with severe symptoms, or when medication alone is not controlling matters.
The procedure involves passing very fine catheters (wires) through a vein at the top of the leg into the heart. Electrodes at the tip of the wires can be used to identify electrical signals within the heart and to deliver radiofrequency ablation (heat) or cryoablation (freezing) to target the triggers for AF. The extra electrical signals that trigger AF are found within four pulmonary veins that carry blood from the lungs back to the left atrium. Pulmonary vein isolation is a technique where energy is used to destroy this small area of tissue that generates AF and by doing so generating scar tissue which blocks the extra electrical signals from the pulmonary veins reaching the left atrium. This process is repeated around the opening of each of the four pulmonary veins and can performed under a local anaesthetic with sedation or under general anaesthetic.
Some people with AF may eventually benefit from having a pacemaker fitted to regulate the heartbeat.