What causes atrial fibrillation?
Normally each heartbeat starts in the sinus node of the right atrium. In AFib, chaotic electrical signals—usually from around the pulmonary veins—make the atria quiver hundreds of times a minute, and the ventricles beat irregularly. Risk factors include age, high blood pressure, heart failure, valve disease, diabetes, obesity, heavy drinking, an overactive thyroid and obstructive sleep apnea.
Symptoms and diagnosis
AFib can cause palpitations, shortness of breath, dizziness, fatigue and reduced exercise capacity, but many people have no symptoms. It's diagnosed with an ECG; episodes that come and go (paroxysmal AFib) are caught with a 24-hour Holter or patch monitor. In the 2019 Apple Heart Study, 34% of people who got an irregular-pulse alert from their smartwatch were confirmed to have AFib on an ECG patch. An alert isn't a diagnosis—it's a signal to see a doctor.
How is stroke prevented in AFib?
Blood can pool in the atria and form clots that travel to the brain. Risk is assessed with the CHA2DS2-VASc score, which counts heart failure, high blood pressure, age, diabetes, prior stroke, vascular disease and sex. At higher risk, doctors prescribe warfarin or a direct oral anticoagulant (DOAC).
Rate and rhythm control
- Rate control: beta-blockers or calcium channel blockers slow a fast heartbeat.
- Rhythm control: antiarrhythmic drugs or electrical cardioversion restore normal rhythm, and catheter ablation blocks signals around the pulmonary veins. In the 2020 EAST-AFNET 4 trial, starting rhythm control within a year of diagnosis led to fewer cardiovascular events (HR 0.79).
- Risk-factor management: weight loss, cutting back on alcohol, and treating blood pressure and sleep apnea reduce recurrences.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- Is atrial fibrillation dangerous?
- AFib itself is rarely immediately life-threatening, but it raises the risk of stroke about fivefold and can weaken the heart over time, so it needs evaluation and often treatment.
Sources reviewed: 2026-10-25
References
- Lloyd-Jones, D. M., et al. (2004). Lifetime risk for development of atrial fibrillation: the Framingham Heart Study. Circulation, 110(9), 1042–1046.
- Perez, M. V., et al. (2019). Large-scale assessment of a smartwatch to identify atrial fibrillation. New England Journal of Medicine, 381(20), 1909–1917.
- Kirchhof, P., et al. (2020). Early rhythm-control therapy in patients with atrial fibrillation. New England Journal of Medicine, 383(14), 1305–1316.