Atrial Fibrillation

Overview

Atrial fibrillation (AF) is a fast, irregular heart rhythm in which the two upper chambers of the heart (the atria) quiver rapidly (fibrillate) instead of pumping at a normal steady pace.

Types of AF

  1. Paroxysmal atrial fibrillation. Paroxysmal AF is an intermittent form of AF that comes and goes on its own.
  2. Persistent atrial fibrillation. Persistent AF is a longer lasting type of AF, which can be corrected with treatment.
  3. Permanent atrial fibrillation. Permanent AF does not go away and cannot be stopped with treatment.

Heart functions

The heart’s natural pacemaker, the sinoatrial node (SA node), is a collection of tiny cells that send electrical signals to produce heartbeats. Normally, the SA node generates electrical signals that trigger well-timed, organized contractions of the upper chambers (atria) and the lower chambers (ventricles). However, in AF, the electrical signals are fast and chaotic. The atria quiver rapidly and irregularly, so blood pools in the atria instead of being pumped properly to the ventricles. In some patients with AF, the ventricles also pump poorly in a condition known as heart failure.

Causes

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Atrial fibrillation

Underlying heart disease is by far the most common cause of AF. Numerous conditions leading to AF include the following:

Symptoms

During atrial fibrillation, some people do not experience any symptoms at all. Other individuals are affected by symptoms ranging from mild to severe. Symptoms include:

  • Feeling a fast heartbeat or fluttering in the chest (palpitations)
  • Lightheadedness or dizziness
  • Weakness 
  • Fatigue 
  • Shortness of breath
  • Anxiety
  • Chest pain.

Complications

  • Blood clot. In atrial fibrillation, blood pools in the heart and increases the risk of clot formation. A blood clot in the heart is extremely dangerous because it may break free, travel through blood vessels, and lodge itself the brain where it causes a stroke.
  • Stroke. Individuals with atrial fibrillation have a significantly increased risk of a stroke from blood clot formation in the heart. Stroke occurs when blood flow to an area of the brain is markedly decreased. This lack of blood and oxygen results in brain damage that may permanently impair a person’s bodily functions.
  • Heart failure. In atrial fibrillation, the ventricles may pump poorly and fail to deliver blood to the body. This debilitating condition, termed heart failure, leads to deteriorating symptoms.

Diagnosis

Usually a physical exam will reveal irregular heart sounds and an abnormal pulse rate. When atrial fibrillation is suspected, further testing is required to confirm the diagnosis.

  • Electrocardiogram (ECG). An ECG is a test that provides a recording of the heart’s electrical activity.
  • Holter monitor. A Holter monitor is an external device worn continuously that records the heart's electrical activity for 24 to 48 hours.
  • Cardiac event recorder. While experiencing an episode of symptoms, a patient activates a portable cardiac event recorder, which monitors and records the electrical activity of the heart. The patient uses the device to transmit the data promptly over the phone to a doctor for analysis.

Treatment

Some people with AF spontaneously convert back to a normal rhythm without treatment. In other cases, some form of treatment is required. The specific treatment depends on how long an individual has been in AF and the severity of symptoms.

The primary goals of AF treatment include the following:

  1. Restore a normal heart rhythm
  2. Slow the heart rate while a patient remains in AF
  3. Prevent blood clot formation and decrease the risk for stroke
  4. Decrease the risk for heart failure.

Medications

  • Antiarrhythmic medications are used to restore a normal heart rhythm completely. These drugs are not always effective, so alternative treatments may be necessary.
  • Medications mainly used for the purpose of slowing the heart rate include beta-blockers and calcium channel blockers. These medications do not cure the condition. The atrial fibrillation persists but at a much slower rate, so a person’s symptoms are under control.
  • Blood-thinning medication is essential for permanent AF to reduce blood clot formation and the risk of stroke.
  • When an overactive thyroid (hyperthyroidism) is the cause of AF, anti-thyroid medications that treat the thyroid condition usually restore a normal heart rhythm.

Other Treatments

  • Cardioversion. An electrical shock is delivered to the heart to reset the rhythm back to normal.
  • Catheter ablation. Catheters are passed through blood vessels into the heart to heat or freeze (ablate) abnormal electrical pathways.
  • Maze procedure. A Maze procedure is a type of surgery in which abnormal electrical pathways in the heart are destroyed.

Prevention

AF is often a consequence of underlying heart problems; therefore, measures that prevent heart disease also reduce the risk of AF. Lifestyle factors like a healthy diet, regular exercise, quitting smoking, and avoiding alcohol abuse are recommended.

Sources

  • Atrial Fibrillation. American Heart Association website. http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Atrial-Fibrillation-AF-or-AFib_UCM_302027_Article.jsp. Accessed April 22, 2015.
  • Atrial Fibrillation. UCLA Health website. http://healthinfo.uclahealth.org/Search/85,P00198. Accessed April 22, 2015. 
  • Atrial Fibrillation. Cleveland Clinic website. http://my.clevelandclinic.org/services/heart/disorders/arrhythmia/afib. Accessed April 22, 2015.
  • Atrial fibrillation. Mayo Clinic website. http://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/basics/definition/con-20027014. Accessed April 22, 2015.
  • What is Atrial Fibrillation. National Heart, Lung, and Blood Institute website. http://www.nhlbi.nih.gov/health/health-topics/topics/af. Accessed April 23, 2015.