About 2.7 million people are living with atrial fibrillation, an irregular heartbeat that increases their risk for stroke by as much as 5 times that of people who do not have Afib. In this diagram, you can see how the heart muscle quivers during an episode of atrial fibrillation (right). The electrocardiogram (EKG or ECG) shown here also highlights the difference between the steady normal sinus rhythm (left) and the fast, erratic heartbeat in atrial fibrillation (right).

Atrial fibrillation, commonly known as Afib or AF, is an irregular heartbeat caused by an abormal heart rhythm. Normally, the heart sends regular electrical signals from one section to another. In Afib, there are irregular signals sent from the heart's top chambers (the atria). This results in quivering, or fibrillation, of the atria. While AFib itself generally is not life-threatening, complications from Afib can be very serious. When blood stays in the quivering heart chamber, it can clot. Blood clots can travel to organs such as the brain, which can lead to stroke. Approximately 35 percent of people with Afib will go on to suffer a stroke, which is why it is essential to diagnose and treat Afib at the outset.

Afib is the most common heart rhythm irregularity, or cardiac arrhythmia. According to the American Heart Association, about 2.7 million people are estimated to have Afib. People over the age of 65 are more likely to develop Afib, although it can affect anyone.

Understanding the Heart’s Rhythm

To understand Afib, it is essential to understand the normal function of the heart. The heart is the organ responsible for pumping blood through your body. Its pumping action, our “heartbeat,” is stimulated by electrical impulses in the atria chambers. This area is known as the sinoatrial node, or SA node. While all heart tissue is capable of generating such electrical impulses, normally the SA node is most dominant. This is why the SA node is thought of as the heart’s pacemaker – because it keeps the heart in a natural rhythm.

When the SA node is regulating the heart’s rhythm, the heart is in sinus rhythm. This regular pacing ensures that the heart appropriately fills with blood for each beat. A signal from the SA node coordinates the contraction of the atria chambers. Meanwhile, the atrioventricular node (or AV node) serves as the gatekeeper for the electrical impulse generated by the SA node. The AV node transmits the electrical impulses to the heart’s lower chambers (called ventricles), which include strong fibers that contract to help push blood through the heart. The regular movement of blood through the heart is known as the cardiac cycle, and under normal circumstances, occurs with each beat, between 60 to 100 times each minute. This rate may go higher during exercise, but should go back to normal when you are at rest.

An arrhythmia occurs when this process does not go as it should:  The SA node fires extra signals or fires erratically, which stimulates the heart to beat erratically as well. Sometimes other impulses may “escape” the dominant SA node to cause extra beats, or the impulse may create a short circuit that results in series of extra beats. Or the usual coordinated conduction of the impulse from the SA node may fail to contract the atria and may fragment into hundreds of impulses across the upper chamber. If you are experiencing atrial fibrillation, you may be referred to a heart specialist called an electrophysiologist, who is specially trained to determine which type of disruption in the cardiac cycle is causing your atrial fibrillation and how to treat it.

What Does Afib Feel Like?

The symptoms of Afib can be frightening, particularly if you are experiencing them for the first time. Some people report feeling a change in the rhythm of their heart. Their heartbeat may or may not be rapid, and the symptoms may or may not go on for an extended time. Some patients report feeling a fluttering in their chest, or even chest pain, while others say they only got sweaty or felt dizzy or weak during these episodes. Some symptoms come and go, while others may be constant

Talk with Your Doctor or Other Healthcare Professional

Because Afib shares symptoms with several other problems, it is essential to report any symptoms – no matter how minor you think they might be – to your doctor or other healthcare provider. If you have had a stroke or a transient ischemic attack (TIA, or "mini-stroke"), you may want to ask your healthcare team about atrial fibrillation and other stroke risk factors. Your healthcare team can examine you and perform any necessary tests. It is important to have your condition monitored because Afib can increase the risk for other heart problems, including heart failure, as well as your risk of stroke. Fortunately, Afib can be well managed, allowing for a long and full life.

Learn More

You can learn more about Afib, including how it is diagnosed and treated, in the SecondsCount Atrial Fibrillation Center.