Part C
Atrial fibrillation: an irregular rhythm, explained
Atrial fibrillation is the most common treated heart rhythm problem, and many people have no symptoms. Here is what it is, why it matters and how it is managed.
Overview
Your heart is meant to beat in a steady, organised pattern. When someone is told they have atrial fibrillation, often shortened to AF or AFib, that pattern has become irregular, and the diagnosis can feel alarming because the word "fibrillation" sounds severe. This page explains what AF is, what it can feel like, what raises the chance of it, how it is detected and what treatment aims to do. It also sets out why the stroke connection is the main reason AF is taken seriously.
What atrial fibrillation is
The US Centers for Disease Control and Prevention (CDC) describes AF as the most common type of treated heart arrhythmia, which is a heartbeat that is too slow, too fast or irregular. In AF, the normal beating of the two upper chambers (the atria) becomes irregular, and blood does not flow as well as it should from the atria to the two lower chambers (the ventricles). The NHS puts the cause in simple terms: a fault in the heart's electrical system. If you want the basic layout first, how the heart works covers the four chambers.
AF does not behave the same way in everyone. The NHS describes episodes that stop on their own, episodes that continue until they are treated, and AF that is present all the time. The heartbeat may also be fast, and the NHS lists a heart rate above 100 beats per minute among the signs.
Symptoms, and the possibility of none
Many people notice the rhythm directly as palpitations, which the NHS describes as a pounding, racing, fluttering or skipped-beat feeling that can last seconds to minutes. Other reported symptoms include tiredness, breathlessness, light-headedness or dizziness, and chest pain or tightness. The NHS adds that some people have no symptoms at all and only learn they have AF during a routine check or another test, and the CDC says the same.
That last point matters. A quiet rhythm problem can still carry a stroke risk, so the absence of symptoms is not proof that nothing is wrong. It is also why a pulse check is worth taking seriously when a clinician suggests one.
Causes and risk factors
AF has no single cause. The CDC says the risk rises with age and that high blood pressure accounts for about 1 in 5 cases. Its list of risk factors also includes obesity, diabetes, heart failure, ischemic heart disease (reduced blood supply to the heart), an overactive thyroid (hyperthyroidism), chronic kidney disease, moderate to heavy alcohol use and smoking. The NHS adds sleep apnoea, mitral valve problems and a previous heart attack to its list, and notes that some medicines and long-distance endurance sport have been linked with AF.
Several of these are things a person can influence. High blood pressure is the one with the clearest numbers behind it, and conditions such as heart failure and heart valve problems can sit alongside AF. Services and risk patterns differ between countries, so this list describes what the named sources report rather than a prediction for any one reader.
How AF is detected
The first clue is often an irregular pulse, felt by a clinician or noticed by the person. The NHS says a suspected case is referred to a specialist who reviews symptoms, checks the heart rate and may order an electrocardiogram (ECG), an echocardiogram (an ultrasound scan of the heart), a chest X-ray and blood tests. These tests check the rhythm and help rule out other causes of the symptoms. Because episodes can stop on their own, as described above, a clinician will usually ask when symptoms happen and how long they last.
What treatment aims to do
The NHS describes there being no cure for AF at present, with treatment aimed at managing symptoms and reducing complications. In outline, there are three jobs. The first is controlling the heart rate and rhythm, for which the NHS names beta blockers as one type of medicine, alongside procedures such as cardioversion (an electrical reset of the rhythm) or ablation. The second is lowering the risk of blood clots and stroke, where the NHS names anticoagulants, medicines that stop clots forming. The third is treating any underlying condition or medicine that is contributing.
The US National Heart, Lung, and Blood Institute (NHLBI) explains the reasoning: blood may pool in the heart, which raises the chance of clots forming and can lead to stroke. The CDC states that AF increases a person's risk for stroke and that blood-thinning medicine is part of treatment for that reason. How a clot formed in the heart can reach the brain is explained in atrial fibrillation, stroke and the heart-brain link, and the warning signs are set out in stroke signs and what to do. Choosing, starting or stopping any medicine is a decision for a clinician who knows the individual.
When to see a clinician
See a doctor if you have palpitations that keep happening or are getting worse, or if you already have a diagnosis and your treatment does not seem to be helping. Emergency numbers differ by country, so use your local one. The NHS advises calling the emergency number (999 in the United Kingdom) if a fast or irregular heartbeat comes with chest pain, shortness of breath, fainting, one-sided weakness or numbness, confusion or difficulty speaking, and advises against driving yourself to hospital.
In short
Atrial fibrillation is an irregular, often fast rhythm that begins in the upper chambers of the heart. It can cause palpitations, breathlessness and tiredness, or nothing noticeable at all. It is found by checking the pulse and recording an ECG, and treatment focuses on rate and rhythm control plus anticoagulant medicines to lower stroke risk.