What is Atrial Fibrillation?

Atrial fibrillation 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.

Atrial fibrillation occurs when rapid, disorganized electrical signals cause the, the two upper chambers of the heart, to fibrillate. The term “fibrillate” means to contract very fast and irregularly.

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

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

To understand atrial fibrillation, it helps to understand the heart’s internal electrical system. The heart’s electrical system controls the rate and rhythm of the heartbeat.

With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As the signal travels, it causes the heart to contract and pump blood. The process repeats with each new heartbeat.

Each electrical signal begins in a group of cells called the sinus node or sinoatrial (SA) node. The SA node is located in the right atrium. In a healthy adult heart at rest, the SA node fires off an electrical signal to begin a new heartbeat 60 to 100 times a minute. (This rate may be slower in very fit athletes.)

From the SA node, the electrical signal travels through the right and left atria. This causes the atria to contract and pump blood into the ventricles.

The electrical signal then moves down to a group of cells called the atrioventricular (AV) node, located between the atria and the ventricles. Here, the signal slows down just a little, allowing the ventricles time to finish filling with blood.

The electrical signal then leaves the AV node and travels to the ventricles. This causes the ventricles to contract and pump blood out to the lungs and the rest of the body. The ventricles then relax, and the heartbeat process starts all over again in the SA node.

In atrial fibrillation, the heart’s electrical signals don’t begin in the SA node. Instead, they begin in another part of the atria or in the nearby pulmonary veins. The signals don’t travel normally, and they may spread throughout the atria in a rapid, disorganized way. This can cause the atria to fibrillate.

The abnormal electrical signals flood the AV node with electrical impulses. As a result, the ventricles also begin to beat very fast. However, the AV node can’t conduct the signals to the ventricles as fast as they arrive. So, even though the ventricles may be beating faster than normal, they aren’t beating as fast as the atria.

Thus, the atria and ventricles no longer beat in a coordinated way. This creates a fast and irregular heart rhythm. In atrial fibrillation, the ventricles may beat 100 to 175 times a minute, in contrast to the normal rate of 60 to 100 beats a minute.

When this happens, blood isn’t pumped into the ventricles as well as it should be. Also, the amount of blood pumped out of the ventricles to the body is based on the randomness of the atrial beats.

The body may get rapid, small amounts of blood and occasional larger amounts of blood. The amount will depend on how much blood has flowed from the atria to the ventricles with each beat.

Most of the symptoms of atrial fibrillation are related to how fast the heart is beating. If medicines or age slow the heart rate, the symptoms are minimized.

Atrial fibrillation may be brief, with symptoms that come and go and end on their own. Or, the condition may be persistent and require treatment. Sometimes atrial fibrillation is permanent, and medicines or other treatments can’t restore a normal heart rhythm.

People who have atrial fibrillation can live normal, active lives. For some people, treatment can cure atrial fibrillation and restore normal heart rhythms.

For people who have permanent atrial fibrillation, treatment can successfully control symptoms and prevent complications. Treatments include medicines, medical procedures, and lifestyle changes.
 

Paroxysmal Atrial Fibrillation
In paroxysmal atrial fibrillation, the abnormal electrical signals and rapid heart rate begin suddenly and then stop on their own. Symptoms can be mild or severe and last for seconds, minutes, hours, or days.
Persistent Atrial Fibrillation
Persistent atrial fibrillation is a condition in which the abnormal heart rhythm continues until it’s stopped with treatment.
Permanent Atrial Fibrillation
Permanent atrial fibrillation is a condition in which a normal heart rhythm can’t be restored with the usual treatments. Both paroxysmal and persistent atrial fibrillation may become more frequent and, over time, result in permanent atrial fibrillation.

Atrial fibrillation occurs when the electrical signals traveling through the heart are conducted abnormally and become very rapid and disorganized.

This is the result of damage to the heart’s electrical system. The damage most often is the result of other conditions, such as coronary heart disease or high blood pressure, that affect the health of the heart.  Sometimes, the cause of atrial fibrillation is unknown.

The risk of atrial fibrillation increases as you age. This is mostly because as you get older, your risk for heart disease and other conditions that can cause atrial fibrillation also increases. Atrial fibrillation is more common in people who have heart diseases or conditions, such as:

Atrial fibrillation also is more common in people who are having heart attacks or who have just had surgery.

Other conditions that increase atrial fibrillation risk include hyperthyroidism (too much thyroid hormone), obesity, high blood pressure, diabetes, and lung disease.

Other factors also can increase your risk of atrial fibrillation. For example, drinking large amounts of alcohol, especially binge drinking, increases your risk. Even modest amounts of alcohol can trigger atrial fibrillation in some people. Caffeine or psychological stress also may trigger atrial fibrillation in some people.

Some evidence suggests that people who have sleep apnea are at greater risk for atrial fibrillation. Sleep apnea is a common disorder in which you have one or more pauses in breathing or shallow breaths while you sleep.

Metabolic syndrome also increases your risk of atrial fibrillation. People who have this condition have a group of risk factors that increase their risk of heart disease and other health problems.

Recent research suggests that people who receive high-dose steroid therapy are at increased risk of atrial fibrillation. This therapy, which is commonly used for asthma and certain inflammatory conditions, may act as a trigger in people who already have other atrial fibrillation risk factors.

References:
1. National Heart, Lung, and Blood Institute