Evidence checked as of October 2026. Written by The Wellness Team.
What is atrial fibrillation?
Atrial fibrillation, or AF, is an irregular and often fast heart rhythm that starts in the upper chambers of the heart. It can come and go, which doctors call paroxysmal AF, or it can be constant. Some people feel it clearly. Others have no symptoms and only find out from a routine pulse check or a screening test.
The reason it matters is not the palpitations. AF allows blood to pool in the heart, which raises the chance of a clot and a stroke. Finding it and treating the stroke risk is the main goal of care.
What symptoms should make you think of AF?
NICE guideline NG196 lists breathlessness, palpitations, fainting or dizziness, chest discomfort, and stroke or transient ischaemic attack as reasons to check the pulse for an irregular rhythm. Many people describe a fluttering, thumping or racing heartbeat, or feeling tired and short of breath for no clear reason.
Call 999 for chest pain, collapse, severe breathlessness, or face drooping, arm weakness or slurred speech. A stroke needs emergency treatment immediately.
How is AF diagnosed?
NICE advises manual pulse palpation first when AF is suspected. If the pulse is irregular, with or without symptoms, a 12-lead ECG is used to make the diagnosis. An ECG takes a few minutes and records the heart's electrical activity.
AF that comes and goes can be missed on a short tracing. For suspected paroxysmal AF that a standard ECG does not detect, NICE recommends a 24-hour ambulatory ECG if episodes happen at least daily, and a longer monitor or event recorder if they are less frequent. Smartwatch alerts can prompt a check, but a diagnosis of AF still depends on a medical-grade ECG recording reviewed by a clinician.
Blood tests for thyroid function, kidney function and blood count, and sometimes an echocardiogram, help look for causes and for structural heart disease.
What is the CHA2DS2-VASc score?
Once AF is confirmed, NICE recommends assessing stroke risk with the CHA2DS2-VASc score. It counts factors including heart failure, high blood pressure, age, diabetes, previous stroke or TIA, vascular disease and sex. NICE also recommends using the ORBIT tool to assess bleeding risk, and discussing both results with the person before agreeing treatment.
For many people the score points towards an anticoagulant to reduce stroke risk. That is a shared decision, because the benefit is lower stroke risk and the cost is a higher chance of bleeding. The decision also depends on kidney and liver function, other medicines and alcohol intake.
What else can reduce AF episodes?
Rate or rhythm control with medicines, cardioversion or ablation may be used to control symptoms, and a cardiologist guides that choice. Everyday factors matter too. Alcohol is a well-recognised trigger. Sleep apnoea, high blood pressure, obesity, thyroid disease and heavy caffeine intake can all contribute, and treating them can reduce episodes.
How can The Online GP help?
A doctor can take a careful history, check your pulse, arrange an ECG and bloods where indicated, and decide whether longer rhythm monitoring or cardiology review is appropriate. As of October 2026, a telephone consultation with The Online GP is £59 and a video consultation is £150. Tests and onward care are separate costs, and the total is confirmed before booking.
For related reading, see our guide to heart palpitations and ECG: https://www.theonlinegp.com/blog/heart-palpitations-london-ecg-when-urgent
Call +44 20 3951 3429, message on WhatsApp on 07961 280835 or email team@thewellnesslondon.com. This service does not replace emergency care.
Evidence and limits
NICE guideline NG196, atrial fibrillation: diagnosis and management. https://www.nice.org.uk/guidance/ng196/chapter/Recommendations
NHS: atrial fibrillation. https://www.nhs.uk/conditions/atrial-fibrillation/
This is general information, not personal medical advice. Chest pain, fainting or stroke symptoms need an ambulance.