Atrial fibrillation
The commonest abnormal heart rhythm, in which the upper chambers of the heart beat in a fast, disorganised way, making the pulse irregular. It may cause palpitations, breathlessness or tiredness, or none at all — and its main danger is a raised risk of stroke, which treatment can greatly reduce.
What it is
Atrial fibrillation (AF) is the most common sustained abnormal heart rhythm. Normally the heart's upper chambers (atria) beat in a coordinated way, driven by a regular electrical signal. In AF, chaotic electrical activity makes the atria quiver rather than contract properly, and the resulting heartbeat becomes fast and irregular. It becomes more common with age and is often linked to high blood pressure, heart valve or coronary disease, heart failure, an overactive thyroid, obesity, sleep apnoea and alcohol. Some people feel it clearly — palpitations, a fluttering or racing heart, breathlessness, reduced exercise tolerance, tiredness or dizziness — while others have no symptoms and it is found by chance. Its most important consequence is the risk of stroke: because blood does not flow smoothly through the fibrillating atria, clots can form and travel to the brain. AF can be occasional (paroxysmal) or persistent. It is diagnosed on an ECG, and blood tests help look for treatable drivers such as an overactive thyroid and check electrolytes. Management has two aims: controlling the rhythm or rate to relieve symptoms, and, crucially, assessing stroke risk to decide on blood-thinning treatment, which markedly reduces that risk.
Key lab markers
- Thyroid function (TSH, free T4) — an overactive thyroid is an important, treatable trigger of AF and is checked routinely.
- Potassium and magnesium — electrolyte disturbances can provoke or worsen the rhythm.
- Kidney function — needed to choose and dose blood-thinning and rhythm medications safely.
- Full blood count — anaemia can worsen symptoms; also relevant before anticoagulation.
- An ECG — the actual diagnosis; blood tests support it and look for causes.
Symptoms
- Palpitations — a fluttering, racing or thumping, irregular heartbeat
- Breathlessness, especially on exertion
- Fatigue and reduced exercise tolerance
- Dizziness or light-headedness
- Chest discomfort
- Sometimes no symptoms — found by chance or when a complication occurs
Related symptoms
Related lab panels
When to discuss with a doctor
An irregular pulse, palpitations, unexplained breathlessness or tiredness, or dizziness should be assessed by a doctor, who can confirm atrial fibrillation on an ECG and check the thyroid and electrolytes for treatable drivers. The key reason to diagnose and treat AF, even when symptoms are mild, is to assess and reduce stroke risk — for many people this means blood-thinning treatment, a decision made with your doctor. Seek urgent care for palpitations with chest pain, severe breathlessness or fainting, or for any symptoms suggesting a stroke (sudden facial droop, arm weakness or speech difficulty), which is an emergency. Mediora.AI can surface a thyroid or electrolyte pattern that may be driving the rhythm, but atrial fibrillation is diagnosed on an ECG and its management, especially the stroke-prevention decision, belongs with your doctor.