What is Atrial Fibrillation?

June 19, 2024
Avatar for Jyoti Kinghorn, PhDJyoti Kinghorn, PhD
ECG is the main test for detecting atrial fibrillation

Atrial fibrillation is a type of arrhythmia of the heart that originates in the heart’s upper chambers (atria). The heart beats too slow, too fast, or has an irregular rhythm.

Atrial fibrillation can lead to complications such as weakening of the heart, heart failure, formation of blood clots, and strokes. Atrial fibrillation is the cause of about one in seven strokes.

How atrial fibrillation affects the heart

How the heart normally pumps blood

Normally, a group of cells called the sinoatrial (SA) node generates electrical signals that activate the heart to pump blood. First, a signal from the SA node activates the heart’s upper two chambers called the atria. The signal then travels down the heart to the lower two chambers called the ventricles.

In response to this electrical stimulus, the atria contract for a short time pumping blood into the ventricles. This is followed by the ventricles contracting, which pumps blood to the rest of the body. The two pumping actions complete a cardiac cycle and create a heartbeat.

The SA node sends between 60 and 100 electrical stimuli to the heart every minute, each resulting in a heartbeat. In a healthy heart beating at 75 beats/minute, each cardiac cycle lasts about 0.8 seconds.

What goes wrong during atrial fibrillation?

In atrial fibrillation, electrical signals to the heart come from outside the SA node causing the upper ventricles to contract chaotically. Instead of pumping out blood with adequate contractions, the atria quiver. The chaos carries over to the ventricles which also contract irregularly. Based on how fast the impulses come, the atria and ventricles may be unable to pump out blood efficiently. This can lead to a pooling of blood in the atria, which can then result in the formation of blood clots. Blood clots when pumped out of the heart can travel through the body and cause dangerous complications such as strokes.


Atrial fibrillation is the most common type of treated arrhythmias of the heart. It is more common in older adults. The median age of atrial fibrillation is 75, though the risk starts increasing after the age of 40 and more than doubles after the age of 65. Individuals under the age of 40 can also develop atrial fibrillation.
Currently, over 6 million people in the US have atrial fibrillation. About 800,000 of them are under 40. The CDC estimates that by 2030, 12.1 million Americans will have atrial fibrillation.

Symptoms of atrial fibrillation

Atrial fibrillation may not have any symptoms, or the symptoms may not be noticeable to the patient.

When present, symptoms of atrial fibrillation include:

  • Irregular heartbeat
  • Heart palpitations such as fluttering, pounding, or rapid heartbeats
  • Shortness of breath
  • Angina (chest pain)
  • Extreme fatigue
  • Lightheadedness, dizziness, or fainting
  • Weakness

An electrocardiogram (ECG) is the main method for diagnosing atrial fibrillation.

Atrial fibrillation risk factors

Structural heart problems

Often, issues with the structure of the heart can cause atrial fibrillation. These include:

  1. Congenital heart defects – heart problems that develop in the fetus during pregnancy.
  2. Heart valve disease- heart valves do not close fully, or their openings become narrowed.
  3. Coronary artery disease (also called ischemic heart disease) – a blockage in the arteries that obstructs blood flow.
  4. Sick sinus syndrome- heart rate issues caused by an impaired SA node.

Other health issues that can cause atrial fibrillation include lung diseases, thyroid diseases, high blood pressure, and diabetes.

Obesity, smoking cigarettes, excessive alcohol consumption, excessive caffeine consumption, illegal drug use, and advancing age increase the risk of atrial fibrillation.

How long does atrial fibrillation last?

Atrial fibrillation can be temporary (paroxysmal), lasting only about a week and resolving on its own. Or, it can be persistent, lasting over a week and requiring treatment to resolve. It is said to be long-standing persistent when it lasts longer than 12 months. A permanent atrial fibrillation is where a medical decision is made not to pursue further action to resolve the arrhythmia. 


To treat atrial fibrillation, your physician may prescribe:

  • Medications that help control the heart’s rhythm and rate.
  • Cardioversion, a method to reset the heart’s rhythm and restore the natural rhythm by low-energy shocks or medications.
  • Medications that are blood-thinning and prevent the formation of blood clots.
  • Surgery to resolve structural issues.
  • Lifestyle changes that support good heart health.

The information provided in our blog posts is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog.

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