Patient overview

What causes atrial fibrillation?

Atrial fibrillation (AF) is a common heart rhythm condition where the heart’s upper chambers (the atria) beat in a fast, irregular, uncoordinated way. Many people are told they have AF and immediately ask: “Why did this happen to me?”

The most important idea is that AF usually has more than one cause. In many people, the heart becomes more vulnerable over time (because of blood pressure, sleep issues, weight, ageing, or heart structure), and then a shorter-term trigger (like an infection, dehydration, or alcohol) can bring on an episode.

Education, not diagnosis: this site explains common causes and contributors. Your personal causes depend on your medical history, examination, ECG, blood tests, and (often) an ultrasound of your heart (echocardiogram).

How doctors think about “causes”

Doctors often group AF causes into:

Long-term contributors

High blood pressure (often over many years)
Sleep apnea and breathing problems during sleep
Excess weight and metabolic health issues
Heart valve problems or heart failure/stiffness
Age-related changes in atrial tissue

Short-term triggers

Infections and inflammation (e.g., chest infections)
Dehydration, low potassium or magnesium
Alcohol (especially binge drinking) and stimulants
Thyroid overactivity
After surgery or major illness

Why identifying causes matters

Finding contributing causes is not about blame. It is about identifying fixable drivers. Many causes are modifiable (blood pressure control, sleep apnea treatment, weight loss, alcohol reduction). Addressing these factors can reduce AF episodes and improve overall health.

Example rhythm video (AF)

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Example ECG showing atrial fibrillation (educational, de-identified). Typical features include an irregularly irregular pulse and no consistent P waves.

Explore causes (one page per cause)

Cause category	What it means	Go to page
High blood pressure	Long-term pressure load changes the heart and stretches the atria.	High blood pressure
Heart structure & valves	Valve disease and structural heart changes enlarge/irritate the atria.	Structure & valves
Electrical system	How heart wiring and “misfiring” can lead to AF.	Electrical system
Lifestyle	Alcohol, stimulants, weight, fitness extremes, stress.	Lifestyle
Sleep & breathing	Sleep apnea and nighttime oxygen swings strongly contribute.	Sleep & breathing
Illness & temporary triggers	Infection, surgery, dehydration, electrolytes, thyroid.	Illness triggers
Genetics	Inherited tendency, early-onset AF, family patterns.	Genetics
Ageing	Age-related atrial changes can lower the threshold for AF.	Ageing

If you want risks and complications: this site focuses on causes. For stroke risk, heart failure risk, and what AF can lead to, see atrialfibrillationrisks.com.