Atrial fibrillation (AF) is a heart rhythm disorder in which the electrical activity of the upper chambers becomes fast and disorganized, so the atria quiver instead of contracting and the ventricles beat irregularly. It is the most common sustained arrhythmia in adults, and its frequency climbs steeply with age. Some people feel it clearly, as a fluttering or racing chest, breathlessness or sudden fatigue. Many feel nothing at all, and the rhythm is found during a routine check or by a wearable.
What it measures
Atrial fibrillation is a rhythm diagnosis, not a number on a lab report. It is read from a tracing: on an ECG (electrocardiography) the organized P wave before each beat disappears, replaced by a fine irregular baseline, and the intervals between beats become irregularly irregular. Untreated, the ventricular rate at rest is often fast, and it fluctuates from beat to beat rather than sitting at a steady level.
Episodes come and go, so a single office tracing misses a lot. Longer recordings close the gap: a Holter monitor over a day or two, an adhesive patch worn for weeks, an implanted loop recorder, or the single-lead recordings built into watches. Guidelines conventionally count an episode as clinical atrial fibrillation once it is documented for at least 30 seconds; shorter device-detected episodes are called subclinical and handled more cautiously. The clinical picture is set out in more detail under Atrial fibrillation.
Typical values
There is no reference range here. What is standardized is how episodes are classified by duration, because that shapes treatment.
| Pattern | Definition |
|---|---|
| Paroxysmal | Stops on its own or with treatment, usually within seven days |
| Persistent | Continues beyond seven days, or needs a shock or drug to stop |
| Long-standing persistent | Continuous over twelve months while rhythm control is still pursued |
| Permanent | Patient and clinician accept the rhythm and stop trying to restore it |
Stroke risk is scored separately, most often with CHA2DS2-VASc, which adds points for heart failure, high blood pressure, older age, diabetes, prior stroke, vascular disease and sex. The annual risk attached to each score differs between the cohorts it has been measured in, so published percentages are approximate.
Why it matters for longevity
Blood pools in the left atrial appendage when the atria stop contracting properly, clots can form there, and a fragment that breaks loose travels to the brain. Atrial fibrillation is associated with several times the background risk of Stroke, and those strokes tend to be larger and more disabling than average. In randomized trials, oral anticoagulation substantially reduced that risk; aspirin does not do the same job.
The rhythm also costs the heart output over time, and it is associated with heart failure, reduced exercise capacity and repeated admissions. Observational data link it with faster cognitive decline as well. It is a marker as much as a disease: it usually appears in a heart already shaped by years of high blood pressure, excess weight or alcohol.
What changes it
Age, sex, genetics and prior heart disease are fixed. Much of the rest is not.
- Blood pressure. Long-standing hypertension stretches the left atrium and is one of the strongest modifiable drivers.
- Weight. Excess weight raises risk, and structured weight-loss programs reduced symptom burden and time spent in the rhythm.
- Alcohol. Intake tracks with risk dose-dependently, and a randomized trial of abstinence in regular drinkers lowered recurrence.
- Sleep apnea. Untreated obstructive sleep apnea is associated with more atrial fibrillation and more recurrence, so screening is worthwhile if you snore heavily.
- Thyroid function. An overactive thyroid can provoke the rhythm and is checked at diagnosis.
- Treatment. Rate control, rhythm-control drugs, cardioversion and catheter ablation each have a place; ablation reduced recurrence and improved symptoms more than drugs in trials.
Related reading
- Heart Health: A Prevention Guide for Longevity
- Coffee and Longevity: What the Research Shows
- Sauna and Heart Health: What the Research Shows
- Stroke
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.