Atrial Arrhythmia
Atrial Fibrillation
Atrial fibrillation is a heart rhythm disorder in which the electrical activity of the upper chambers of the heart, the atria, becomes disorganised. It can cause an irregular heartbeat and may affect how the chambers of the heart work together.
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Understanding AF
What Is Atrial Fibrillation?
In a normal rhythm, electrical signals begin in the sinus node and spread through the atria in an organised sequence, so the atria contract in a coordinated way.
In atrial fibrillation, electrical activation in the atria becomes disorganised and irregular, and coordinated atrial contraction is lost.
Only some of these irregular signals are conducted through the AV node to the ventricles. This can produce an irregular, and sometimes rapid, ventricular response, which is often felt as an irregular pulse or palpitations.
AF can be present continuously or come and go, and some people have few or no symptoms.
Normal atrial activation compared with AF activation
A scientific comparison
Normal Sinus Rhythm and Atrial Fibrillation
How electrical activation is organised in each rhythm.
Reference rhythm
Normal Sinus Rhythm
- Organised electrical activation, starting in the sinus node
- Coordinated atrial activity
- Regular rhythm
Rhythm disorder
Atrial Fibrillation
- Disorganised atrial activation
- Loss of coordinated atrial electrical activity
- Irregular ventricular response
Mechanisms
How AF Can Develop
The left atrium and the pulmonary veins, which carry blood from the lungs into the left atrium, are important in many people with AF. How AF starts and continues differs between patients and can change over time.
Left atrium and pulmonary veins
Left atrium
The upper left chamber, where much of the electrical activity relevant to AF is found.
Pulmonary veins
In some patients, rapid electrical activity in or near these veins can act as a trigger.
Initiation
A trigger may start AF when the surrounding atrial tissue is able to sustain it.
Maintenance
Changes in atrial tissue and its electrical properties may help AF continue once it has started.
Classification
Types of AF
AF is commonly described by how long episodes last and whether they stop on their own. The type can change over time and is part of the clinical assessment.
Self-terminating
Paroxysmal AF
Episodes start and stop on their own, usually within 7 days.
Sustained
Persistent AF
AF that lasts longer than 7 days, or that needs treatment to restore normal rhythm.
Continuous
Long-standing Persistent AF
Continuous AF lasting longer than 12 months.
These are commonly used clinical definitions. How they apply to an individual is a matter of clinical assessment.
What patients may notice
Symptoms of AF
Symptoms vary. Some people notice them clearly, while others have few symptoms or none.
Palpitations
Awareness of the heartbeat, which may feel fluttering or pounding.
Rapid or irregular heartbeat
A heartbeat that feels fast, uneven or unpredictable.
Fatigue
Tiredness that is out of proportion to activity.
Shortness of breath
Feeling breathless at rest or with activity.
Dizziness
Feeling light-headed or unsteady.
Reduced exercise tolerance
Tiring more quickly than usual during activity.
Chest discomfort
Pressure or discomfort in the chest that needs medical assessment.
Fainting, chest pain or severe breathlessness need urgent medical care.
Associated factors
Risk Factors
Several factors are associated with a higher likelihood of AF. Having one or more of them does not mean a person will develop AF, and many people with AF have none of them.
- Increasing age
- High blood pressure (hypertension)
- Structural heart disease
- Sleep apnoea
- Obesity
- Thyroid disorders
- Diabetes
- Alcohol
- Family or genetic factors
Assessment
How AF Is Diagnosed
Diagnosis relies on recording the heart rhythm. Which tests are used depends on the symptoms and on how often the rhythm problem occurs.
A recording of the heart’s electrical activity that can show AF when it is present at the time of the test.
Continuous ECG recording over a period of time, which can help detect episodes that come and go.
A device used when symptoms are occasional, activated around the time symptoms occur.
Longer-term rhythm monitoring
Extended monitoring may be considered when episodes are infrequent or when a rhythm problem is suspected but has not yet been recorded.
Echocardiography
An ultrasound examination that may be used, where clinically indicated, to assess the structure and function of the heart.
Further assessment of the heart’s electrical system when relevant, for example when catheter ablation is being considered.
ECG
What Atrial Fibrillation Can Look Like on an ECG
- An irregular rhythm, with varying intervals between heartbeats
- No clear, organised P waves before the QRS complexes
- A variable ventricular response, which may be slow, normal or fast
An ECG is interpreted by a clinician together with symptoms and other findings.
Stroke prevention
AF and Stroke Risk
Left atrium and left atrial appendage
During AF the atria do not contract effectively, and blood may move more slowly in parts of the atrium, particularly in the left atrial appendage, a small pouch of the left atrium.
In some patients this may allow a blood clot (thrombus) to form. If a clot travels to the brain, it can cause a stroke.
Stroke risk differs between patients and depends on several individual factors. Whether anticoagulation (blood-thinning treatment) is recommended is an individual decision, made after clinical assessment and discussed with the patient.
Treatment approach
Treatment Approach
Treatment is individualised. It may combine more than one element, and the balance depends on symptoms, the type of AF, other conditions and patient preference. Not every patient follows the same pathway.
Rate Control
Treatment that aims to keep the heart rate controlled during AF.
Rhythm Control
Approaches that aim to restore and maintain normal rhythm, such as medication or electrical cardioversion.
Anticoagulation Assessment
Assessment of stroke risk and discussion of whether blood-thinning treatment is appropriate.
Catheter Ablation
A catheter-based procedure that may be considered in selected patients, where clinically appropriate.
Catheter-based treatment
Atrial Fibrillation Ablation
Left atrium, pulmonary veins and catheter
AF ablation is a catheter-based treatment. Thin catheters are guided through blood vessels to the heart, where they are used to treat areas of the atria involved in AF.
A key part of many AF ablation procedures is pulmonary vein isolation: creating lesions around the pulmonary veins so that electrical signals from these regions can no longer reach the rest of the left atrium.
Whether ablation is appropriate depends on clinical assessment, including the type of AF, symptoms, previous treatment and individual circumstances.
Energy sources
Radiofrequency, Cryoablation and Pulsed Field Ablation
Different energy sources can be used to create the lesions needed during ablation. They differ in how they act on tissue, and the choice depends on clinical factors and the procedure planned.
Thermal energy
Radiofrequency Ablation
Uses heat to create small lesions in targeted tissue.
Controlled freezing
Cryoablation
Uses controlled freezing to create lesions in targeted tissue.
Pulsed electrical field
Pulsed Field Ablation
Uses pulsed electrical field technology to create lesions in targeted tissue.
Mapping
3D Electroanatomical Mapping
3D mapping systems can be used during ablation to support:
- Reconstructing the anatomy of the heart chamber
- Locating catheters in three-dimensional space
- Mapping electrical activity
- Planning and guiding treatment
3D electroanatomical map of the left atrium
Preparation
Before the Procedure
Preparation is planned for each patient. The stages below are general and may differ between patients.
Clinical assessment
Review of symptoms, rhythm recordings and medical history.
Medication review
Current medicines, including any anticoagulant treatment, are reviewed and any changes are discussed.
Tests or imaging if required
Additional tests or imaging may be requested, depending on the individual case.
Procedure instructions
Practical instructions for the day of the procedure are explained in advance.
Fasting instructions where applicable
If fasting is needed, the instructions are given beforehand.
The day of treatment
Procedure Day
These are the general stages of a catheter ablation procedure. Specific details are explained by the care team.
Admission
Arrival and a final review of the plan with the care team.
Preparation
Monitoring is set up and the planned form of sedation or anaesthesia is given.
Catheter access
Thin catheters are introduced through blood vessels, usually in the groin.
Mapping
Catheters record electrical activity, and a 3D map of the heart chamber may be created.
Ablation
Energy is delivered to the targeted areas according to the planned strategy.
Reassessment
Electrical activity is checked again to assess the effect of treatment.
Recovery
Monitoring continues while the patient recovers.
Recovery and follow-up
After the Procedure
Monitoring and recovery
Heart rhythm and general condition are monitored. Recovery depends on the individual patient, and guidance on activity is given by the care team.
Medication review
Medicines, including any anticoagulant treatment, are reviewed and the plan is explained.
Follow-up
Follow-up appointments are arranged to review symptoms and progress.
Rhythm monitoring
Rhythm monitoring may be used after ablation where appropriate.
Educational comparison
Before and After Detailed Mapping
A technical comparison of two stages of the same process. It is not a patient result.
Before Detailed Mapping
- Arrhythmia identified
- Source not yet fully localised
After Detailed Mapping
- Electrical anatomy mapped
- Target region identified
- Treatment strategy refined
Educational illustration of a general process. It does not represent an individual patient and does not imply any treatment result.
Questions
Frequently Asked Questions
Is AF always symptomatic?
No. Some people notice symptoms clearly, while others have few symptoms or none, and AF is found during a routine check or ECG.
Can AF come and go?
Yes. In paroxysmal AF, episodes start and stop on their own. In some patients AF becomes more sustained over time.
How is AF diagnosed?
By recording the heart rhythm, usually with an ECG. If episodes are occasional, longer monitoring such as Holter monitoring or an event recorder may be used.
Why can AF increase stroke risk?
In AF, blood may move more slowly in parts of the atrium, which in some patients may allow clots to form. Risk varies between patients and treatment decisions are individualised.
When is catheter ablation considered?
In selected patients, after clinical assessment, depending on symptoms, the type of AF, previous treatment and individual circumstances.
What is pulmonary vein isolation?
A technique in which lesions are created around the pulmonary veins to electrically isolate them from the rest of the left atrium.
What is PFA?
Pulsed field ablation is an ablation approach that uses pulsed electrical fields to create lesions in targeted tissue.
Is follow-up needed after ablation?
Yes. Follow-up is arranged to review symptoms, rhythm and medicines, and the schedule depends on the individual patient.
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