Heart conditions - atrial fibrillation

Atrial fibrillation (AF) is a type of arrhythmia, which means the heart beats in an irregular way. It is caused by a disturbance of the electrical messages that control the steady rhythm we know as the heartbeat. AF is the most common arrhythmia among those that last longer than a few seconds.

Overall, AF affects around two in every 100 people. It is uncommon in people under the age of 50 (less than 1 per cent) but common in people over the age of 75 (around 10 per cent of people in this age group are affected). Symptoms are not always obvious, but they may include palpitations or a fluttering heartbeat, an irregular heartbeat, chest pain, dizziness and fainting spells.

Treatment matters even when AF causes no symptoms, because the increased risk of stroke is present whether or not symptoms are felt.

How the heart’s rhythm normally works#

Normally, the heart’s electrical system causes its chambers to contract and relax in a steady rhythm. Electrical messages start in the heart’s two top chambers (the atria), in an area called the sinus node, which acts as the heart’s natural pacemaker.

These messages pass from the sinus node to another area called the atrioventricular node, which signals the two bottom chambers (the ventricles) to contract.

In AF, a problem affecting the sinus node causes the atria to twitch or quiver rather than contract properly. This distorts the messages reaching the atrioventricular node and makes the ventricles contract in a fast, irregular way. As a result, the heart pumps less efficiently and is more likely to form blood clots that can travel to the brain.

Symptoms of atrial fibrillation#

Atrial fibrillation often has no obvious symptoms and can go undetected for long periods. When symptoms do occur, they may include:

• a fluttering heartbeat (palpitations)
• an irregular heartbeat, which may be noticed when checking the pulse
• chest pain
• a general feeling of being unwell
• dizziness
• fainting spells
• difficulty tolerating exercise

Types of AF#

There are three main patterns of AF:

• a single episode of irregular beating (sometimes brought on by excessive alcohol intake)
• repeated episodes of irregular beating that last for short periods, known as paroxysmal AF
• irregular beating all the time, known as permanent, sustained or chronic AF

More persistent types of AF carry a higher risk of stroke.

AF and stroke#

A stroke can occur when an artery in the brain is blocked by a blood clot (an embolus).

People with AF are at greater risk of stroke because the irregularly beating atria are prone to forming blood clots. When the atria do not contract fully, blood can pool, stagnate and clot. A clot can break free, travel through the bloodstream and lodge in a blood vessel in the brain.

Left untreated, the risk of stroke is high. Other risk factors such as diabetes, high blood pressure or a previous stroke raise the risk further. AF also increases the risk of other heart problems, particularly heart failure.

Causes of AF#

AF is often triggered by another long-term illness or by an event that irritates the heart. Known causes and contributing factors include:

• long-term high blood pressure (hypertension)
• heart valve diseases that interfere with blood flow in the heart
• heart failure
• an overactive thyroid gland (hyperthyroidism)
• sleep apnoea
• chest surgery or chest trauma
• excessive intake of alcohol or other recreational drugs
• certain prescribed medicines
• some illnesses, such as pneumonia
• obesity
• lack of exercise, or extreme exercise

Sometimes no single cause can be identified. The chance of developing AF rises with age, as the heart itself ages, even without the risk factors above.

Diagnosis of AF#

Tests used to diagnose AF may include:

• a physical examination and medical history
• an electrocardiogram (ECG), a graph of the heart’s electrical activity
• a Holter monitor, a portable device that records the heart’s electrical activity over a longer period (for example, 24 hours)
• an echocardiogram, a special ultrasound of the heart
• blood tests

Treatment for AF#

Medicines to reduce the risk of stroke#

Anticoagulant medicines (blood thinners) are the most important part of AF treatment. They significantly reduce the risk of stroke and are the only therapies shown to prevent serious events and prolong life.

The term “blood thinners” is sometimes also used for medicines such as aspirin and clopidogrel, but these are ineffective at reducing stroke risk in AF and should not be prescribed for that purpose alone.

The effective anticoagulants for AF are warfarin and the newer warfarin-like medicines known as non-vitamin K oral anticoagulants (NOACs), which include dabigatran, apixaban and rivaroxaban. There is little difference between them in effectiveness, and the small differences can be discussed with your doctor.

All anticoagulants carry a risk of bleeding, including serious bleeding. This means they can occasionally cause strokes as well as prevent them, although the benefits usually outweigh the risks. The decision to use anticoagulation should weigh these benefits and risks carefully. Factors used to estimate stroke risk include a previous stroke, heart failure, high blood pressure, age, sex, diabetes and vascular disease.

Medicines to control the heart’s rhythm and rate#

Medicines used to restore a normal rhythm (anti-arrhythmic agents) include sotalol, flecainide and amiodarone. These may be given as injections or tablets. Because some of these medicines can cause toxicity, regular tests of liver and thyroid function may be needed.

Medicines used to slow the heart rate include beta-blockers (such as atenolol and metoprolol), some calcium channel blockers (diltiazem and verapamil) and digoxin.

Electric shock therapy (cardioversion)#

Given under general anaesthetic, a controlled electrical shock to the chest can help reset the heart’s electrical system. Long-term medication may still be needed afterwards to keep the heart beating normally.

Surgery for AF#

Most people with AF respond to non-surgical treatment. Severe cases that do not respond to medicines or cardioversion may need a procedure such as:

• Catheter ablation. A thin tube (catheter) is inserted into a main blood vessel in the upper thigh or groin and guided up to the heart. An electrode at the tip is activated, and radiofrequency energy destroys the small area of heart tissue responsible for the AF.
• Maze procedure. This is similar to catheter ablation but creates a pattern of small scars that traps the source of the abnormal rhythm and allows the sinus node to take control again. It is most often done as part of cardiac surgery performed for other reasons.

Lifestyle changes with AF#

AF is strongly linked with high blood pressure, inactivity and obesity. Lifestyle changes can help prevent and manage AF and reduce the risk of further health problems. Your doctor may suggest that you:

• take steps to control high blood pressure
• lose weight if needed
• reduce alcohol consumption
• exercise regularly
• aim to keep diabetes well controlled
• quit smoking

Key points#

• AF is the most common arrhythmia of those that last more than a few seconds.
• Treatment is important even when AF causes no symptoms.
• The increased risk of stroke is present whether or not a person has symptoms of AF.
• Normally, the heart’s electrical system makes its chambers contract and relax in a steady rhythm.
• In AF, the atria quiver instead of contracting, disrupting that rhythm.

Where to get help#