Atrial Fibrillation Explained: When the Heart Falls Out of Rhythm

Atrial Fibrillation: Symptoms, Stroke Risk and Treatment

Most of us imagine a healthy heartbeat as a perfectly steady tick-tock.

In reality, the heart is not a metronome. It speeds up when you climb stairs, slows during sleep and responds to stress, illness, medicines and exercise.

Atrial fibrillation is different. Often shortened to AF or AFib, it occurs when the electrical signals in the heart's upper chambers become disorganised. The pulse may feel fast, uneven or as though beats are being missed.

Some people describe a flutter, thump or drum roll in the chest. Others feel tired or breathless. Many notice nothing at all.

That last point is important. Atrial fibrillation may be silent, but it can still increase the risk of stroke and other complications. Understanding it is especially relevant in midlife and later life because the likelihood of developing AF rises with age.

What Is Atrial Fibrillation?

The heart has four chambers. The two upper chambers are called the atria, and the two lower chambers are the ventricles.

Normally, each heartbeat begins with an organised electrical signal from the heart's natural pacemaker. The signal moves across the atria and then through the ventricles, allowing the chambers to squeeze in a coordinated sequence.

During atrial fibrillation, many competing electrical signals fire through the atria. Instead of making one strong, organised contraction, the atria quiver or twitch rapidly. The ventricles then receive an uneven stream of signals, which produces an irregular pulse.

The pulse is often faster than usual, although it can sometimes be within a usual range or even slow, particularly when medicines are being used to control it.

The Heart Foundation's overview of atrial fibrillation explains how this disrupted electrical activity affects the heart's pumping rhythm.

AF is not usually immediately life-threatening, but a new or unexplained irregular rhythm still warrants medical assessment. The condition can affect quality of life and contribute to serious complications, particularly stroke and heart failure.

What Does Atrial Fibrillation Feel Like?

Atrial fibrillation does not feel the same for everyone.

Possible symptoms include:

• A racing, pounding, fluttering or irregular heartbeat

• The sensation that the heart is skipping or missing beats

• Shortness of breath

• Unusual tiredness or weakness

• Dizziness, light-headedness or feeling faint

• Reduced ability to exercise or complete normal activities

• Chest pain, pressure or discomfort

Symptoms may last for minutes or hours, appear on and off, or continue for much longer. Some people first discover AF during a routine health check or a test performed for another reason.

These symptoms are not specific to atrial fibrillation. Anxiety, thyroid conditions, anaemia, dehydration, infections, other rhythm disorders and several additional conditions may cause similar sensations. An electrocardiogram is normally needed to confirm what the heart is doing.

Is an Irregular Heartbeat Always Atrial Fibrillation?

No.

Occasional extra or missed beats are common and may not indicate AF. Other rhythm conditions can also cause palpitations, a fast heartbeat or an uneven pulse.

Atrial flutter, for example, also begins in the atria. Its electrical activity is generally more organised than the chaotic activity seen in AF, although both conditions can cause similar symptoms and both require appropriate medical assessment.

You cannot reliably identify the rhythm from the sensation alone. If palpitations keep returning, become more noticeable or are accompanied by other symptoms, arrange a medical assessment rather than trying to diagnose the cause yourself.

Why Does Atrial Fibrillation Become More Common With Age?

AF can affect younger adults, but its likelihood increases as people get older. Ageing can bring changes to the heart's structure and electrical pathways, while health conditions associated with AF also become more common over time.

Factors that may increase the likelihood of AF include:

• High blood pressure

• Coronary heart disease or a previous heart attack

• Heart failure

• Heart valve disease

• Diabetes

• Overweight or obesity

• Obstructive sleep apnoea

• An overactive thyroid

• Chronic kidney or lung disease

• Smoking

• Higher alcohol intake, particularly binge drinking

• A family history of atrial fibrillation

• Some heart or chest surgery

High blood pressure is one of the most important modifiable factors. AtheroCare's guide to what blood pressure means and why it matters explains the two numbers and how ongoing high pressure can strain the cardiovascular system.

Family history may also influence risk, although it does not mean that AF is inevitable. Read more about what a family history of heart disease may mean for you.

What Are the Different Patterns of Atrial Fibrillation?

Healthcare professionals may describe AF according to how long it lasts and how it is being managed. The current ACC/AHA clinical guideline summary also places these patterns within a wider progression of AF risk and care.

Paroxysmal atrial fibrillation

Episodes begin and end on their own. They may last for minutes, hours or several days, but stop within seven days.

Persistent atrial fibrillation

The abnormal rhythm continues for more than seven days and may require medicine or a procedure to restore a normal rhythm.

Long-standing persistent atrial fibrillation

AF has continued for more than 12 months, although rhythm-control treatment may still be considered.

Permanent atrial fibrillation

The patient and healthcare team have decided not to make further attempts to restore or maintain a normal rhythm. Treatment instead focuses on controlling the heart rate, reducing stroke risk and managing symptoms and related conditions.

The word “permanent” describes the management approach. It does not mean that medical care has stopped or that nothing can be done.

Some people remain in one pattern for years. In others, episodes become more frequent or last longer over time. Regular reassessment matters because symptoms, stroke risk and treatment needs can change.

What Can Trigger an AF Episode?

A cause and a trigger are not always the same thing.

An underlying condition such as high blood pressure or sleep apnoea may make AF more likely to develop. A trigger is something that appears to set off an episode in a person who is already susceptible.

Reported triggers include:

• Alcohol

• Dehydration

• Infection or fever

• Poor sleep or unusual fatigue

• Emotional stress

• Smoking

• Some medicines, decongestants or stimulants

• Intense exercise

• Caffeine in some individuals

Triggers are highly personal. Coffee may bother one person and have no noticeable effect on another. Rather than eliminating everything at once, it can be useful to keep a simple record of your symptoms, sleep, drinks, illness, activity and medicines, then discuss any pattern with a healthcare professional.

Do not stop a prescribed medicine because you suspect it is a trigger without first speaking with the person who prescribed it.

Why Can Atrial Fibrillation Increase Stroke Risk?

This is the complication that often matters most.

When the atria do not contract effectively, blood can move more slowly and pool inside part of the heart. A clot may form. If a piece of that clot travels through the bloodstream and blocks an artery in the brain, it can cause an ischaemic stroke.

AF can substantially increase stroke risk, but the level of risk is not the same for everyone. A healthcare professional will consider factors such as age, high blood pressure, diabetes, heart failure, blood vessel disease and any previous stroke or transient ischaemic attack.

People at sufficient risk may be prescribed an anticoagulant, sometimes informally called a blood thinner. These medicines reduce the blood's ability to form harmful clots. They do not remove AF, but they can greatly reduce the likelihood of an AF-related stroke.

Anticoagulants can also increase bleeding risk, so the decision requires an individual assessment. Take them exactly as directed. Do not skip doses, change the amount or stop treatment because your heartbeat feels normal without speaking with a qualified healthcare professional.

The 2024 European Society of Cardiology guidelines place stroke prevention alongside treatment of related conditions, symptom control and ongoing reassessment.

Can Atrial Fibrillation Affect the Heart in Other Ways?

Yes.

If the heart beats too quickly for long periods, it may not have enough time to fill properly between beats. The continuing strain can weaken the heart muscle in some people and may contribute to heart failure.

AF and heart failure can also make each other more difficult to manage. This is one reason persistent breathlessness, swelling, rapid weight changes or a marked reduction in exercise capacity should be discussed with a healthcare professional.

Even without a major complication, frequent symptoms can affect sleep, confidence, travel, exercise and day-to-day independence. Effective treatment is not only about a number on a monitor. It should also help a person function and feel better.

How Is Atrial Fibrillation Diagnosed?

A healthcare professional will ask about your symptoms, medical history, family history, medicines, alcohol intake and possible triggers. They may check your pulse and listen to your heart.

The main test used to confirm AF is an electrocardiogram, usually called an ECG. It records the heart's electrical activity and can show the characteristic irregular rhythm.

Because AF may come and go, a brief ECG can look normal between episodes. Longer monitoring may therefore be needed, using devices such as:

• A Holter monitor worn for a day or longer

• An event monitor used over several weeks

• A patch monitor

• An implantable loop recorder for longer-term monitoring in selected cases

Other investigations may include:

• Blood tests to look for thyroid problems, anaemia, electrolyte changes and kidney or liver issues

• An echocardiogram to examine the heart's chambers, valves and pumping function

• Additional tests based on symptoms and medical history

The National Heart, Lung, and Blood Institute's diagnosis guide provides an overview of the assessment and tests that may be used.

Can a Smartwatch Diagnose Atrial Fibrillation?

A smartwatch or portable rhythm device can be useful, particularly when symptoms are brief and have stopped before an appointment.

An irregular-rhythm alert or a saved single-lead ECG may give a healthcare professional helpful information. However, a consumer device should be treated as a clue rather than a complete diagnosis. False alerts and missed episodes can occur, and the recording needs to be interpreted in context.

If a device alerts you to a possible abnormal rhythm:

• Save the recording or screenshot if possible

• Note what you were doing and how you felt

• Record how long the episode appeared to last

• Share the information with a healthcare professional

Do not begin, stop or alter heart or anticoagulant medicine based only on a watch notification. The American Heart Association's AF diagnosis overview explains how device information may contribute to a wider medical assessment.

How Is Atrial Fibrillation Treated?

There is no single treatment plan that suits everyone.

Management depends on symptoms, how long AF has been present, other health conditions, stroke and bleeding risk, heart function and the person's preferences.

A treatment plan may address four broad goals.

1. Reduce the risk of stroke

An anticoagulant may be recommended after an individual assessment. In selected people who cannot use long-term anticoagulation, a specialist may discuss other options.

2. Control the heart rate

Rate-control medicines slow the response of the ventricles. The rhythm may remain irregular, but the heart is not beating as quickly and symptoms may improve.

3. Restore or maintain a regular rhythm

Rhythm-control treatment may include:

• Antiarrhythmic medicine

• Electrical cardioversion, which uses a controlled electrical shock under sedation or anaesthesia

• Pharmacological cardioversion using medicine

• Catheter ablation, which targets small areas of heart tissue involved in the abnormal electrical signals

A pacemaker may be useful in particular situations, but it is not a routine cure for AF. It may be considered when the heartbeat is too slow, when medicines create a slow rate or as part of another rhythm-control strategy.

4. Manage related conditions and risk factors

Treatment may also include managing blood pressure, diabetes, heart failure, weight, sleep apnoea, alcohol intake, smoking and other factors that can influence AF.

Current guidelines emphasise shared decision-making and regular review. A plan that was suitable at diagnosis may need to change as symptoms, health conditions or risk factors change.

Can You Exercise With Atrial Fibrillation?

Many people with well-managed AF can remain active, and regular moderate activity can support cardiovascular health, mobility, mood and healthy ageing.

The right type and intensity depend on your symptoms, fitness, medicines and other medical conditions. Avoid pushing through chest discomfort, faintness, severe breathlessness or a sustained racing heartbeat.

People who are newly diagnosed, have troublesome symptoms or have not exercised for some time should ask a healthcare professional what is appropriate before making a major change. AtheroCare's article on the connection between exercise and heart health offers a broader introduction to regular movement.

What Everyday Habits May Help?

Lifestyle measures do not replace prescribed treatment, but they can form an important part of AF care.

Depending on your circumstances, helpful steps may include:

• Taking medicines consistently

• Attending follow-up appointments

• Managing blood pressure and blood sugar

• Seeking assessment for possible sleep apnoea

• Working towards a healthy, sustainable weight where appropriate

• Limiting alcohol or avoiding it if it triggers episodes

• Not smoking

• Staying hydrated, particularly during illness or warm weather

• Choosing activity suited to your health and ability

• Maintaining a regular sleep routine

Poor sleep may affect several factors connected with heart health. Learn more about how sleep quality influences cardiovascular wellness.

When Should You Arrange a Medical Assessment?

Arrange a medical assessment if you notice:

• Palpitations that keep returning, last longer or are becoming more noticeable

• A pulse that repeatedly feels irregular

• New or unexplained breathlessness

• Unusual tiredness or a reduction in exercise tolerance

• Recurrent dizziness or light-headedness

• A smartwatch or rhythm device repeatedly reporting a possible irregular rhythm

If you have already been diagnosed with AF, seek advice if your symptoms change, treatment no longer seems effective or you are experiencing medicine side effects.

When Should You Seek Emergency Medical Help?

Contact the emergency medical service for your location immediately if a fast or irregular heartbeat occurs with:

• Chest pain, pressure, tightness or severe discomfort

• Severe or rapidly worsening shortness of breath

• Fainting, collapse or unresponsiveness

• Sudden weakness or numbness, particularly on one side of the body

• Facial drooping

• Sudden difficulty speaking, understanding speech or finding words

• Sudden loss of vision or marked visual disturbance

• A sudden severe headache, loss of balance or confusion

These may indicate a heart attack, stroke or another serious problem. Do not wait to see whether the symptoms settle, and do not drive yourself when emergency transport is available. Stroke-like symptoms that disappear after a few minutes can still be a transient ischaemic attack and require emergency assessment.

The CDC guide to stroke warning signs provides a clear overview of symptoms that require immediate action.

Questions to Ask Your Healthcare Professional

You may wish to ask:

• Has atrial fibrillation been confirmed on an ECG?

• What pattern of AF do I have?

• What may be contributing to it?

• What is my individual stroke risk?

• Would an anticoagulant benefit me, and what bleeding precautions matter?

• Is the goal to control my rate, restore my rhythm or both?

• What should I do when an episode begins?

• Are any of my medicines or over-the-counter products affecting my heart rhythm?

• Is exercise safe for me, and are there activities I should modify?

• Should I be assessed for sleep apnoea or another underlying condition?

• Would a home monitor or wearable device be useful in my situation?

• Which symptoms require urgent or emergency care?

• How often should my treatment and stroke risk be reviewed?

AtheroCare's heart health checklist of questions to ask your doctor may help you prepare for an appointment.

The Bottom Line

Atrial fibrillation is a common heart rhythm condition in which the upper chambers receive chaotic electrical signals and stop contracting in a coordinated way.

It may cause a racing or irregular heartbeat, tiredness, breathlessness, dizziness or reduced exercise capacity. It may also cause no noticeable symptoms.

AF is often manageable, but it is not something to dismiss. Medical assessment matters because treatment can help control symptoms, support heart function and reduce the risk of stroke.

The most useful next step is not to guess what an irregular heartbeat means. It is to have the rhythm properly recorded, understand your personal risks and work with a qualified healthcare professional on a plan that can be reviewed over time.

Related AtheroCare Reading

What Is Blood Pressure and Why Does It Matter?

Understand systolic and diastolic pressure and why ongoing high blood pressure affects the heart and blood vessels.

Family History of Heart Disease: What It Means and How to Lower Your Risk

Learn how inherited factors and everyday habits can both influence cardiovascular risk.

How Sleep Quality Influences Heart Health

Explore the relationship between sleep, blood pressure, metabolism and cardiovascular wellness.

The Connection Between Exercise and Heart Health

Read about the wider cardiovascular benefits of regular movement and practical ways to stay active.

What to Ask Your Doctor: A Heart Health Checklist

Prepare questions about symptoms, risk factors, tests, medicines and follow-up care.

References

Heart Foundation: What Is Atrial Fibrillation?

National Heart, Lung, and Blood Institute: What Is Atrial Fibrillation?

National Heart, Lung, and Blood Institute: AF Symptoms

National Heart, Lung, and Blood Institute: AF Causes and Risk Factors

National Heart, Lung, and Blood Institute: AF Diagnosis

National Heart, Lung, and Blood Institute: AF Treatment

European Society of Cardiology: 2024 Guidelines for the Management of Atrial Fibrillation

American College of Cardiology: 2023 AF Guideline Key Perspectives

American Heart Association: Key Patient Messages from the 2023 AF Clinical Practice Guideline

American Heart Association: How Is AFib Diagnosed?

NHS: Atrial Fibrillation

CDC: Signs and Symptoms of Stroke

Medical Disclaimer

This article is provided for general information and education only. It is not intended to provide medical advice, diagnosis or treatment.

Always speak with a qualified healthcare professional about symptoms, medicines, test results and your personal cardiovascular risk. Do not begin, stop or change any treatment based only on information in this article.