Causes and Risk Factors of Atrial Fibrillation

Reviewed by: HU Medical Review Board | Last reviewed: January 2024

Atrial fibrillation, or AFib, is when the heart beats at an irregular or too fast pace. It is the most common form of arrhythmia and affects millions of people worldwide.1-3

Instead of consistent, regular heartbeats, AFib leads to chaotic, erratic heartbeats. Symptoms of AFib include heart palpitations, fatigue, shortness of breath, and dizziness, to name a few. Knowing what causes this type of heart condition can help you understand your risk.1-3

How the heart works

First, it might be helpful to understand how the heart works. There are 4 chambers in the heart – 2 upper chambers (atria) and 2 lower chambers (ventricles). In addition to these 4 chambers, the atrium has what is called the sinoatrial (SA) node. These parts work together to pump blood to the rest of the body.1,2

The SA node is in charge of sending electrical impulses through the atria, causing them to contract and pump blood into the ventricles. The electrical impulses then reach the atrioventricular (AV) node, before moving to the ventricles. The ventricles then contract and send blood out to the body.1,2

In AFib, the atria and ventricles do not work in the coordinated way that they should. This results in an irregular and often rapid heartbeat.1,2

Causes of atrial fibrillation

There are several known causes of AFib, but experts do not yet know all the possible causes. Known causes include:1-4

  • Congenital heart condition (a condition you are born with)
  • Heart conditions like heart attack, high blood pressure, and heart valve disease
  • Viral infections
  • Overactive thyroid
  • Lung problems
  • Obstructive sleep apnea

Risk factors for AFib

While the exact cause of AFib is not clear in every case, certain factors can increase a person’s risk:1-4

  • Older age
  • Pre-existing heart conditions
  • High blood pressure
  • Family history
  • Obesity
  • Lifestyle factors

Older age

As you grow older, your risk of developing AFib increases. This is partly due to the wear and tear on the heart's electrical system over time. Inflammation, changes in the heart tissue, and fibrosis may be factors as well.1-3

Pre-existing heart conditions

People with existing heart conditions are more at risk for AFib. These conditions may include coronary artery disease (CAD), heart valve disorders, and congenital heart defects. They can alter the heart's structure and increase the chance of irregular heartbeats.1-4

High blood pressure

High blood pressure, also called hypertension, is a major risk factor for AFib. The increased pressure in the arteries puts extra strain on the heart. This can impact the heart’s structure and how it works.1-4

Family history

Experts believe that there may be a genetic aspect to AFib. If you have a family history of AFib, you may be more likely to develop the condition.1-4


Good heart health depends on maintaining a healthy weight. Obesity can contribute to AFib by increasing cholesterol, increasing blood pressure, and placing extra stress on the heart. Someone with obesity may have sleep apnea (though sleep apnea can also occur in someone with normal weight), which also is linked to AFib.1,2,4

Lifestyle factors

Unhealthy lifestyle habits, such as drinking too much alcohol and smoking, can increase the risk of AFib. Alcohol (especially in large quantities) can affect the heart's electrical signals. Smoking affects the body’s vascular systems, which impacts heart function.1-4

Be aware of AFib symptoms

Atrial fibrillation can lead to serious complications like stroke or heart attack if left untreated. If you have AFib symptoms, talk to your doctor as soon as possible.1-4

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