Atrial Fibrillation
Atrial Fibrillation

Atrial Fibrillation Causes and Risk Factors

Atrial fibrillation is most often caused by changes to the heart’s tissue or the electrical signaling that helps the heartbeat. To better understand atrial fibrillation, it helps to first understand what causes it.

What causes atrial fibrillation?

Typically, the electrical signals that make the heart pump start in the sinoatrial node, a special area of the upper right chamber of the heart called the right atrium. The signal makes both the right atrium and the left atrium contract. That action pumps blood to the lower heart chambers, or ventricles. The electrical signal then travels further down the heart, signaling the ventricles to contract.

In atrial fibrillation, unusual electrical signals in the upper chambers interrupt this typical process. The unusual signals cause the upper chambers of the heart to contract irregularly, which makes your heart’s upper and lower chambers unable to work together to effectively pump blood.

When the heart’s tissue or electrical signaling is damaged, the regular pumping of the heart muscle can become fast and irregular. Most often, this type of damage to the heart is caused by other conditions such as high blood pressure and coronary heart disease. However, other factors can lead to changes in heart tissue or changes to the heart’s electrical signaling that can cause atrial fibrillation to develop.

Illustration of atrial fibrillation
This image shows the electrical system of the heart during atrial fibrillation and includes a picture of an electrocardiogram in the upper right corner showing the irregular electrical impulses that are measured during A-fib. Medical Illustration Copyright © 2022 Nucleus Medical Media, All rights reserved

Changes in heart tissue

Factors such as aging, heart disease, infection, or genetics can affect heart tissue and keep the heart cells from contracting in rhythm. Tissue changes that impact your heart’s ability to contract in rhythm may include  fibrosis inflammation ; stretching, thinning or thickening of the heart walls; reduced blood flow to the heart; or a buildup of protein, cells, or minerals in heart tissue.

Changes to the heart's electrical signaling

Usually, a “trigger” heartbeat sets off atrial fibrillation. Electrical signals from this trigger beat may cause the heart to keep beating slower or faster than usual. Sometimes, electrical signals start an abnormal loop, telling the heart to contract over and over. This can create the fast, irregular heartbeat that defines atrial fibrillation.

Changes in the heart’s electrical signaling can be caused by differences in the structure of the heart, heartbeats that happen early or too often, typical heart rate adjustments, patches of heart tissue that conduct the signal quickly or slowly, or repeated stimulation of specific areas of the heart.

What raises the risk of atrial fibrillation?

Age, family history and genetics, lifestyle, heart disease or other medical conditions, race, and surgical history can all raise your risk of developing the structural and electrical issues that lead to atrial fibrillation. Even in a healthy heart, a fast or slow heart rate — from exercising or sleeping, for example — can trigger atrial fibrillation. Sometimes, though, atrial fibrillation happens for no obvious reason.


The risk of atrial fibrillation increases as you get older, especially when you are over age 65. Atrial fibrillation is rare in children.

Family history and genetics

If someone in your family has had atrial fibrillation, you have a higher risk of developing atrial fibrillation, too. Scientists have found some  genes  with  mutations  that raise the risk of atrial fibrillation. Some of these genes influence fetal organ development or cells in the heart that regulate heart rhythm.

Sometimes these genetic patterns are also linked to heart disease. Some genetic factors may raise the risk of atrial fibrillation in combination with factors such as age, weight, or sex.

Lifestyle factors

Some lifestyle choices can raise or lower your risk of atrial fibrillation.

  • Alcohol consumption in large amounts, especially binge drinking, raises your risk of atrial fibrillation. Even modest amounts of alcohol can trigger atrial fibrillation in some people.
  • Illegal drugs, such as cocaine and other street drugs, can trigger atrial fibrillation or make it worse.
  • Physical activity, for example, participating in endurance sports or physically working hard, may lead to a higher risk of atrial fibrillation for some people, especially competitive athletes and men. At the same time, moderate physical activity can have a protective effect that can lower your risk of atrial fibrillation, as well as other heart diseases.
  • Smoking increases the risk of atrial fibrillation, according to many studies. The risk appears to be higher the longer you smoke and decreases if you quit. Exposure to secondhand smoke, even in the womb, can increase a child’s risk of developing atrial fibrillation.
  • Stressful situations, panic disorders, and other types of emotional stress may be linked to a higher risk of atrial fibrillation.

Other medical conditions

Many other medical conditions, including heart, lung, and sleep disorders, can raise your risk of atrial fibrillation. Common conditions that increase your risk include:

Many medicines, including over-the-counter ones and stimulants, may also increase your risk, especially if you have other risk factors for atrial fibrillation.


In the United States, atrial fibrillation is more common among white people than  among Black or African American, Hispanic, or Asian people. Although people of European ancestry are more likely to develop the condition, Black or African American people with atrial fibrillation are more likely to have serious complications such as stroke, heart failure, or heart disease where blood flow (and oxygen flow) is reduced.


You may be at risk of atrial fibrillation in the early days and weeks after surgery on your heart, lungs, or esophagus. For example, heart surgery to correct a congenital heart defect can raise the risk of atrial fibrillation. This risk remains even years after a childhood surgery. It is also a risk if someone has surgery as an adult to correct a lifelong condition.

Can you prevent atrial fibrillation?

Your provider may recommend that you take steps to help lower your risk of atrial fibrillation.

Your Guide to a Healthy Heart

Your Guide to a Healthy Heart

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