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JAMA PATIENT PAGE | Cardiology
Atrial Fibrillation
Atrial fibrillation is a common arrhythmia (abnormal heart rhythm).
The heart has 4 chambers: the right and left atria (upper chambers) and the right and left ventricles (lower chambers). A normal
heartbeat begins in the right atrium. The sinoatrial (SA) node is a
collection of specialized cells that initiate an electrical signal that travels through the heart muscle. This signal causes the atria to contract, which pumps blood from the atria into the ventricles. The signal travels through the atrioventricular (AV) node and into the
muscle around the ventricles. When the ventricles contract, blood
is pumped to the lungs and the rest of the body.
Heart rate is the number of times your heart beats in 1 minute.
Heart rhythm is the regularity of your heartbeat. In a normal rhythm,
heartbeats are evenly spaced.
In atrial fibrillation, the electrical signal that travels through the
heart is uncoordinated. This disorganized electrical signal starts at
a site other than the SA node and leads to a rapid and irregular heartbeat. During episodes of atrial fibrillation, blood is not pumped
through the heart efficiently. Episodes may be brief or prolonged.
Normal heart rhythm
Atrial fibrillation
Electrical activity starts in the SA node.
The atria contract, and blood empties
into the ventricles.
Right
atrium
SA node
AV node
Electrical activity in the atria is
disorganized. The atria quiver,
and blood may pool and form clots.
Left
atrium
BLOOD
FLOW
Right
ventricle
Clot
Electrical
signal
Left
ventricle
Normal rhythm
Atrial fibrillation
rhythm
Causes of Atrial Fibrillation
Diseases that affect the heart are common causes of atrial fibrillation. These include heart failure, heart valve disease, high blood pressure, and heart attack. Other causes include obesity, chronic obstructive pulmonary disease, an abnormal heart structure,
hyperthyroidism, and alcohol intoxication.
Symptoms
Some people with atrial fibrillation have symptoms such as palpitations (a fluttering sensation in the chest), shortness of breath, chest
pain, dizziness, and fatigue. Other people do not have any symptoms and might not know they have atrial fibrillation. A doctor might
identify an abnormal heart rhythm during a physical examination.
Atrial fibrillation may also be found on an electrocardiogram that is
performed for another reason.
To help the heart maintain a regular rhythm, a doctor might
prescribe an antiarrhythmic medication. A procedure called
cardioversion is the use of an electrical shock (or, less commonly,
a drug) to restore a normal rhythm. Catheter ablation involves
using small electrodes to scar the heart tissue that generates
abnormal electrical signals.
If you have atrial fibrillation, you are at increased risk of stroke.
A rapid, irregular heartbeat can cause blood to pool in the atria and
a blood clot to develop. Many patients with atrial fibrillation are prescribed an anticoagulant (a medicine that helps prevent blood clots).
Anticoagulation is especially important if you have atrial fibrillation
and you are a woman, are aged 65 years or older, or have a history
of congestive heart failure, high blood pressure, stroke or transient
ischemic attack, vascular disease, or diabetes.
Treatment
Treatment approaches are different for different people. A doctor
will consider your medical history and your symptoms before recommending a treatment plan. Goals of treatment include maintaining a normal heart rate and rhythm and preventing stroke.
For many patients, medications that control heart rate can help
maintain a normal heart rate by slowing the electrical signal as it travels through the AV node. For some patients, the best rate-control
treatment option might be ablation (destruction) of the AV node
and placement of a pacemaker.
Author: Amy E. Thompson, MD
Sources: National Heart, Lung, and Blood Institute, National Institutes of Health
Marchlinski F. The tachyarrhythmias. In: Longo DL, Fauci AS, Kasper DL, et al,
eds. Harrison’s Principles of Internal Medicine. 18th ed. New York, NY: McGrawHill; 2012:1881-1885.
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FOR MORE INFORMATION
National Heart, Lung, and Blood Institute
www.nhlbi.nih.gov/health/health-topics/topics/af
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JAMA March 10, 2015 Volume 313, Number 10 (Reprinted)
Copyright 2015 American Medical Association. All rights reserved.
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