What is atrial fibrillation?
Atrial fibrillation, or AFib, is
the most common type abnormal heart rhythm (arrhythmia). Normally, a specific group of
cells begins the signal to start your heartbeat. These cells are in the sinoatrial (SA)
node. This node is in the right atrium, the upper right chamber of the heart. The signal
quickly travels down the heart’s conducting system. It travels to the upper-left filling
chamber of the heart (left atrium) and to the left and right ventricle, the 2 lower
pumping chambers of the heart. As it travels, the signal triggers the chambers of the
heart to contract. The atria contract with each heartbeat to move blood into the
During AFib, the signal to start
the heartbeat is disorganized. This causes the atria to quiver (fibrillate). The
disorganized signals are then transmitted to the ventricles. It causes them to contract
irregularly and sometimes quickly. The contraction of the atria and the ventricles is no
longer coordinated. The amount of blood pumped out to the body will vary with each
heartbeat. The ventricles may not be able to pump blood efficiently to the body.
The quivering atria can lead to
blood pooling. This pooling can cause blood clots to form inside the heart. Most clots
form inside the left atrium. That’s because the left atrium has a pouch (left atrial
appendage) in the muscle wall. This pouch is often large with several lobes. Blood can
pool and form clots inside the lobes. This increases the risk of forming blood clots.
These clots can then be pumped out of the heart and travel to the brain, causing a
stroke. This is why AFib greatly increases the risk for stroke.
Doctors don’t fully know the function of this pouch.
Doctors classify AFib in 3 ways:
Parosyxmal. Sometimes AFib occurs briefly and then goes away on its own. It
may last for seconds, minutes, hours, or up to 7 days before returning to a normal
Persistent. This is AFib that does not go away on its own. Treatment may be
used to return the heart to normal rhythm. It lasts for 7 days or longer. AFib that
lasts longer than a year is called long-standing persistent atrial fibrillation.
Permanent. Afib may be called permanent when a decision is made to no longer
control the heart’s rhythm or despite best efforts, normal rhythm can’t be
AFib is common in adults. The risk
increases with age. It is more common in men than in women.
What causes atrial fibrillation?
AFib can happen from any type of problem that changes the way the heart handles electricity. Sometimes the cause is unknown. There is a range of things that can increase this risk. Some of the risks include:
- Older age
- High blood pressure
- Coronary artery disease
- Heart failure
- Rheumatic heart disease from a past
- Heart valve defects such as mitral
valve prolapse with regurgitation
- Congenital heart defects
- Sick sinus syndrome
- Lung disease
- Obstructive sleep apnea
- Metabolic syndrome
- High-dose steroid therapy
AFib is also more likely to happen
during an infection or right after surgery. Stress, caffeine, and alcohol may also set
off attacks. People who do a lot of repeated vigorous endurance exercises, such as
running marathons, can develop atrial fibrillation.
Certain people may be at greater
risk of developing AFib. This is because of differences in genes they inherited from
their parents. This is not yet fully understood.
Who is at risk for atrial fibrillation?
AF is more common in people who are
over 65. It’s also more common in men than women. Underlying heart disease, high blood
pressure, thyroid problems, too much alcohol use, sleep apnea, and certain lung disease
put people at risk for atrial fibrillation.
What are the symptoms of atrial fibrillation?
AFib can cause different symptoms. This is especially true when it is not treated. These can include:
- The feeling that your heart is
skipping beats or beating too hard (heart palpitations)
- Shortness of breath
- Chest pain
- Dizziness or fainting
- Weakness and tiredness (fatigue)
- Swelling in the feet, ankles, and legs
Sometimes AFib has no symptoms. The
first symptom of atrial fibrillation may be symptoms of a stroke.
How is atrial fibrillation diagnosed?
Diagnosis starts with a health
history and physical exam. An internist or primary care healthcare provider will often
makes the diagnosis. You may be sent to a cardiologist for more assessment and
An electrocardiogram (ECG) is very
important for a diagnosis. Healthcare providers use this test to study the heart signal
and rhythm. In some cases, the diagnosis can be made based on this test alone. If the
AFib comes and goes, you might need an electrocardiogram over a longer period with a
Holter monitor or an event recorder to pick up the rhythm. Sometimes you may have a
small implanted heart recording device called implantable loop recorders put under the
skin over the heart. This can monitor for AFib over several years.
Other tests might be used to help plan treatment. These might include:
- Echocardiogram, to check the hearts
structure and function
- Cardiac stress testing, to check the
blood flow in the heart
- Blood work, to check for thyroid
levels, diabetes, and possible health conditions
- Sleep study, when obstructive sleep apnea is suspected