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An abnormal heart rhythm – rapid, slow and/or irregular – that is caused by disturbance in the heart’s electrical conduction system. Symptoms include: palpitations, breathlessness, light–headedness, dizziness or blackout, chest pain, angina. Rarely, some types of arrhythmia cause sudden death.

The heartbeat

  • Adults: normal heart rate (sinus rhythm) is 60–100 beats per minute (BPM) at rest.
  • Children:
Age (years) Heart rate (beats/min)
<1 110-160
1-2 100-150
2-5 94-140
5-12 80-120
12+ 60-100
  • Sinus bradycardia is a regular but slow heartbeat (<60 BPM)
  • Sinus tachycardia is a regular but fast heartbeat (>100 BPM).
  • Ectopic beats are extra heartbeats, common and usually normal.
  • Palpitations are an unpleasant awareness of the heartbeat – often described as ‘thumping in the chest’ – and can be quite normal.


Types of arrhythmia include:

  • Atrial fibrillation: common; the atrial muscles flicker and the ventricles contract irregularly.
  • Ventricular fibrillation: whole heart stops beating properly and just flutters; fatal unless heart is re-started with an electric shock from a defibrillator.
  • Atrial tachycardia and ventricular tachycardia: need urgent medical treatment.
  • Heart block: an abnormally slow beat caused by the heart’s electrical impulses not reaching the ventricles properly.

Atrial fibrillation (AF) The most common heart rhythm disturbance. AF affects about 10% of people over 65 years of age. The ventricles contract irregularly, and the atrial muscles flicker; blood pools in the atria, creating a risk of clot formation that predisposes to stroke. Persistent AF is managed with anticoagulation therapy.

AF Association

British Heart Foundation Atrial Fibrillation 

NICE NG196. Atrial fibrillation: diagnosis and management; 2021

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