Arrhythmia is an uncontrolled, disordered or irregular heartbeat. It may be faster or slower than usual.

By Wallace Health I Medically reviewed by Adrian Roberts.
Page last reviewed: October 2018 I Next review due: October 2023

What is a normal heartbeat?

Your heart is divided into four chambers. The two upper chambers are called the left and right atrium. The two lower chambers are called the left and right ventricle. In your right atrium sits a special group of cells called the sinus node — this is your heart's natural pacemaker and controls the rhythm of your heart.  

The sinus node controls your heart rhythm by producing electrical signals that trigger each heartbeat. These electrical signals make the muscles of your atria contract, which pumps blood into your ventricles. The electrical signals then arrive at another special group of cells that sit between the right atrium and right ventricle called the atrioventricular node (AV node). 

The AV node slows down the electrical signals so your ventricles have time to fill with blood. The electrical signals then continue on to your ventricles, which causes them to contract. The right ventricle can then pump blood to your lungs and the left ventricle pumps blood to the rest of your body. 

If your heart is healthy, this process causes you to have a heart rate of 60-100 beats per minute at rest. 

What is arrhythmia?

Every year, over two million people in the UK experience arrhythmia. However, most can lead a normal life if they are diagnosed and treated. 

Arrhythmia is when your heart beats in a disordered way. Instead of a steady rhythm, your heart may: 

  • Beat faster — this is called tachycardia ie a heartbeat faster than 100 beats per minute 
  • Beat slower — this is called bradycardia ie a heartbeat slower than 60 beats per minute
  • Miss beats

Arrhythmias can broadly be divided into ventricular arrhythmias, which start in your ventricles and supraventricular arrhythmias, which start above your ventricles ie in your atria or AV node.

Arrhythmias can also cause palpitations, which is when you can feel your heart beating loudly in your chest. These can be prolonged and accompanied by other symptoms, such as breathlessness, making it difficult to get on with everyday activities.

The most common reason for arrhythmia is that your heart’s internal pacemaker is not working normally. There are different types of arrhythmia. The most common is atrial fibrillation, an irregular and fast heart rhythm. It is often a sign of an underlying problem such as coronary heart disease.

Untreated arrhythmia increases your risk of heart attacks and strokes and can affect your everyday life.

Arrhythmia types

Tachycardias in the atria

Tachycardias in the atria, also known as supraventricular tachycardia, refers to different types of arrhythmia that all start in your atria or AV node. Symptoms include palpitations that start and end suddenly. Supraventricular tachycardias include: 

  • Atrial fibrillation — irregular electrical signals in your atria causing a rapid heart rate and uncoordinated, weak contractions of your atria and ventricles; atrial fibrillation sometimes stops on its own but other times won't stop without treatment; it can lead to complications, such as stroke
  • Atrial flutter — similar to atrial fibrillation but the electrical signals are less disorganised and less out of sync; it can lead to complications, such as stroke 
  • AV nodal reentrant tachycardia (AVNRT) — heart palpitations caused by an additional electrical pathway that goes through your AV node along which electrical signals can pass from your atria to your ventricles; it can cause fainting and/or heart failure
  • Premature atrial contractions — extra heartbeats that come early; these are usually harmless and do not need treatment
  • Wolff-Parkinson-White syndrome (WPW) — a rapid heart rate caused by an additional electrical pathway along which electrical signals can pass from your atria to your ventricles without passing through your AV node; this abnormal pathway is present from birth but may only cause symptoms as an adult

Tachycardias in the ventricles

Tachycardias in the ventricles, also known as ventricular tachycardia (v-tach), refers to different types of arrhythmia that all start in your ventricles. They cause a rapid, regular heart rate which prevents the ventricles from filling enough and consequently prevent blood from reaching the rest of your body efficiently.

If your heart is otherwise healthy, ventricular tachycardia may not cause major problems. However, if you have heart disease or a weak heart, ventricular tachycardia can be a medical emergency. Types of ventricular tachycardia include: 

  • Long QT syndrome — a heart condition where rapid, irregular heartbeats cause fainting; in some cases, where the heart rate becomes very erratic, it can cause sudden death; certain medications, congenital heart defects and a specific genetic mutation can cause long QT syndrome
  • Premature ventricular contractions (PVCs) — one of the most common arrhythmias, which makes you feel as if you have skipped a heartbeat
  • Ventricular fibrillation — rapid, irregular electrical signals in your ventricles causing your ventricles to quiver instead of properly contract to pump blood to your body; if a normal heart rhythm can't be restored within minutes of ventricular fibrillation, the condition is fatal; it is most common in those with underlying heart disease or after a major trauma

Bradycardia — a slow heartbeat

Bradycardia is defined as a heart rate of less than 60 beats per minute at rest. However, it is not always a problem. If you are in good health and normally have a resting heart rate of less than 60 beats per minute, your heart may simply be efficient ie able to pump enough blood to your lungs and the rest of your body even at a low heart rate. If you take certain medications (eg medication for high blood pressure), your heart rate may also be lower than usual. 

Bradycardia is, however, a problem if your heart is not able to pump enough blood to your lungs and the rest of your body. There are different types of bradycardia including sick sinus syndrome and conduction blocks.

Sick sinus syndrome occurs when your sinus node can't properly send out electrical signals. Signals are blocked, disrupted or slowed down. This can cause your heart rate to switch between too slow (bradycardia) and too fast (tachycardia). Sick sinus syndrome is more common in older adults and can be caused by scar tissue near the sinus node.

Conduction blocks occur when electrical signals running through your heart are blocked or slowed down. They can occur at any point along the electrical pathways that run through your heart, however, they usually occur in or near your AV node. If electrical signals are completely blocked, other cells in your AV node or ventricles can compensate by generating a steady but often slower heartbeat. Conduction blocks do not always cause symptoms. When they do, symptoms include skipped heartbeats or bradycardia.

Arrhythmia symptoms

A normal resting heart rate for an adult is around 60-100 beats per minute but will be higher if you’re exercising or excited.

From time to time, you might notice that your heart feels as though it is beating quickly, slowly or loudly. It might also miss a beat, which is called an ectopic beat. This is quite normal and there’s no reason to worry.

However, you should see a doctor if you have any of the following arrhythmia symptoms:

  • Anxiety and/or sweating
  • Breathlessness
  • Blurry vision, dizziness and/or fainting
  • Chest discomfort, pain, tightness and/or a pounding sensation
  • Fatigue, weakness and/or easily tiring
  • Frequent palpitations ie feeling as if you have skipped a heartbeat, a fluttering or flip-flop sensation

Talk to your doctor if you’re concerned about symptoms

You can book an appointment with a Spire private GP today.

Book an appointment

Arrhythmia causes

There are many causes of atrial fibrillation. Those that involve your heart include: 

  • Changes to the structure of your heart eg cardiomyopathy 
  • Coronary heart disease ie blockage of the arteries that supply your heart
  • Heart attack (myocardial infarction)
  • Heart valve problems
  • Scarring caused by a previous heart attack

Atrial fibrillation can also be caused by: 

  • Diabetes
  • High blood pressure
  • Infection with COVID-19
  • Overactive thyroid (hyperthyroidism) or underactive thyroid (hypothyroidism)
  • Sleep apnoea

Arrhythmia risk factors

Arrhythmia becomes more common as you get older. Other factors that increase your risk include: 

  • Air pollution or other environmental pollution
  • Anxiety or stress
  • Certain medical conditions — this includes:
    • Certain autoimmune disorders
    • Diabetes
    • High blood pressure
    • Low blood sugar
    • Obesity
    • Sleep apnoea
  • Certain medications (eg certain over-the-counter cold and allergy drugs) and nutritional supplements 
  • Drinking alcohol, smoking tobacco and using recreational drugs 
  • Family history — certain arrhythmias can run in families; you may therefore be at higher risk if you have a close relative with arrhythmia

Q & A

What is atrial fibrillation?

In this video, Dr David Fox, Consultant Cardiologist and Electrophysiologist, explains what atrial fibrillation is and what triggers the condition. He also discusses the causes and symptoms.

Diagnosis and tests for arrhythmia

If you have persistent arrhythmia symptoms or you have a family history of unexplained sudden death, see your GP. They will check for factors that could increase your risk of having a stroke as well as other related conditions, such as coronary heart disease, high blood pressure and valve disease.

They may ask about any family history of heart problems, as sometimes abnormal heart rhythms are inherited. They may also refer you to a doctor who specialises in treating heart disorders (a cardiologist). 

Your cardiologist may recommend an ECG (electrocardiogram) to check your heart rhythm and/or an ambulatory ECG, where you wear a Holter monitor to check your heart rhythm for 24-hours while you go about your daily activities. 

To help determine what kind of underlying condition is causing your symptoms, they may also recommend: 

Other tests that your cardiologist may recommend include: 

Cardiac catheterisation 

This is used to check your heart valves, coronary arteries, atria and ventricles. A long, thin tube (catheter) will be inserted into a vein in your leg or arm. Next, using an X-ray machine, the catheter will be guided to your heart. A special dye will be injected to visualise your heart structures and X-ray videos will be recorded.

Electrophysiology study 

This is used to record your heart's electrical activity and check its electrical pathways. Your doctor will trigger your arrhythmia in a safe and controlled manner and may then give you different medications to check which one best treats your arrhythmia. This type of study can also determine if a specific device or procedure may help.

Event recorder

If your symptoms are infrequent, your doctor may recommend wearing an event recorder for about a month. When you feel symptoms coming on, you press a button on the recorder, which will record your heart’s electrical activity for several minutes so your doctor can later examine the results.

Head-up tilt table test

If your symptoms include fainting, this test is used to determine if it is due to problems with your heart's electrical system, your nervous system or your blood vessels. You will lie down on a special table that will be tilted to different angles while you have an ECG and your blood pressure, oxygen levels and heart rate are monitored. 

Implantable loop recorder 

A small device is implanted just underneath your skin and will constantly record your heart’s electrical activity and send the data back to your doctor.

Stress tests 

These are used to check how much physical stress it takes before your heart presents a rhythm problem or you show symptoms of not getting enough blood pumped around your body. Most commonly, this involves walking on a treadmill or cycling on a stationary bike while the intensity is gradually increased. During this time you will have an ECG, and your heart rate and blood pressure will be monitored. 

Common treatments for arrhythmia

Your doctor may prescribe one or several of the following medications:

  • Anticoagulants to prevent blood clots and reduce the risk of a stroke or heart attack
  • Beta-blockers and/or calcium, potassium or sodium channel blockers to control your heart rate
  • Digoxin to slow down your heart rate 

They’ll also advise you about lifestyle changes you can make, such as eating healthily, losing weight and reducing how much alcohol and caffeine you drink.

If you have tachycardia, your doctor may also advise you on vagal manoeuvres. These techniques help relax your body and control your heart rate by affecting your vagus nerve. Vagal manoeuvres include: 

  • Cough or gagging
  • Holding your nose and strongly exhaling (Valsalva manoeuvre)
  • Lying down
  • Placing a cold, wet towel over your face

In an emergency eg if you present with severe heart rhythm symptoms in A&E, your doctor may inject you with adenosine or atropine. 


If medication does not control your arrhythmia, your doctor may recommend cardioversion. You will be placed under general anaesthetic and a doctor will apply electrical signals on your chest to correct your abnormal heart rhythm. This can be used to treat atrial fibrillation. 

Catheter ablation 

Catheter ablation surgery for heart arrhythmia involves passing a thin wire into your leg and guiding it into your heart. High-frequency electrical energy is then passed through the wire. This triggers an unusual rhythm in the area of tissue causing your faulty heart rhythm and neutralises this tissue to prevent your arrhythmia. 

Catheter ablation surgery is used to treat paroxysmal supraventricular tachycardia, atrial flutter and atrial fibrillation, as well as certain other types of atrial and ventricular tachycardias.

Surgery to implant an electrical device

Some arrhythmias can be treated by implanting a small electrical device to control your heartbeats, such as an implantable cardioverter defibrillator (ICD) or a pacemaker.


A pacemaker sends electrical signals to your heart muscle to regulate your heartbeat. A pacemaker contains a pulse generator, which contains a battery and a very small computer, and wires that send the electrical signals to your heart muscle.


An ICD  is usually used to treat life-threatening arrhythmias, such as ventricular tachycardia and ventricular fibrillation. The ICD continuously records your heart rhythm. If it detects a very fast, unusual rhythm, it sends an electric shock to your heart muscle. This triggers your heart to beat in a regular rhythm. Similarly to a pacemaker, an ICD contains a pulse generator and wires that deliver the electrical signals to your heart. 

There are three different types of ICD: biventricular ICD, dual-chamber and single-chamber. Your doctor can set several different programmes on your ICD including: 

  • Anti-bradycardia pacing — electrical signals to maintain a regular rhythm if your rhythm slows down too much
  • Anti-tachycardia pacing — a series of small electrical signals to restore a normal heart rate and rhythm
  • Cardioversion — a low-energy shock to restore a regular rhythm
  • Defibrillation — a higher-energy shock to restore a regular rhythm when your heartbeat is dangerously fast or irregular

Other heart surgeries for arrhythmia

If you have atrial fibrillation, your surgeon may recommend the maze procedure. This involves making a series or "maze" of cuts in your atria to keep your heart's electrical signals following certain pathways. You may still need a pacemaker implanted afterwards. 

Depending on the underlying cause of your arrhythmia, you may need other types of surgery to treat various heart conditions eg a coronary artery bypass to treat coronary heart disease. 

Complications of arrhythmias

An untreated arrhythmia can cause problems including: 

  • Dementia, including Alzheimer’s disease  — this may occur if your brain doesn’t get adequate blood supply over time 
  • Heart attack — ventricular fibrillation can stop your heart from beating
  • Heart failure — repeated arrhythmias can prevent your heart from pumping efficiently 
  • Stroke — blood that stays too long in your atria can clot; a clot can then travel to your brain and cause a stroke

Driving safely with arrhythmia

You must inform the Driver and Vehicle Licensing Agency (DVLA) if you have an arrhythmia that affects your driving eg an arrhythmia that causes you to faint. 

If you are not sure if your arrhythmia affects your driving, speak to your doctor. They will consider: 

  • The frequency of your arrhythmia symptoms
  • The severity of your arrhythmia
  • The type of arrhythmia you have
  • Your arrhythmia treatment

If you have no symptoms and you do not have a history of serious heart rhythm problems and/or your arrhythmia medication keeps your arrhythmia well-controlled, your doctor may say that you can drive. 

Arrhythmia prevention

Arrhythmias are not always preventable however making certain lifestyle changes can reduce your risk of developing further heart problems. This includes: 

  • Avoiding or limiting alcohol and caffeine in your diet
  • Maintaining a healthy blood pressure — this may involve eating a healthy diet, regularly exercising and taking any prescribed medication for high cholesterol or high blood pressure
  • Eating a healthy balanced diet, which includes lots of fruits and vegetables, whole grains, lean protein (eg white-fleshed fish) and plant-based proteins — avoid foods high in saturated or trans fats
  • Not smoking
  • Maintaining a healthy weight and exercising regularly
  • Reducing your stress levels

Also, make sure you attend regular check-ups with your doctor and keep them informed of any medications and supplements you are taking. If you get a cold, check with your doctor before you take any cough or cold medications as some can trigger arrhythmia. 

Frequently asked questions

Can asthma cause arrhythmia?

Asthma increases your risk of arrhythmia, specifically atrial fibrillation.

Can alcohol cause arrhythmia?

Drinking excessive amounts of alcohol can cause arrhythmias as well as increase your risk of other heart diseases, such as cardiomyopathy.

Can high cholesterol cause arrhythmia?

High cholesterol can cause heart disease, which increases your risk of developing arrhythmia.

Can low calcium cause arrhythmias?

Low calcium levels can put you at greater risk of developing arrhythmias, including sudden cardiac arrest.

How serious is a heart arrhythmia?

Most arrhythmias need treatment to prevent more serious complications from developing, such as stroke, heart failure or a heart attack. So although you may not have severe symptoms, it is still important to see your doctor if you experience symptoms of arrhythmia.