Atrial Fibrillation

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Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention | Organizations

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Definition

Atrial fibrillation is an abnormal heart rhythm. The heart's electrical system normally sends regularly spaced, predictable signals, telling the heart muscle to contract, or beat.

The heart has two upper chambers, called atria, and two lower chambers, called ventricles. Each signal starts in the atria and travels to the rest of the heart. In atrial fibrillation, the electrical signals from the atria are fast and irregular. The atria quiver, rather than contract. Some signals do not reach the ventricles and the ventricles continue pumping, usually irregularly and rapidly. This fast, uncoordinated rhythm prevents the heart from pumping all the blood out to the body. Blood left in the heart chambers can form clots. These clots may sometimes break away, travel to the brain and cause a stroke.

Causes

In most cases, atrial fibrillation is due to an existing heart condition. But atrial fibrillation can occur in people with no structural heart problems. A thyroid disorder or other condition may cause the abnormal rhythm. In some cases, the cause is unknown.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

• Cardiovascular diseases:
  • High blood pressure
  • Coronary artery disease
  • Congestive heart failure
  • Heart attack
  • Heart valve disease
  • Endocarditis (infection of a heart valve)
  • Cardiomyopathy (disease of the heart muscle)
  • Congenital heart disease
  • Prior episode of atrial fibrillation
• Lung diseases:
  • Emphysema
  • Asthma
  • Blood clots in the lungs
• Age: 55 or older
• Smoking
• Chronic medical conditions:
  • Overactive thyroid
  • Diabetes
• Excessive alcohol intake
• Use of stimulant drugs, including caffeine
• Sex: Male
• Surgery
• Stress, either emotional or physical

Symptoms

Symptoms can vary from mild to severe, depending on your heart function and overall health. Some people may not notice any symptoms.

Symptoms include:

• Irregular or rapid pulse or heart beat
• Racing feeling in the chest
• Palpitations, or a pounding feeling in the chest
• Dizziness, lightheadedness, or fainting
• Sweating
• Pain or pressure in the chest
• Shortness of breath
• Fatigue or weakness
• Exercise intolerance

Diagnosis

The doctor will:

• Ask about your symptoms and medical history
• Perform a physical exam
• Listen to your heart

Tests may include:

Electrocardiogram (ECG, EKG) – a test that records the heart's activity by measuring electrical currents through the heart muscle

24-hour Holter Monitoring – wearing a heart monitor that records the heart rhythm for 24-hours

Echocardiogram – a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart

Chest X-rays – to look for underlying conditions

Blood Tests – to look for underlying conditions

Treatment

The goals of treatment are to:

• Restore a regular rhythm, if possible
• Keep heart rate as close to normal as possible
• Prevent blood clots from forming

If an underlying cause of atrial fibrillation is found, it may be treated. Some patients return to a normal rhythm without treatment.

Treatments include:

Medication

Drugs to slow and regulate heart rate such as:

• Digitalis
• Verapamil
• Diltiazem
• Propranolol
• Quinidine
• Procainamide
• Other antiarrhythmic drugs

Drugs to prevent clot formation, called anticoagulants or blood thinners, such as:

• Aspirin
• Warfarin

Cardioversion

Cardioversion is a procedure that uses an electrical current or drugs to help normalize the heart rhythm. If atrial fibrillation has lasted 48 hours or more, you may be given blood thinners before this procedure.

Lifestyle Changes

Avoid caffeine and other stimulants, because they may trigger another episode. Alcohol may also act as a trigger in some people.

Prevention

If you have risk factors for atrial fibrillation, avoid known triggers, such as alcohol and caffeine. Follow your doctor's advice for controlling heart disease, high blood pressure, and other conditions.

Organizations

American Heart Association
http://www.americanheart.org/

SOURCES:

AHA Medical/Scientific Statement: "Management of Patients With Atrial Fibrillation." American Heart Association, 1996.

Griffith's 5-Minute Clinical Consult, 2001 ed. Lippincott Williams & Wilkins, 2001.

Harrison's Principles of Internal Medicine, 14th ed. The McGraw-Hill Companies, 2000.

Practice of Geriatrics, 3rd ed. W.B. Saunders Company, 1998.

Conn's Current Therapy 2001, 53rd ed. W.B. Saunders Company, 2001.

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Last reviewed September 2001 by Medical Review Board