Atrial Fibrillation (AFib)

What happens in atrial fibrillation

Normally, each heartbeat starts in the sinus node, the heart's natural pacemaker in the right atrium. The signal spreads across both atria, which contract and push blood into the ventricles, then passes through the AV node to make the ventricles pump.

In AFib, hundreds of disorganized electrical impulses per minute fire across the atria, often starting from the pulmonary veins. The atria quiver (fibrillate) instead of contracting. The AV node lets through only some of these impulses, so the ventricles beat irregularly and often quickly, at 100 to 175 beats per minute or more if untreated.

Two consequences follow:

• Clots: blood pools in the quivering atria, especially in a pouch called the left atrial appendage, where clots can form, travel to the brain and cause a stroke.
• Reduced pumping: the loss of atrial contraction and the fast, irregular rate reduce cardiac output, which can cause breathlessness, fatigue and, over time, heart failure.

Types of AFib

The 2023 US guideline also describes AFib as a progressive disease with stages, from being at risk, through pre-AF changes, to established AFib, to emphasize prevention and early treatment.

Symptoms

• palpitations: a fluttering, racing, pounding or irregular heartbeat
• shortness of breath, especially on exertion
• tiredness and reduced exercise capacity
• dizziness or lightheadedness
• chest discomfort
• anxiety
• frequent urination during episodes

Many people, especially older adults, have no symptoms and are diagnosed from a routine pulse check, ECG or smartwatch alert. Symptoms do not predict stroke risk: silent AFib carries the same risk.

Causes and risk factors

• age: risk rises steeply after 65
• high blood pressure: the most common modifiable risk factor
• obesity
• alcohol: even moderate regular drinking raises risk; binge drinking can trigger episodes ("holiday heart")
• sleep apnea
• heart disease: coronary artery disease, heart attack, heart failure, valve disease (especially mitral valve disease) and heart surgery
• hyperthyroidism
• diabetes, chronic kidney disease and lung disease
• endurance athletics over many years
• acute triggers: infections such as pneumonia, surgery, and stimulants
• genetics: family history increases risk

Diagnosis

• ECG: confirms AFib by showing an irregularly irregular rhythm with no normal P waves.
• Ambulatory monitoring: Holter monitors, patch monitors, event recorders or implantable loop recorders catch intermittent episodes. Smartwatch ECGs can detect AFib, but need confirmation by a clinician.
• Echocardiogram: assesses heart function, valves and atrial size.
• Blood tests: thyroid function, kidney function, electrolytes, blood count.
• Sleep study if sleep apnea is suspected.

Treatment

1. Stroke prevention

Your stroke risk is estimated with the CHA₂DS₂-VASc score, which adds points for congestive heart failure, hypertension, age 75 or over (2 points), diabetes, prior stroke or TIA (2 points), vascular disease, age 65 to 74, and female sex. Anticoagulation is generally recommended for an estimated annual stroke risk of 2 percent or more, which corresponds to a score of 2 or higher in men or 3 or higher in women, and is considered at lower scores.

• Direct oral anticoagulants (DOACs): apixaban, rivaroxaban, edoxaban and dabigatran are preferred for most people. They need no routine blood monitoring.
• Warfarin: still used for people with mechanical heart valves or moderate to severe mitral stenosis.
• Aspirin is not recommended for stroke prevention in AFib.
• Left atrial appendage occlusion: a device that closes the appendage, an option for people who cannot take long-term anticoagulants.

2. Rate control

Medicines slow the heart rate to improve symptoms and protect heart function:

• beta blockers (such as metoprolol, bisoprolol)
• non-dihydropyridine calcium channel blockers (diltiazem, verapamil), avoided in people with weak heart function
• digoxin in some cases

3. Rhythm control

Aims to restore and maintain normal rhythm:

• cardioversion: an electrical shock under sedation, or medicine, to reset the rhythm
• antiarrhythmic medicines: such as flecainide, propafenone, sotalol, dronedarone and amiodarone
• catheter ablation: thin tubes passed to the heart through a leg vein isolate the pulmonary veins with heat, cold or pulsed-field energy. It is more effective than medicines at keeping normal rhythm and is now a first-line option for selected people, including many with paroxysmal AFib and some with heart failure.

Early rhythm control, within a year of diagnosis, has been shown to reduce cardiovascular events in some patients.

4. Risk factor management

This is now recognized as a core part of AFib treatment, not an extra:

• weight loss of 10 percent or more in people with obesity reduces AFib burden
• cutting alcohol substantially or stopping
• blood pressure, blood sugar and cholesterol control
• treating sleep apnea
• regular moderate exercise
• stopping smoking

Complications

• stroke and TIA
• heart failure, including tachycardia-induced cardiomyopathy from a persistently fast rate
• cognitive decline and dementia, partly from small, silent strokes
• bleeding from anticoagulants

Living with AFib

Many people with AFib live full, active lives. Take anticoagulants exactly as prescribed and do not stop them without talking to your doctor. Tell dentists and surgeons you take a blood thinner. Learn to check your pulse, and keep a record of episodes and triggers. Ask about a written plan for what to do if a fast episode starts.

Frequently asked questions

What is atrial fibrillation?

Atrial fibrillation is an irregular, often rapid heart rhythm caused by chaotic electrical signals in the upper chambers of the heart. The atria quiver instead of contracting properly, which can cause palpitations and breathlessness and increases the risk of blood clots and stroke.

What are the first signs of AFib?

Common first signs are a fluttering or pounding heartbeat, an irregular pulse, breathlessness, tiredness, dizziness or reduced ability to exercise. Many people have no symptoms and are diagnosed from a routine ECG, pulse check or smartwatch alert.

Is AFib dangerous?

AFib itself is rarely immediately life-threatening, but it raises the risk of stroke about fivefold and can lead to heart failure. With blood thinners, rate or rhythm control, and risk factor management, these risks are greatly reduced.

Can AFib go away on its own?

Paroxysmal episodes often stop on their own within hours or days. AFib triggered by a temporary cause, such as an infection, surgery or an overactive thyroid, may not return once the cause is treated. In most people, though, AFib tends to recur and can progress without treatment.

What triggers AFib episodes?

Common triggers include alcohol, lack of sleep, stress, dehydration, large meals, caffeine in sensitive people, stimulant medicines, infections and intense exercise. Underlying high blood pressure, obesity and sleep apnea make episodes more likely.

Do I need a blood thinner for AFib?

Most people with AFib and at least one additional stroke risk factor benefit from a blood thinner. Your doctor will use the CHA₂DS₂-VASc score and bleeding risk to decide. Aspirin is not an effective substitute.