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.

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

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. 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.

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.

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.

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).

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.

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 consultant. 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.
  • 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.
  • 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 consultant 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