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Arrhythmia (irregular heart rhythm)


Expert reviewer, Dr Matthew Wright, Consultant Cardiologist and Electrophysiologist
Next review due June 2020

Arrhythmia is when your heart is beating too fast, too slow, or with an irregular pattern. For most people, arrhythmias aren’t anything to worry about, but some types can be serious.

How your heart works

Your heart pumps oxygen-rich blood all around your body through a network of blood vessels, called arteries, to your organs, muscles and nerves. It has four chambers – two at the top called the atria, and two at the bottom called the ventricles.

Watch our animation to see how your heart works:

How your heart beats

An electrical system controls your heart and tells it when to beat and push blood around your body.

Watch our animation to see how your heart beats:


When everything is working well, your heart will usually beat between 60 and 100 times a minute when you’re resting. But it can beat faster or slower than this. For example, it can beat faster when you’re exercising or are stressed, while it can beat slower if you’re young and athletic and have a naturally lower rate.

Changes in heart rhythm (arrhythmias)

Any interruption in your heart’s electrical system can cause an arrhythmia. This could happen if there’s a problem in the generation or conduction of these electrical impulses, or both. And this can happen for lots of reasons: everything from problems with the structure or function of your heart, to imbalanced hormones (your body’s natural chemicals) and from taking certain medicines.

If your heart beats too quickly, it’s called tachycardia, whereas if it beats too slowly, it’s called bradycardia. This might not be a problem, or it can be for some. If you have arrhythmia, your heart may beat either regularly or irregularly too. All this can affect how well your heart pumps blood around your body.

Types of arrhythmia

There are different types of arrhythmia; some, such as ectopic beats, are ‘benign’. These are when your heart feels like it’s missed a beat or thumped suddenly and are unlikely to cause you any harm. You can find out more about ectopic beats in our FAQ: Ectopic heartbeat below. Other types of arrhythmias include:

  • atrial fibrillation
  • atrial flutter
  • supraventricular tachycardia
  • ventricular tachycardia
  • ventricular fibrillation
  • heart block
  • sick sinus syndrome

Some are more serious than others. We have more information about each of them below.

Atrial fibrillation

Atrial fibrillation is the most common type of arrhythmia. When it happens, you might notice that your heartbeat feels irregular, and it may feel faster than usual. For more information, including other symptoms, see our topic: Atrial fibrillation.

Atrial flutter

Atrial flutter is similar to atrial fibrillation but what happens is slightly different, as is the way it’s treated. In atrial flutter, the electrical impulses that tell your heart when to beat form a smaller circuit in the top chambers of your heart (your atria). They beat much faster than they should, but the bottom chambers of your heart (your ventricles) can’t pump this fast. So, your atria and ventricles beat at different speeds, putting your heart under strain.

Supraventricular tachycardia

Supraventricular tachycardia (SVT) can make your heart beat really quickly – it may beat between 140 and 250 beats per minute. Attacks of SVT often come and go spontaneously. For more information about the symptoms, causes and treatments of this type of arrhythmia, see our topic: Supraventricular tachycardia (SVT).

Ventricular tachycardia

If you have ventricular tachycardia, your heart can beat faster, and it can sometimes develop into ventricular fibrillation (see below). This can be life threatening and can therefore be the most dangerous type of arrhythmia, although not for everybody. Most people with ventricular tachycardia already have some problems with their heart, but (rarely) some people get ventricular tachycardia even though their heart’s healthy. You can read more in our topic: Ventricular tachycardia.

Ventricular fibrillation

Ventricular fibrillation happens when electrical signals fire off in different areas of your ventricles at the same time. It’s an extremely fast, life-threatening heart rhythm that results in your heart being unable to beat properly; so little (or no) blood is pumped out of your heart. If you have ventricular fibrillation, you’ll quickly lose consciousness and you may have a cardiac arrest. It’s normally fatal unless you get treatment immediately. This starts with cardiopulmonary resuscitation (CPR). You can see how this is done in our animation: How cardiopulmonary resuscitation (CPR) is carried out.

Heart block

If you have heart block, your heart beats more slowly. Sometimes heart block doesn’t cause any problems, but if it’s more serious, you might get symptoms such as dizziness, or you can even black out. To learn more, see our topic on Heart block.

Sick sinus syndrome

If you have sick sinus syndrome, your sinoatrial node, which generates the electric pulses in your heart, doesn’t work properly. Around half of people get a type of sick sinus syndrome called tachy-brady syndrome. This causes your heart to beat slowly at first, and then fast. You might not get any symptoms, but if you do, you might feel dizzy and you might even collapse.

Diagnosis of arrhythmia

If you’re unsure about any symptoms you’re having, it’s best to talk them through with your GP. Our Cardiology Clinical Adviser, Dr Yassir Javaid, explains why in our video: When should you see a doctor about your heart?

Your GP will ask about your symptoms and medical history. They’ll examine you, checking your pulse and blood pressure too. Your GP might refer you to see a cardiologist – a doctor who specialises in identifying and treating heart conditions. Or they might send you to hospital straightaway for tests.

You might need to have one or more of the following tests to see if you have an arrhythmia.

  • Blood tests. These can test for substances in your blood, such as potassium and calcium, and to check if your thyroid is working as it should.
  • Electrocardiogram (ECG). This records the electrical activity of your heart to see how well it’s working. 
  • 24-hour heart monitor (ambulatory ECG). This records the electrical activity of your heart while you go about your usual activities over 24 hours (or longer if necessary).
  • Exercise ECG (cardiac stress test). This is when you have an ECG while you exercise to see how your heart works under pressure. It may trigger abnormal heart rhythms, but you're in the best place for this to happen as you'll be surrounded by a medical team.
  • Echocardiogram or transthoracic echocardiogram. These use ultrasound (sound waves) to produce a clear image of your heart muscles and valves to see how well it’s working.
  • Tilt table test. In this test, you'll lie down on a table, which will be tilted upwards. A technician will measure your heart rate, rhythm and blood pressure at different points.
  • Electrophysiology study. This checks the electrical activity of your heart to see what’s causing an abnormal heart rhythm.

Treatment of arrhythmia

If your arrhythmia is caused by an underlying health condition, your doctor will focus your treatment on that. Treatment will depend on the type of arrhythmia you have and may include:

  • self-help measures, such as exercising and cutting back on anything that triggers an arrhythmia, such as alcohol or caffeine, and not taking drugs, such as cocaine
  • medicines – some medicines stop an arrhythmia, while others can prevent them happening
  • a cardioversion, which is a procedure that uses an electrical shock to restore your normal heart rhythm
  • a pacemaker, which is a small device that’s implanted under your skin of your chest to regulate your heart beat
  • an implantable cardioverter defibrillator (ICD), which can monitor your heart rhythm and deliver an electric shock to correct your heartbeat if it detects a problem
  • catheter ablation therapy, in which your doctor destroys tissue in the area of your heart that’s causing the abnormal rhythm

You can find out more about specific treatments for different types of arrhythmias on our arrhythmia topic pages, including:

Frequently asked questions

  • If you think a prescription medicine is affecting your heart rate, don’t stop taking it without speaking to your GP first. If you’re taking an over-the-counter medicine, ask your pharmacist for advice.

    You might get an arrhythmia if you take certain prescription medicines, such as:


    Over-the-counter medicines that act as stimulants can also cause palpitations (a thumping in your chest), such as:

    • antihistamines that are used to treat hay fever
    • decongestants in cough and cold medicines
    • some herbal and nutritional supplements

    Always read the patient information leaflet that comes with your medicine. If you think your medicine is causing an arrhythmia or making it worse, speak to your pharmacist or GP for advice.

  • The rules depend on the type of arrhythmia you have, how well it’s controlled and the type of vehicle you want to drive. It’s essential that you don’t drive until your arrhythmia is under control so you don’t put yourself or others in danger.

    As long as you don’t have any symptoms that could distract you when driving, you’ll probably be able to drive a car or motorcycle. But the cause of your arrhythmia must have been identified and your condition controlled for at least four weeks. Ask your doctor if they agree that your condition is controlled.

    If you have symptoms, such as dizziness or breathlessness, you shouldn’t drive and you should let the Driver and Vehicle Licensing Agency (DVLA) know. See your doctor for advice as you might be able to try another treatment to control your symptoms.

    If you’ve had a procedure to treat your arrhythmia, you won’t be able to drive for longer. This can range from a couple of days to several months depending on the treatment you have.

    The rules about driving are different if you have an arrhythmia and drive a lorry, or are responsible for passengers. For example, you won’t be allowed to drive a lorry or bus if your heart function is below a certain level.

    If you’re in any doubt about driving, always follow your doctor’s advice and check the DVLA website.

  • If your heart has missed a beat or thumped suddenly, it’s likely to be an ectopic heartbeat. Ectopic beats are very common and are generally completely harmless. You don’t usually need any treatment. But occasionally, if they happen a lot, they can be a sign of a more serious condition, such as structural problems with your heart.

    If your ectopic beats happen a lot, or are troublesome, your GP may refer you to see a cardiologist. A cardiologist is a doctor who specialises in identifying and treating heart conditions.


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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, June 2017
    Expert reviewer, Dr Matthew Wright, Consultant Cardiologist and Electrophysiologist
    Next review due June 2020



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