What Are the Causes and Triggers of Atrial Fibrillation?

Written by Sarah Pozniak, MD | Reviewed by Patricia Pinto-Garcia, MD, MPH

Updated on January 12, 2024print_outlinedemail_outlined

Key takeaways:

Atrial fibrillation (AFib) is a common heart rhythm problem that’s more likely to happen as people get older. It causes an abnormal — and sometimes fast — heartbeat.
It’s not always clear what causes AFib, and there are many risk factors. Common ones include family history, smoking, alcohol use, and other medical problems like high blood pressure and diabetes.
If you have AFib, you can prevent it from getting worse by avoiding common triggers and following a heart-healthy lifestyle.

A close-up of a stethoscope on an ECG. sudok1/iStock via Getty Images Plus

Atrial fibrillation (AFib) is a type of abnormal heart rhythm (arrhythmia). In fact, it’s the most common type of treated abnormal heart rhythm in the United States. Up to 6 million people in the U.S. have it.

AFib happens when the heart’s upper chambers (the atria) beat fast and irregularly. This causes blood to move less effectively through the heart. Over time, this can damage the heart muscle and increase the risk of blood clots. The good news is that AFib is treatable.

Here we’ll review the causes and triggers of AFib — and what you can do to prevent it from getting worse.

What causes atrial fibrillation?

Atrial fibrillation is caused by changes in the heart’s electrical system or by damage to the heart tissue. The heart is powered by an electrical impulse that starts at the sinoatrial (sinus) node. The sinoatrial node is a group of specialized cells that can generate electrical signals. It sits in between the top chambers of the heart (atria). The two atria of the heart contract in response to the electrical signal made by the sinoatrial node.

This electrical signal then travels from the sinoatrial node to the atrioventricular node and then along other nerves to the rest of the heart. As the electrical signal travels through the heart, the rest of the heart muscle contracts (beats) in a coordinated motion. This allows the heart to pump blood to the body.

AFib develops when the sinoatrial node isn’t able to generate a normal electrical impulse. This causes the atria of the heart to contract (beat) irregularly. The sinoatrial node usually stops working well because of other conditions that affect the heart.

Some people are more likely to develop atrial fibrillation than others, especially if they have one of these conditions.

Risk factors for atrial fibrillation

Here are some things that can put people at risk for developing atrial fibrillation:

Older age
Family history of atrial fibrillation
European ancestry
Obesity
Smoking
Alcohol use
Stress

Other long-term medical conditions can also increase someone’s risk, including:

High blood pressure
Diabetes
Obstructive sleep apnea
Chronic kidney disease
Other types of heart disease, such as congenital heart disease, coronary artery disease, heart failure, or a heart valve problem
Cardiomyopathy
Pericarditis
Overactive thyroid gland