Arrhythmia is an abnormal heart rhythm. This could be your heart beating faster, irregularly, or slower. Your heart is controlled by electrical impulses which cause heartbeats. If there’s a problem with the conduction system, this can cause an arrhythmia. Most people who have abnormal heart rhythms are still able to live their lives as normal if they’ve been diagnosed properly.

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Understanding Arrhythmia

Symptoms of arrhythmia depend on what type of arrhythmia you have. You can learn more about some of the types below.

Atrial fibrillation or AF, is the most common type of arrhythmia, this is when the heart beats abnormally fast and beats irregularly. In some cases, the heart rate can be considerably higher than 100 beats per minute. It affects around 1.4 million people in the UK. It’s more common in older people, but it can affect adults of any age. AF is more likely to happen in people with other health conditions like:

• High blood pressure (hypertension)

• Atherosclerosis

• Heart valve problems 

It can also be triggered by:

• Drinking alcohol to excess

• Smoking

• Obesity 

Symptoms of AF include:

• An irregular heart rate

• A faster-than-usual heart rate 

• Dizziness

• Feeling short of breath

• Feeling tired

• Feeling noticeable heart palpitations

In some cases, AF doesn’t cause any symptoms and you might not know that your heart rate is irregular.

Make sure to speak to your GP or call 111 if:

• You have chest pain that comes and goes

• You have chest pain that doesn’t last, but you’re worried

• You have a sudden change in your heartbeat

• Your heart rate has been lower than 60 or above 100 regularly 

• You have any of the above and you have other symptoms like dizziness or shortness of breath

Call 999 if you have sudden chest pain and it:

• Spreads to your arms, neck, jaw or back

• Makes your chest feel heavy or tight

• Started with sweating, nausea, being sick or shortness of breath

• Continues for more than 15 minutes

The above symptoms could be a heart attack. Make sure to call 999 immediately as a heart attack is a medical emergency. If you have symptoms of arrhythmia or have a history of unexplained sudden death in your family, make sure to speak to your GP. They can refer you to a heart specialist (cardiologist) or an electrophysiologist who specialises in heart rhythm disorders. 

Supraventricular tachycardia (SVT) is a type of arrhythmia that causes an abnormally fast heart rate. An SVT can make the heart suddenly start beating quickly, then slow down quickly. These episodes can last for seconds, minutes or hours. In rare cases, they may even last for days. Your heart rate can reach as high as 250 beats per minute but it’s usually between 140-180 beats per minute.

SVT isn’t usually serious, but in some cases, you might need treatment. SVT attacks often happen for no obvious reason. However, they may be triggered by a change in posture, exertion, emotional upset, coffee or alcohol. If you have SVT, your heart muscle contracts so fast that it can’t relax between contractions. This means that the amount of blood being pumped around the body is reduced.

This causes symptoms such as:

• Dizziness 

• Heart palpitations 

• Shortness of breath

• Chest pain

• Light-headedness

• Feeling tired

In rare cases, people might faint as their blood pressure may drop. SVT can happen to anyone at any age, but it often happens for the first time in children and young adults. 

Having a slow heart rate is known as bradycardia. This is when your heart rate is below 60 beats per minute whilst resting. For some people who are very fit, like athletes, this can be normal. Bradycardia is most common in people over 65 years old and people who are physically fit. Symptoms of bradycardia may include:

• Feeling dizzy

• Feeling tired

• Fainting

• Chest pain

• Palpitations

• Struggling to concentrate

• Shortness of breath

Some people are born with bradycardia, but it can be caused by other factors like:

• Having had a heart attack

• Congenital heart problems 

• Certain medications


Cardiovascular disease like coronary heart disease

Bradycardia sometimes doesn’t have any symptoms and may not be a cause for concern particularly in those who are physically fit.

Heart block happens if there’s a problem with the flow of the electrical pulses that control how your heart beats. With heart block, the flow of electricity through the heart is either delayed or blocked at a point in the pathway. There are three main types of heart block:

• Atrioventricular (AV) heart block 

• Bundle branch block

• Tachybrady syndrome 

The cause of heart block depends on what type of heart block you have. Causes can include:

• Coronary heart disease, including heart attack

• Congenital heart disease 

• Some medicines

• Cardiomyopathy

• Heart muscle thickening 

• Some lung conditions

• Some medicines

Heart blocks can also happen naturally in a normal heart even if you don’t have a heart problem.

Atrioventricular (AV) heart blocks

An AV heart block is when the electrical impulses are delayed or blocked as they travel between the atria (top chambers of the heart) and the ventricles (the bottom chambers of the heart). There are different degrees of AV heart block:

• First-degree heart block – this doesn’t usually cause symptoms or need treating

• Second-degree heart block – this can cause symptoms in some cases which may require treatment 

• Third-degree heart block – this can be a medical emergency and is the most serious

In some cases, heart block can cause your heart rate to be very low. A first-degree AV heart block can become a higher-degree heart block if left untreated.

Bundle branch blocks 

A bundle branch block is when electrical impulses travel through the ventricles at a slower pace than usual. This happens because of a block in the pathway. This delay doesn’t usually cause any symptoms. A bundle branch block doesn’t normally need medical treatment, but if you have an underlying heart condition that’s causing a bundle branch block, you might need treatment for that.

There are two types of bundle branch blocks:

• Left bundle branch block – this could be the sign of a pre-existing heart condition that you may need treatment for

• Right bundle branch block – this can happen without a pre-existing heart condition but can also be caused by a pre-existing heart condition

Atrial flutter is an arrhythmia which makes the upper chambers of your heart (the atria) beat too quickly – it can reach around 300 beats per minute instead of 60-100. Atrial flutter can strain your heart as it means that your atria and ventricles are beating at different speeds. Some people with atrial flutter have no symptoms, but symptoms can include:

• Feeling short of breath

• Feeling tired 

• Having palpitations

• Feeling light-headed

• Having a tightness in your chest

• Fainting

If you have any of the above symptoms, make sure to speak to your GP, especially if you already have a pre-existing heart condition.

In some cases, people with atrial flutter often have a pre-existing heart or circulatory condition like:

• High blood pressure

• Coronary heart disease

• Having had heart surgery

• Congenital heart disease

• Having heart valve disease

In rare cases, atrial flutter can be caused by:

• Inflammation of the heart like myocarditis

• Cardiomyopathy (a disease of the heart muscle)

• Lung disease

• Hormonal conditions like an overactive thyroid

Sometimes atrial flutter can happen without there being a known cause. 

An arrhythmia can affect people of all ages, but it’s more common in older people and there are some risk factors which can increase your risk of developing one. These include:

• Drinking alcohol in excess over a long period of time

• Being overweight 

• If you’ve had a heart attack

• If you have heart failure

• If you’ve had severe COVID-19

• Having coronary heart disease

• Having a cardiomyopathy – this is a general term for diseases of the heart muscle. It can affect the way the heart pumps blood around the body

Common triggers for an arrhythmia include:

• Alcohol 

• Tobacco

• Viral illnesses like COVID-19 or flu

• Exercise

• A change in posture

• Caffeinated drinks 

• Some over-the-counter and prescribed medicines

• Illegal recreational drugs 

Symptoms of arrhythmia depend on what type of arrhythmia you have. You can learn more about some of the different types, in the content on this page. The most common symptoms include:

• Feeling dizzy

• Feeling like you might faint or “blackout”

• Having heart palpitations (a thumping or fluttering feeling in your chest) 

• Having chest discomfort

• Fatigue

If you have symptoms of arrhythmia or have a history of unexplained sudden death in your family, make sure to speak to your GP. They can refer you to a heart specialist (cardiologist) or an electrophysiologist who specialises in heart rhythm disorders. 

It’s important to note that although an arrhythmia can cause heart palpitations, the two have their differences. Whilst they share some of the same triggers, such as caffeine, alcohol, exercise and some medicines, for some people, heart palpitations can be short-term and may be managed with a few lifestyle changes. However, sometimes they can be a sign of an underlying heart condition, such as an arrhythmia. It’s advised to speak to your GP if you keep experiencing them and you’re concerned. 

Make sure to call 999 if you have palpitations and:

• You have shortness of breath

• You have chest pain

• You feel faint

• You feel dizzy

The treatment for arrhythmia depends on the type of arrhythmia you have. Underlying causes of arrhythmia also need to be treated. If you have an arrhythmia, you’ll be assessed by your doctor who will consider the most suitable treatment for you. Treatments can involve:

Medicines – to stop or prevent an arrhythmia. Medicines can also help control the rate of an arrhythmia

Catheter ablation – this is a keyhole treatment which is done under local or general anaesthetic. During this, the diseased tissue in your heart which is causing the arrhythmia is carefully destroyed

Electrical cardioversion – a treatment that uses electricity to shock the heart. This can help the heart regain its normal rhythm. Electrical cardioversion is normally done under anaesthetic or sedation

Pacemaker – this is a small device which has a battery. It’s implanted into your chest and produces electrical signals to help your heart beat at a normal rhythm and rate

Implantable cardioverter defibrillator (ICD) – this is like a pacemaker. It monitors your heart rhythm and shocks your heart back into a normal rhythm when needed

Treatment for an arrhythmia aims to control it or help prevent it from happening in the future. Preventing arrhythmias isn’t always possible, but there are lifestyle changes that can help reduce your risk of developing a heart condition. You can learn more about taking steps to look after your heart in our article that explores heart health. For face-to-face specialist assessment and advice, and if appropriate, diagnostics and treatment, from a private Cardiologist at Circle Health Group please find out more on how to book here1.

The most effective way to diagnose an arrhythmia is with an electrocardiogram (ECG). An ECG is often used alongside other tests to help diagnose and monitor conditions affecting the heart. Your GP or heart specialist (cardiologist) may request an ECG to check whether there is a problem with your heart. The ECG is carried out by a trained healthcare professional and can be done at a hospital, clinic or sometimes at your GP surgery.

What is an ECG?
An electrocardiogram (ECG) is a test that’s used to check your heart’s electrical activity and rhythm. Electrical signals from the heart are detected by sensors called electrodes every time it beats. The signals are recorded by a machine and then a doctor reviews the results. It’s important not to confuse with echocardiograms which are a scan of the heart.

An ECG can be used to investigate symptoms of heart problems like dizziness, shortness of breath, chest pain and palpitations. It can help to diagnose:

Arrythmias – when there is an abnormal heart rhythm

Coronary heart disease – when a build-up of fatty substances in the blood blocks or interrupts the heart’s blood supply

Heart attacks – when the heart’s blood supply is blocked

Cardiomyopathy – when the walls of the heart become thickened or enlarged

You don’t need to do anything different to prepare for an ECG. An ECG usually takes a few minutes and you should be able to go home afterwards. If you’re already staying in hospital, you should be able to return to your ward. Some people might be asked to wear a small portable ECG for up to 14 days. This will depend on the symptoms and the type of heart problem suspected. If you have symptoms which are triggered by exercise, you might be advised to wear an exercise ECG to check your heart rhythm while you’re using an exercise bike or a treadmill. It’s important to ask for a copy of your ECG so you can take it with you to appointments with your cardiologist or heart rhythm specialist.

Other tests can be used to diagnose arrhythmias like:

Echocardiograms (echo) – an ultrasound scan of your heart

Cardiac event recorder – a device which records symptoms over time when they happen

Electrophysiological (EP) study – a test which looks at problems with the electrical signals in your heart. This happens while you’re under sedation and a soft wire is passed up a vein in your leg into your heart.


Your guide to heart health

From our very first heartbeats, our hearts work hard to help us keep healthy. Kickstarting a healthier lifestyle is a great way to help take care of your heart health, no matter your age. Making small changes to the way you live your life can make a big impact. From the importance of heart health to the lifestyle choices you can make, take a look at our top tips for showing your heart a little love.



A normal heart rate is between 60-100 beats per minute while you’re at rest. The more physically fit you are, the lower your heart rate might be. For example, an athlete might have a resting heart rate lower than 60 beats per minute. Your lifestyle can affect your heart rate, if you’re overweight, you smoke or drink alcohol. If your heart rate is continuously lower than 60 beats per minute or above 120 beats per minute, speak to your GP this may be normal for you but it’s important to get it checked. 

If you know how to check it, your heart rate can be measured by checking your neck or wrist pulse. You might find using an activity tracker helpful to check your heart rate. At Boots, we have different types of trackers that can measure things like your step count and how well you’re sleeping. Activity trackers can help you monitor your health, but they can’t be used to diagnose a medical condition. It’s important to speak to your GP if you do notice any unusual patterns or have any symptoms.

Your blood pressure is the force of your blood on blood vessel walls while it’s moving through your body. Your heart rate is the number of times your heart beats per minute. Both help to make sure your brain and organs get enough blood. They function separately but they can change in response to each other. Your heart rate can have a direct effect on your blood pressure. For example, if you have atrial fibrillation (AF), your heart can feel like it’s pounding, fluttering or beating irregularly. The way the heart beats in atrial fibrillation reduces the heart's performance and efficiency, which can lead to low blood pressure (hypotension). 

Depending on the cause, you might find living with arrhythmia doesn’t have too much of an impact on your life. However, you may find it challenging, so it’s important to get support from your GP or family if you need it. If arrhythmia affects your driving, you need to speak to the Driver and Vehicle Licensing Agency (DVLA) and your insurance company. You should speak to your GP for advice if you’re not sure whether you need to do this.

If you work at a height or with machines that could be dangerous, you may need to stop this work at least until an arrhythmia gets diagnosed or you’re being treated for an underlying condition. You should speak to your GP or cardiologist for advice. If your workplace has an occupational health department, speak to them if your job has been affected by your arrhythmia. 

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Page last reviewed by Boots Pharmacy team on 10/01/2024

At Boots, we understand the importance of maintaining a healthy heart, which is why we offer a range of advice, services, and products to support your heart health journey. Our pharmacists are here to provide guidance and answer any questions you may have about arrhythmia. Whether you need information on managing symptoms or understanding the causes of arrhythmia, we're here to help.