Overview
Heart arrhythmias are abnormal heart rhythms where the heart beats too fast (tachycardia), too slow (bradycardia), or in an irregular pattern. Atrial fibrillation (AF) is the most common significant arrhythmia. Some arrhythmias are harmless; others can cause stroke, heart failure, or cardiac arrest.
How common is it?
Atrial fibrillation is a common heart rhythm problem and becomes more likely with age. Other arrhythmias can occur at any age.
Causes and risk factors
Arrhythmias arise from abnormalities in the heart's electrical conduction system. Many result from underlying heart disease but some occur in otherwise healthy hearts.
Common risk factors
- High blood pressure (the most important modifiable risk factor for AF)
- Coronary artery disease
- Heart valve disease
- Thyroid overactivity
- Alcohol excess ('holiday heart syndrome')
- Sleep apnoea
- Age
- Obesity
Symptoms
- Palpitations: racing, fluttering, or irregular heartbeat sensation
- Breathlessness
- Dizziness or light-headedness
- Chest discomfort
- Fatigue
- Fainting (more serious arrhythmias)
- Some people with AF have no symptoms
When to see a doctor
Call your local emergency number if palpitations do not go away or occur with chest pain, shortness of breath, fainting or feeling faint. Do not drive yourself. If those symptoms have stopped, seek urgent medical assessment. Arrange a review for recurrent or increasingly frequent palpitations, especially with a known heart condition.
Diagnosis
ECG during symptoms is diagnostic. 24 to 72-hour Holter monitor or 2-week event recorder captures intermittent arrhythmias. Echocardiogram assesses cardiac structure. Thyroid function blood test excludes thyroid cause.
Treatments
Rate or rhythm control medication
Beta-blockers, digoxin, and calcium channel blockers control the rate in AF. Antiarrhythmic drugs (flecainide, amiodarone) restore and maintain normal rhythm.
Anticoagulation
Anticoagulants reduce stroke risk in people with AF who are likely to benefit. The clinician weighs stroke risk against bleeding risk and considers kidney function, valve disease and other medicines. NICE uses CHA2DS2-VASc to assess stroke risk. Not every arrhythmia or every person with AF needs anticoagulation.
Catheter ablation
A procedure using radiofrequency or cryotherapy energy delivered through catheters to destroy the abnormal electrical pathways or triggers causing the arrhythmia. Increasingly effective for paroxysmal AF.
Self-care and lifestyle
- Control blood pressure as it is the most important modifiable risk factor for AF
- Reduce or eliminate alcohol as even moderate intake increases AF risk
- Treat sleep apnoea which is a strong driver of AF recurrence
- Take anticoagulation medication consistently and have INR monitoring if on warfarin
Prevention
Treating high blood pressure, limiting alcohol, maintaining healthy weight, treating sleep apnoea, and staying active reduce the risk of developing AF and other arrhythmias.
Sources for targeted updates
Updated: 24 October 2026. Targeted corrections to frequency, urgent-care guidance, treatment, key facts. This update covers the named sections; a full review of the remaining guide is pending.