Atrial fibrillation is the most common sustained heart rhythm disturbance, and a large share of people who have it do not know. Its significance is not the palpitations — it is that untreated AF multiplies stroke risk several times over.
What is actually happening
In a normal rhythm, the upper chambers of the heart contract in a coordinated way and push blood into the lower chambers. In atrial fibrillation, the electrical activity in the upper chambers becomes chaotic. They quiver rather than contract, and the pulse becomes irregular — classically described as irregularly irregular, with no discernible pattern.
The problem this creates is mechanical. Blood that is not moved efficiently out of the atria can pool, particularly in a small pouch called the left atrial appendage. Pooled blood can clot. A clot that leaves the heart travels, and the most consequential place for it to lodge is the brain.
Why detection is the hard part
Some people feel AF unmistakably — a fluttering or pounding in the chest, breathlessness, light-headedness, chest discomfort, or a marked drop in exercise tolerance. Others feel nothing at all, and their AF is found incidentally during an examination for something else.
AF also comes in patterns. It may be paroxysmal, starting and stopping on its own over hours or days, which means a normal ECG in clinic does not rule it out. Persistent and permanent forms are continuous. Paroxysmal AF carries stroke risk too, which surprises people who assume intermittent means minor.
What increases the risk
- Age — incidence rises steeply after 65
- High blood pressure, the single biggest modifiable contributor
- Obesity and obstructive sleep apnea, which frequently travel together
- Alcohol, with a clear dose relationship
- Existing heart disease, heart failure, or valve problems
- Thyroid overactivity
- Diabetes and chronic kidney disease
Several of these are modifiable, and addressing them reduces both the likelihood of AF and its burden in people who already have it. Weight loss and treating sleep apnea have particularly good evidence.
How it is managed
Treatment runs on two tracks that address different problems.
Stroke prevention is assessed using a scoring system based on age, sex and coexisting conditions. Where risk is above a threshold, anticoagulation is recommended. This is the part that saves lives, and it is independent of whether you feel symptoms. It is worth knowing that aspirin is not an adequate substitute for anticoagulation in AF — an older assumption that current guidelines have moved away from.
Rhythm and rate is the second track — either controlling how fast the heart responds, or working to restore a normal rhythm through medication or a procedure. Which approach suits depends on symptoms, duration, age and heart structure.
Wearables
Consumer watches now detect irregular rhythms and some record a single-lead ECG. They find real AF, and they also produce false positives. Treat an alert as a reason to seek assessment rather than a diagnosis — confirmation needs a proper ECG or monitor. But do not dismiss one either, particularly if it recurs.
When to seek care
Book an assessment for a persistently irregular pulse, new palpitations, unexplained breathlessness or reduced exercise tolerance, or repeated wearable alerts.
Go to an emergency department for chest pain, severe breathlessness, fainting, or any sign of stroke — face drooping, arm weakness, speech difficulty. In Canada, call 911. Stroke treatment is time-dependent in a way that very little else in medicine is.
