Atrial Fibrillation: Why an Irregular Pulse Raises Stroke Risk
Atrial fibrillation is the most common sustained abnormal heart rhythm, and it is one of the few conditions where a simple finger on the wrist can change the course of someone’s life. Untreated, it multiplies the risk of stroke several times over. Treated, most of that excess risk disappears.
What happens in the heart
Normally the heart’s upper chambers, the atria, contract in a coordinated beat triggered by the sinus node. In atrial fibrillation the atrial muscle receives chaotic electrical signals from many sites at once, so instead of contracting it quivers. The ventricles then beat irregularly and often fast, because they respond to whichever signals get through.
Two consequences follow. The heart pumps less efficiently, typically losing 15 to 20 percent of its output, which causes breathlessness and fatigue. More importantly, blood pools in the left atrial appendage, a small pouch off the left atrium, where it can clot. If that clot leaves, it travels to the brain.
Symptoms, and the problem of having none
Common symptoms are palpitations described as fluttering, thumping or racing, breathlessness on exertion, unusual tiredness, light-headedness, chest discomfort and reduced exercise tolerance.
The difficulty is that a substantial proportion of people have no symptoms at all. Silent AF is often discovered only after a stroke has already happened, which is why opportunistic pulse checks matter.
How to check your own pulse
Place two fingers on the inside of the opposite wrist, below the base of the thumb. Count for 30 seconds and note not just the rate but the rhythm. A normal pulse is regular, like a metronome. In AF it is irregularly irregular, with no repeating pattern, and the strength of individual beats varies.
If you feel this, it needs an ECG. A single-lead ECG from a smartwatch or a home device is a useful screening prompt but is not a diagnosis; a 12-lead ECG or a Holter monitor confirms it.
Types
- Paroxysmal: episodes start and stop on their own, usually within 48 hours to 7 days
- Persistent: lasts longer than 7 days and needs intervention to restore rhythm
- Long-standing persistent: continuous for more than a year
- Permanent: a decision has been made to stop trying to restore normal rhythm
Stroke risk is similar across these types. Paroxysmal AF is not a safe version.
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What causes it
- High blood pressure, the single most common contributor
- Age, with incidence rising sharply after 65
- Coronary artery disease and previous heart attack
- Heart valve disease, especially rheumatic mitral disease, which remains common in India
- Heart failure
- Overactive thyroid
- Obstructive sleep apnoea, strongly linked and frequently missed
- Obesity
- Alcohol, including single heavy episodes, sometimes called holiday heart
- Chronic lung disease
- Acute illness, infection, surgery and electrolyte disturbance
- Excess caffeine or stimulant use in susceptible people
Assessing stroke risk
Doctors use the CHA2DS2-VASc score, which assigns points for congestive heart failure, hypertension, age 75 or above, diabetes, previous stroke or clot, vascular disease, age 65 to 74, and female sex.
Broadly, anticoagulation is recommended for men scoring 2 or more and women scoring 3 or more, and considered at one point lower. Bleeding risk is assessed alongside, but a high bleeding risk is usually a reason to correct modifiable bleeding factors rather than to withhold anticoagulation.
Treatment has three parts
Preventing stroke. This is the priority. Direct oral anticoagulants such as apixaban, rivaroxaban, dabigatran and edoxaban are now first choice for most patients, with warfarin still preferred in mechanical valves and moderate to severe mitral stenosis. Aspirin is not adequate stroke prevention in AF, a point that is still widely misunderstood. For people who cannot take anticoagulants, left atrial appendage occlusion is an option.
Controlling the rate. Beta blockers, or rate-limiting calcium channel blockers such as diltiazem and verapamil, and sometimes digoxin, slow the ventricular response so the heart fills properly.
Restoring the rhythm. Options include antiarrhythmic drugs, electrical cardioversion, and catheter ablation. Ablation has become increasingly effective, particularly in younger patients, in paroxysmal AF and in AF with heart failure. Restoring rhythm does not remove the need for anticoagulation in people whose stroke risk score is high.
The part patients control
Risk factor management changes outcomes measurably:
- Weight loss of 10 percent or more substantially reduces AF burden
- Treating sleep apnoea reduces recurrence after ablation
- Blood pressure control
- Reducing or stopping alcohol, which has a clear dose relationship
- Regular moderate exercise, while avoiding extreme endurance training, which can itself provoke AF
- Treating thyroid disease and diabetes
Seek urgent help if
Chest pain, severe breathlessness, fainting, a very fast pulse with distress, or any stroke sign: sudden facial droop, arm weakness, slurred speech or confusion. A stroke is treatable in the first hours, so time matters more than certainty.
This is general information. Anticoagulation decisions depend on your individual stroke and bleeding risk and must be made with a doctor.