Atrial fibrillation

Abnormal heart rhythm

Basic Information


Atrium, Atrial fibrillation Atrial fibrillation is an abnormal heart rhythm (arrhythmia) in which the upper chambers of the heart (atria) beat irregularly (and usually ineffectively) and very rapidly (up to 500 beats per minute). Not all of these beats pass through the impulse carrier (atrioventricular node) between the atria and the ventricles (lower chambers of the heart). Therefore, the ventricular rate is also rapid but very irregular (80 to 160 beats per minute). Atrial fibrillation is the most common arrhythmia found in heart disorders. The inefficient pumping action of the heart in atrial fibrillation reduces the output of blood into the circulation. Blood clots in the atria can enter the bloodstream and become lodged in an artery (embolism). This is particularly serious when if affects the main artery leading to the brain (stroke).

Atrial fibrillation occurs in about twenty percent of heart attacks. It also occurs with rheumatic heart disease, cardiomyopathy (disease of the heart muscle), pericarditis (inflammation of the membrane covering the heart), mitral valve prolapse (slight deformity of a heart valve causing it to leak), hypertension (high blood pressure), hyperthyroidism (overactive thyroid), thyrotoxicosis (toxic condition resulting from hyperthyroidism), pneumonia, atherosclerotic heart disease, and congenital heart disease (atrial septal defect). Atrial fibrillation may also occur in otherwise healthy adults after excessive alcohol, nicotine, or caffeine consumption, which is known as "holiday heart." It can also be associated with stress, fatigue, surgery, or as a reaction to certain prescription drugs. Though it is primarily diagnosed in individuals over age 70, it is frequently found in individuals aged 40 to 70 years. It is also found in individuals with no obvious heart disease or likely precipitating cause (lone atrial fibrillation).

Atrial fibrillation signs and symptoms

  • No symptoms (sometimes).
  • Continuously irregular heartbeat, in which no 2 beats are of equal strength or duration.
  • Weakness, dizziness or faintness (sometimes).


  • Rheumatic heart disease caused by rheumatic fever.
  • Atherosclerosis of coronary arteries, with or without a previous heart attack.
  • Hyperthyroidism.
  • Congestive heart failure.

Risk increases with

  • Stress.
  • Heart valve disease; recent heart surgery.
  • Electrolyte disturbances, especially low potassium.
  • Pulmonary embolism.
  • Excessive use of some drugs, such as thyroid hormones, caffeine and others.
  • Smoking.
  • Excess alcohol consumption.
  • Obesity.

Preventive measures

  • Don't smoke.
  • Follow suggestions under Diet. Children and young adults of parents with this condition may benefit from a low-fat diet.
  • Exercise regularly.
  • Reduce stress to a manageable level when possible.
  • If you have diabetes or high blood pressure, adhere strictly to your treatment program.

Expected outcomes

The outlook is good for individuals who experience atrial fibrillation as a one-time or intermittent occurrence or in conjunction with a heart attack. The individual may require several weeks of follow-up drug therapy because it often takes four to six weeks after defibrillation before atrial function returns to normal. For those who require emergency defibrillation, one-third will have a recurrence within a week, and the remaining two-thirds within a year. Most individuals with chronic or persistent fibrillation do well with drug therapy although their need for it may be life long.

Possible complications


General measures

  • Diagnostic tests include ECG (electrocardiogram that measures electrical activity of the heart) and blood studies to measure levels of drugs used in treatment.
  • Hospitalization (sometimes).
  • Electric shock (electrocardioversion), which may restore normal rhythm.
  • Have family members and friends learn cardiopulmonary resuscitation (CPR) in case you have cardiac arrest.
  • Don't smoke, use mind-altering drugs or drink more than 1 or 2 alcoholic drinks, if any, a day.
  • Learn to check your own pulse for rate (beats per minute), rhythm (regular or irregular) and strength. Call the doctor if these change.
  • Minimize stress.
  • Avoid non-prescription decongestants.
  • Additional information available from the American Heart Association


  • Heart medications, such as digitalis, quinidine, calcium-channel blockers or beta-adrenergic blockers to regulate the heartbeat.
  • Anticoagulants to prevent blood clot.

Coumadin (Warfarin), Tenormin (Atenolol), Cardizem (Diltiazem), Inderal (Propranolol), Isoptin Sr (Verapamil),


  • Resume your normal activities as soon as symptoms improve.
  • A regular exercise program is recommended.


  • Lose weight if you are obese, but don't use appetite suppressants. These may worsen rhythm disturbances.
  • The underlying heart condition may require a low-salt or low-fat diet and potassium supplements.


Atrial fibrillation can be a warning sign of other heart conditions such as mitral stenosis (Wolff-Parkinson-White syndrome) or thyrotoxicosis (a toxic thyroid condition). Differential diagnoses of atrial fibrillation include atrial flutter with block, shifting pacemaker associated with multifocal atrial ectopic beats, and paroxysmal atrial tachycardia. Differential diagnoses of atrial flutter include paroxysmal atrial tachycardia with variable block, ventricular tachycardia, and atrial fibrillation with block.

Notify your physician if

  • You or a family member has symptoms of atrial fibrillation.
  • The following occur during treatment:
    • Change in heart rate, rhythm or strength.
    • Chest pain, sweating and weakness.
    • Shortness of breath and swollen feet and ankles.
    • Pain in the calf of the leg while walking.
  • New, unexplained symptoms develop. Drugs used in treatment may produce side effects.

Last updated 8 August 2015


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