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What Is Atrial Fibrillation? AFib Causes and Symptoms

Updated on September 15, 2021
Article written by
Emily Wagner, M.S.

  • Atrial fibrillation is a heart condition in which the heart’s upper chambers (atria) beat irregularly and out of sync with its lower chambers.
  • Atrial fibrillation is the most common type of heart arrhythmia (irregular heartbeat) treated in the United States.
  • Symptoms of atrial fibrillation include heart palpitations, fatigue, shortness of breath, and sweating.

Atrial fibrillation, or AFib, is a heart condition in which the upper chambers of the heart (known as the atria) beat irregularly. Afib is known as an arrhythmia, an abnormal heartbeat — which can be slower or faster than usual. In AFib, because the upper and lower chambers of the heart are not working together, the efficiency of the heart’s contractions decreases.

AFib is the most common heart rhythm disorder treated in the United States. The Centers for Disease Control and Prevention (CDC) estimate 12.1 million people will have AFib in the U.S. by 2030. Women and people of European descent are more likely to experience AFib.

Causes of Atrial Fibrillation

In a healthy, functioning heart, all four chambers beat together in a normal rhythm. This is controlled by a group of cells in the upper right chamber of the heart known as the sinus node. The sinus node acts as the heart’s natural pacemaker, and it uses electrical signals to start each heartbeat.

During AFib, the electrical signals in the atria are chaotic, causing the heart to beat (quiver) in an irregular rhythm. This means the atria cannot pump enough blood to the ventricles, which can lead to a number of health problems. The normal range for a heart rate is 60 to 100 beats per minute (bpm). However, in AFib, the heart rate is increased to 100 to 175 bpm.

The most common causes of AFib are abnormalities or damage to the heart muscles and structure. These causes can include:

  • Abnormal heart valves
  • High blood pressure (hypertension)
  • Coronary artery disease
  • Improper functioning of the sinus node (sick sinus syndrome)
  • An overactive thyroid gland (hyperthyroidism)
  • Congenital (present since birth) heart defects
  • A previous heart surgery
  • Lung diseases
  • Viral infections
  • Sleep apnea
  • Stress due to pneumonia, surgery, or other health conditions

Risk Factors for AFib

Certain factors can put you at a higher risk for developing AFib. These include:

  • Older age
  • Family history
  • High blood pressure
  • Smoking
  • Diabetes
  • Obesity
  • Chronic kidney disease
  • European ancestry
  • Heart failure
  • Ischemic heart disease
  • Moderate to heavy alcohol consumption
  • Hyperthyroidism
  • Enlarged chambers on the heart’s left side

Symptoms of Atrial Fibrillation

In some cases, a person with AFib may not know they have the condition because they may not have any symptoms. Others can experience symptoms, including:

  • Rapid and irregular heartbeat
  • Fatigue, especially when exercising
  • Dizziness
  • Thumping or fluttering in the chest (heart palpitations)
  • Weakness
  • Sweating
  • Shortness of breath
  • Anxiety
  • Confusion
  • Chest pain or pressure (This is a medical emergency. If this occurs, call 911 or seek medical attention immediately.)

If you don’t have any of the above symptoms, AFib may be detected during a physical examination where a doctor listens to your heart, such as a routine physical or an appointment for another reason. “I was so surprised, up until this time I felt fine,” a MyHeartDiseaseTeam member commented. “I was admitted into the hospital for something else. They told me there I had Afib.”

If your doctor notices an unusual heartbeat, they may refer you to a cardiologist for further evaluation. A cardiologist may order a number of tests, including an electrocardiogram, an echocardiogram, and blood tests, to diagnose AFib.

There are four main types of AFib: paroxysmal AFib, persistent AFib, long-term persistent AFib, and permanent AFib. Each type is defined by how long AFib symptoms last and their severity.

Symptoms of Heart Attack and Stroke

Many of the symptoms of AFib overlap with other, more serious conditions such as heart attack or stroke. In fact, having AFib means you are nearly five times more likely to have a stroke than someone without AFib. This is because blood clots can develop during AFib. These blood clots can subsequently break off into the bloodstream and become stuck in an artery leading to the brain.

Because individuals with AFib have an increased risk for heart attack and stroke, it is important to know the signs and symptoms of both conditions.

Symptoms of a heart attack include:

  • Discomfort (pressure, squeezing, pain) in the middle of the chest that lasts for a few minutes or more, or comes and goes
  • Discomfort in one or both arms, neck, jaw, stomach, or back
  • Cold sweats
  • Nausea
  • Shortness of breath
  • Lightheadedness

The acronym FAST can help you remember the warning signs of a stroke:

  • Face drooping — One side of the face will droop or become numb.
  • Arm weakness — One arm may become numb or weak.
  • Speech difficulty — Speech will be slurred or difficult to understand, or speech may become impossible.
  • Time to call 911 — If any of these warning signs occur, even if they go away, call 911 or emergency services immediately.

There are steps you can take to reduce your risk of heart attack and your risk of stroke, including taking certain medications and making lifestyle changes.

Treating AFib

Treatments for atrial AFib focus on resetting the heart’s rhythm, controlling the heart rate, and preventing blood clots. Treatment options for AFib include cardioversion, a procedure to reset the heart rhythm; surgery; and medications like anticoagulants (blood thinners) and anti-arrhythmic drugs. Lifestyle changes like exercise can also help manage AFib and your overall heart health.

Read more about treatments and medications for atrial fibrillation here.

Talk With Others Who Understand

MyHeartDiseaseTeam is the social network for people with heart disease and their loved ones. More than 51,000 members come together to ask questions, give advice, and share their stories with others who understand life with heart disease.

Do you have AFib? Share your experience in the comments below, or start a conversation by posting on MyHeartDiseaseTeam.

All updates must be accompanied by text or a picture.
Larry A. Weinrauch, MD, FACC, FACP, FAHA is an assistant professor of medicine at Harvard Medical School with a focus on cardiovascular disease and clinical outcomes research. Review provided by VeriMed Healthcare Network. Learn more about him here.
Emily Wagner, M.S. holds a Master of Science in biomedical sciences with a focus in pharmacology. She is passionate about immunology, cancer biology, and molecular biology. Learn more about her here.

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