What is atrial fibrillation (AFib)?

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Dr. Theodore D. Richards, MD
Cardiologist (Heart Specialist)

Atrial fibrillation or AFib is the most common type of irregular heart beat. It occurs when the upper chambers of the heart (atria) don’t beat in synchronization with the lower chambers (ventricles) of the heart. AFib can be fast or slow and cause symptoms such as fainting and dizziness. AFib can also cause blood pooling in the left atrium where a blood clot can form. If the blood clot becomes loose, it can lodge in an artery near the brain, depriving it from oxygen and causing a stroke.

Dr. Charles A. Joyner, MD
Cardiac Electrophysiologist

Atrial fibrillation (AF) is a condition where the top chambers of the heart demonstrate irregular electrical flow and, therefore, beat chaotically. It forces these chambers out of synchrony with the main pumping chambers of the heart.

Columbia University Department of Surgery
Administration Specialist

Atrial fibrillation occurs when the atrium contracts irregularly or with one portion contracting well before or after another. When this happens the atrium cannot push blood into the ventricles in the normal manner and your heart may feel like it is racing.

Atrial fibrillation is a common arrhythmia that affects about 2.2 million people in the United States. For reasons that aren't fully understood, the upper chambers of the heart periodically quiver erratically. As a result, blood swirls around and pools inside the upper chambers, especially the left atrium. The stagnant blood in the left atrium may form clots that can cause a stroke if they break loose and make their way to the brain.

Texas Cardiac Arrhythmia Institute
Administration Specialist

Atrial fibrillation, or a-fib, is a common cardiac arrhythmia, or heart-rhythm disorder. It affects 3 million Americans.

This abnormal heart rhythm occurs when several electrical impulses in the heart fire simultaneously instead of systematically. This causes a fast and haphazard heartbeat.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Atrial fibrillation (AF) is an irregular heartbeat in which the upper chambers of the heart, called the atria, quiver instead of contracting normally. Watch this animation to learn more about AF, most common cardiac arrhythmia.

Atrial fibrillation is an irregular beating of the heart. This is the most common irregular heart rhythm and a risk factor for ischemic stroke.

Atrial fibrillation is a type of arrhythmia (irregular, or abnormally fast or slow, heartbeats) that can cause rapid, irregular beating of the heart's upper chambers. Blood may pool and clot inside the heart, increasing the risk for heart attack and stroke.

The presence of the CDC logo and CDC content on this page should not be construed to imply endorsement by the US Government of any commercial products or services, or to replace the advice of a medical professional. The mark “CDC” is licensed under authority of the PHS.

Piedmont Heart Institute
Administration Specialist

Atrial fibrillation, or AF, is the most common type of arrhythmia. An arrhythmia is a problem with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.

AF occurs when rapid, disorganized electrical signals cause the atria, the two upper chambers of the heart, to fibrillate. The term "fibrillate" means to contract very fast and irregularly.
In AF, blood pools in the atria and isn't pumped completely into the ventricles, the heart's two lower chambers. As a result, the heart's upper and lower chambers don't work together as they should.

Often, people who have AF may not feel symptoms. However, even when not noticed, AF can increase the risk of stroke. In some people, AF can cause chest pain or heart failure, particularly when the heart rhythm is very rapid.

AF may occur rarely or every now and then, or it may become a persistent or permanent heart rhythm lasting for years.

This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.

Dr. Devender N. Akula, MD
Cardiologist (Heart Specialist)

So the heart normally beats with a regular rate and rhythm. In atrial fibrillation, the top chambers of the heart beat irregularly. It's something that we are seeing more commonly now and as people get older, it seems to happen more frequently. For example the prevalence is less than 2 percent in people who are less than 65 years old and above 65 the prevalence increases to about 9-10 percent.

Trinity Health is a Catholic health care organization that acts in accordance with the Catholic tradition and does not condone or support all practices covered in this site. In case of emergency call 911. This site is educational and not a substitute for professional medical advice, always seek the advice of a qualified healthcare provider.

Dr. James C. Ong, MD
Cardiologist (Heart Specialist)

It’s the most common sustained arrhythmia in Americans, but many people are not aware they have it. Cardiologist James Ong, MD explains the risks and potential consequences of this condition.

Learn about this common rhythm disturbance of the heart, including potential complications and treatment options. Watch this video with cardiovascular surgeon Gregory Fontana, MD from Los Robles Hospital & Medical Center.

Dr. Donald S. Rubenstein, MD
Cardiologist (Heart Specialist)

Atrial fibrillation is a disorganized rhythm of the upper chambers of the heart. Symptoms can range widely among different patients, being unnoticeable in some, while others may experience palpitations, shortness of breath, chest discomfort, weakness and or dizziness. In some patients, atrial fibrillation may also lead to congestive heart failure or stroke.

The contents of this website are for informational purposes only and are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Nor does the contents of this website constitute the establishment of a physician patient or therapeutic relationship. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Intermountain Healthcare
Administration Specialist

If your heart sometimes beats unevenly, you might be experiencing atrial fibrillation. Atrial fibrillation is the most common heart rhythm problem in the United States. Along with creating uncomfortable symptoms, it can also increase your risk of other serious medical conditions:

  • Other heart rhythm problems
  • Heart failure
  • Stroke
Sigma Nursing
Administration Specialist

Atrial fibrillation is a medical emergency that occurs when the upper chambers of the heart beat erratically, quickly, and out of synch with the lower chambers. Because the heart doesn't pump blood well under these conditions, the body suffers from poor blood circulation. The complications that result from atrial fibrillation may be life threatening, though the condition itself isn't usually considered to be.

SCAI
Administration Specialist

You can think of your heart as having its own internal pacemaker. A series of electrical impulses causes the chambers of the heart to contract in a carefully timed sequence. This is your heartbeat. Atrial fibrillation (AF) is a condition in which the electrical system in the heart does not function properly. The two small upper chambers of the heart (the atria) quiver instead of beating normally. This results in blood not being pumped completely out of the chamber, so the blood may pool and clot within the top chambers of the heart (the ventricles). While atrial fibrillation does not always have serious complications, it can result in stroke or heart failure.

Dr. Mowaffak Atfeh, MD
Cardiologist (Heart Specialist)

Mowaffak Atfeh, MD from Oak Hill Hospital, explains that atrial fibrillation refers to an irregular heartbeat in this video.

Dr. Mohamed Djelmami Hani, MD
Cardiologist (Heart Specialist)

Atrial fibrillation is a common heart rhythm disorder. Since the name is difficult to recall for most people, you will often hear it called AF or A-fib. It is the most common arrhythmia heart rhythm disorder seen by physicians and the most common rhythm causing hospital admission. More than two million people in the United States have atrial fibrillation.

Atrial fibrillation (AF) is an irregular and often rapid heartbeat that is caused by disorganized electrical activity. Normally the pumping of the heart is initiated at the upper portion of the heart and sent downward in a regular pattern, resulting in the typical heartbeat. In atrial fibrillation, this regular pattern is disrupted, and therefore the heart doesn't pump as expected.

Scripps Health
Administration Specialist

The most common form of abnormal heart rhythm is atrial fibrillation. Characterized by a very rapid, irregular rhythm in the upper or atrial chambers of the heart, atrial fibrillation is more common with age.

Dr. Audrey K. Chun, MD
Geriatric Medicine Specialist

Atrial fibrillation (AFib) affects more than 2 million Americans. Because it causes the upper chambers of the heart (atria) to beat in an irregular pattern that isn't coordinated with the lower chambers (ventricles), blood flow to the body can be hampered, leading to symptoms such as chest pain, shortness of breath and fatigue. It also can lead to a pooling of blood, which can result in clots that could break free and wind up in the brain.

The biggest health concern for patients with AFib is the potential increase in the risk for stroke. For patients with heart valve conditions, such as mitral valve stenosis, or a prior history of stroke or transient ischemic attack (TIA), that risk could be quite high. Other factors, such as high blood pressure, heart failure, diabetes and advancing age, all increase the risk of stroke.

Age and cardiovascular disease are the strongest predictors of AFib. You may be at risk if you've had a heart attack or heart failure, or have other structural problems with your heart, such as valve disease.

Penn Medicine
Administration Specialist

Approximately 2.5 million Americans experience atrial fibrillation (AFib) each year. This common heart disorder occurs when electrical signals in the heart become irregular, causing the heart to beat out of rhythm. The normal range for a heart rate is 60 to 100 beats a minute, while the heart rate in atrial fibrillation may range from 100 to 175 beats a minute.

Dr. Stephen W. Mester, MD
Cardiologist (Heart Specialist)

Age can play a part in developing atrial fibrillation, says cardiologist Stephen Mester, MD, of Brandon Regional Hospital. In this video he describes the cause behind an irregular heartbeat and palpitations.

Dr. Richard T. Leshner, DO
Cardiologist (Heart Specialist)

Atrial fibrillation (AFib) is an irregular rhythm of the heart. It originates in the upper chambers. It decreases the effectiveness of pumping of the heart. The heart doesn’t pump as efficiently, so the person has less energy.

There are many technologies that can be used to bring the heart back to  normal, regular heart rhythm. Doctors can often return people to regular rhythm without drugs or with minimal medications and improve cardiac output and the quality of their life. One in five people over age 65 will develop atrial fibrillation in their lifetime.

Trinity Health is a Catholic health care organization that acts in accordance with the Catholic tradition and does not condone or support all practices covered in this site. In case of emergency call 911. This site is educational and not a substitute for professional medical advice, always seek the advice of a qualified healthcare provider.

Dr. Benjamin T. Cohen, MD
Cardiologist (Heart Specialist)

Atrial fibrillation (AFib) is a chaotic contraction pattern in the upper chambers of the heart. In this video, Ben Cohen, MD, a cardiologist at West Hills Hospital, explains how A-fib can lead to cerebral embolisms.

Dr. Suman Pasupuleti, MD
Cardiac Electrophysiologist

Atrial fibrillation is a heart rhythm abnormality that causes irregular heart rhythm. Watch this video to learn more about interventional cardiology from Suman Pasupuleti, MD at Citrus Memorial Hospital.

Dr. Robert J. Subbiondo, MD
Cardiologist (Heart Specialist)

Atrial fibrillation is a rhythm disturbance in the heart that causes it to pump faster and irregularly, says Robert Subbiondo, MD, from Blake Medical Center. Learn what this means for your heart health by watching this video.

Los Robles Regional Medical Center
Administration Specialist

Atrial fibrillation is an abnormal heart rhythm. In this video, Susan Johnson, director of cardiovascular services at Los Robles Hospital & Medical Center, explains what the source of this issue is.

Dr. Ronald M. Firth, MD
Family Practitioner

In atrial fibrillation (also called Afib), your heart beats rapidly or unevenly. Here’s a comparison of how the heart beats normally and what happens with Afib:

  • In a normal heart electrical impulses are generated by the SA node, a small area in the hearts right upper chamber (atrium). As the electrical impulses travel smoothly through the heart, the two upper chambers (the atria) squeeze at the same time to pump blood down to the lower chambers (the ventricles). Then the two ventricles squeeze at the same time, pumping blood to your lungs to pick up oxygen and to the rest of your body. The heart beats regularly and evenly, about 60 to 100 times a minute.
  • With Afib, electrical impulses come too rapidly and don’t travel smoothly. Instead, many of the impulses cycle around within the atria. This can cause the atria to quiver, and in turn the ventricles can beat rapidly. The atria and ventricles don’t coordinate in a normal rhythm, and the heart can beat rapidly, up to 300 times per minute.

Afib can come and go—returning to normal after a few minutes or hours—or it can persist.

Baptist Health South Florida
Administration Specialist

Atrial fibrillation (AFib) is an irregular heartbeat during which the heart muscles fail to contract in a strong and rhythmic way. When a heart is in AFib, it may not be pumping enough oxygen-rich blood out to the body.

A racing, pounding heartbeat that can hit for no apparent reason should never be ignored. And it can be especially serious when the accelerated or irregular heartbeat presents with shortness of breath after light physical activity or lightheadedness, dizziness, or unusual fatigue.

Studies have shown that too many people affected by AFib do not realize they have it and may delay getting help.

Atrial fibrillation (AFib) is the most common type of cardiac arrhythmia, which is the incidence of the heart beating irregularly. AFib is caused by a multitude of factors, some environmental, some behavioral and some genetic. It is often found in those with atherosclerosis, angina, hypertension, and in people with lung problems, including asthma, emphysema, pulmonary blood clots and chronic obstructive pulmonary disease (COPD). AFib is also commonly associated with diseases such as stroke and heart failure, and as AFib becomes permanent in a person, mortality rates increase.

Dr. Douglas E. Severance, MD
Family Practitioner

Atrial fibrillation, also known as atrial fib, A. Fib, or AF, is the most common type of abnormal heart rhythm. Atrial fibrillation causes the two upper chambers of the heart (called the atria) to fibrillate—or beat fast and irregularly—out of sync with the two lower chambers (the ventricles) of the heart. Your heart muscle’s main job is to keep your blood pumping through the body. Valves in the heart work to make sure your blood moves in a forward direction through the blood vessels, which function like pipes and circulate the blood around the body. However, the irregular heartbeat of atrial fibrillation interrupts the normal flow of blood through the heart.

Dr. Jorge A. Alvarez, MD
Interventional Cardiologist

Watch as Jorge Alvarez, MD, an interventional cardiologist at Methodist Hospital, describes the heart condition called atrial fibrillation (Afib)--and the more serious heart problem it can lead to.

Dr. Roger K. Muse, MD
Cardiac Electrophysiologist

Atrial fibrillation is an arrhythmia that occurs in the top part of the heart. In this video, Roger Muse, MD, cardiac electrophysiologist with Metropolitan Methodist Hospital, details the symptoms and treatment options for atrial fibrillation.

Dr. Matthew T. Levy, MD
Cardiac Electrophysiologist

Atrial fibrillation (AFib) is an arrhythmia that involves the upper parts of the heart. In this video, Matt Levy, MD, a cardiologist at Good Samaritan Hospital, explains the way in which AFib affects your heartbeat.

Dr. Syed T. Zaidi, MD
Interventional Cardiologist

The erratic beating of the heart is known as atrial fibrillation (Afib). In this video, Syed Zaidi, MD from Southern Hills Hospital & Medical Center, shares more about the disorder and the danger Afib poses.

Dr. Hari C. Kannam, MD
Cardiologist (Heart Specialist)

Atrial fibrillation (AFib) is a rhythm problem in the heart. In this video, interventional cardiologist Hari Kannam, MD, of Citrus Memorial Hospital, explains how treatment options differ for AFib based on how hard it is to control the heart rhythm.

Dr. Robert S. Fishel, MD
Cardiac Electrophysiologist

Atrial fibrillation (AFib) is an abnormal rhythm from the upper two chambers of the heart, says Robert Fishel, MD, director of cardiac electrophysiology at JFK Medical Center. In this video, he describes what happens inside a heart with AFib.

Dr. Vivek Y. Reddy, MD
Cardiac Electrophysiologist

Atrial fibrillation and atrial flutter are the most common forms of arrhythmia. They are a leading cause of stroke and can lead to heart failure.

Atrial fibrillation occurs when the upper chambers of the heart, the atria, beat out of sync with the lower chambers, called the ventricles. The resulting quivering leaves blood pooled in the atria, putting patients at risk for blood clots that can cause a stroke. The ventricles often compensate by contracting more rapidly, potentially enlarging and weakening the heart.

Temporary atrial fibrillation can revert to normal on its own. If it persists, doctors sometimes treat with medications, and when this fails or is not tolerated, doctors can perform a catheter procedure (called Catheter Ablation) to eliminate the cause of the arrhythmia.

Atrial flutter is similar to atrial fibrillation, but with more regular intervals between beats.

Brigham and Women's Hospital
Administration Specialist

Atrial fibrillation (AF) describes an arrhythmia, or abnormal heart rhythm. Several conditions—including valvular heart disease, high levels of thyroid hormone, and certain forms of heart failure (weakened heart muscle)—can cause it. Some people have no apparent cause—a condition called "lone" atrial fibrillation.

Atrial fibrillation can also accompany aging, and this is one of the reasons why the prevalence of this form of abnormal heartbeat is on the rise. In atrial fibrillation, the upper chambers of the heart (the atria) wiggle ineffectively without pumping properly, and with chaotic rather than orderly contraction. This situation causes several troublesome problems.

Often, but not always, people with atrial fibrillation experience a rapid, irregular heartbeat that can be annoying or even frightening, and can also cause low blood pressure, low heart output, and faintness or fatigue.

Dr. Robert H. Levitt, MD
Cardiologist (Heart Specialist)

Atrial fibrillation (AFib) is disorder of the rhythm of the heart. Instead of your heart beating in a very regular fashion, in atrial fibrillation the heart beats very irregular. When the heart is in atrial fibrillation, it can beat very rapidly. The symptoms of atrial fibrillation can be rapid pulse, lightheadedness, shortness of breath or chest pain. Some patients experience no symptoms at all. It is estimated that 2.2 million Americans have atrial fibrillation.

Continue Learning about Atrial Fibrillation

Atrial Fibrillation

Atrial Fibrillation

Atrial fibrillation -- the most common type of cardiac arrhythmia -- causes an irregular heartbeat that can increase your risk for stroke and heart failure. Atrial fibrillation (AF or AFib) results from faulty signals produced by ...

the heart's electrical system, causing the upper portion of the heart to fibrillate, or contract rapidly and irregularly. AFib doesn't cause noticeable symptoms for everyone. For those who do experience symptoms, heart palpitations are common along with feeling weak, dizzy and tired. Learn more about atrial fibrillation with expert advice from Sharecare.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.