Atrial Fibrillation

Atrial fibrillation describes an irregular and often rapid heart rhythm. The irregular rhythm, or arrhythmia, results from abnormal electrical impulses in the heart. The irregularity can be continuous, or it can come and go.

Normal heart contractions begin as an electrical impulse in the right atrium. This impulse comes from an area of the atrium called the sinoatrial (SA) or sinus node, the “natural pacemaker.”

• As the impulse travels through the atrium, it produces a wave of muscle contractions. This causes the atria to contract.
• The impulse reaches the atrioventricular (AV) node in the muscle wall between the 2 ventricles. There, it pauses, giving blood from the atria time to enter the ventricles.
• The impulse then continues into the ventricles, causing ventricular contraction that pushes the blood out of the heart, completing a single heartbeat.

In a person with a normal heart rate and rhythm the heart beats 50-100 times per minute.

• If the heart beats more than 100 times per minute, the heart rate is considered fast (tachycardia).
• If the heart beats less than 50 times per minute, the heart rate is considered slow (bradycardia).

In atrial fibrillation, multiple impulses travel through the atria at the same time.

• Instead of a coordinated contraction, the atrial contractions are irregular, disorganized, chaotic, and very rapid. The atria may contract at a rate of 400-600 per minute.
• These irregular impulses reach the AV node in rapid succession, but not all of them make it past the AV node. Therefore, the ventricles beat slower, often at rates of 110-180 beats per minute in an irregular rhythm.
• The resulting rapid, irregular heartbeat causes an irregular pulse and sometimes a sensation of fluttering in the chest.

Atrial fibrillation can occur in several different patterns.

• Intermittent (paroxysmal): The heart develops atrial fibrillation and typically converts back again spontaneously to normal (sinus) rhythm. The episodes may last anywhere from seconds to days.
• Persistent: Atrial fibrillation occurs in episodes, but the arrhythmia does not convert back to sinus rhythm spontaneously. Medical treatment is required to end the episode.
• Permanent: The heart is always in atrial fibrillation. Conversion back to sinus rhythm either is not possible or is deemed not appropriate for medical reasons.

Atrial fibrillation, often called A Fib, is a very common heart rhythm disorder.

• It affects about 1% of the population, mostly people older than 50 years. This amounts to more than 2 million people.
• The risk of developing atrial fibrillation increases as we get older. About 5% of people older than 80 years have atrial fibrillation.

For many people, atrial fibrillation may cause symptoms but does no harm.

• Complications can arise, but appropriate treatment reduces these risks.
• If treated properly, atrial fibrillation rarely causes serious or life-threatening problems.

Atrial Fibrillation Causes

Atrial fibrillation may occur without evidence of underlying heart disease. This is more common in younger people, about half of whom have no other heart problems. This is often called lone atrial fibrillation. Some of the causes not involving the heart include the following:

• Hyperthyroidism (overactive thyroid)
• Alcohol use (holiday heart)
• Pulmonary embolism (a blood clot in the lungs)
• Pneumonia

Most commonly, atrial fibrillation occurs as a result of some other cardiac condition (secondary atrial fibrillation).

• Heart valve disease: This can be something you are born with or be caused by infection or degeneration/calcification of valves with age.
• Enlargement of the left ventricle walls (left ventricular hypertrophy)
• Coronary heart disease (or coronary artery disease): This results from atherosclerosis, deposits of fatty material inside the arteries that cause blockage or narrowing of the arteries.
• High blood pressure (hypertension)
• Cardiomyopathy (disease of the heart muscle) leading to congestive heart failure
• Sick sinus syndrome (improper production of electrical impulses because of malfunction of the SA node)
• Pericarditis (inflammation of the sac surrounding the heart)

Atrial fibrillation frequently occurs after cardiothoracic (open heart) surgery, but often resolves in a few days.

For many people with infrequent and brief episodes of atrial fibrillation, the episodes are brought on by a number of triggers. Because some of these involve excessive alcohol intake, this is sometimes called holiday heart. Some of these people are able to avoid episodes or have fewer episodes by avoiding their trigger. Common triggers include alcohol and caffeine in susceptible individuals.

Atrial Fibrillation Symptoms

Symptoms of atrial fibrillation vary from person to person.

• A number of people have no symptoms.
• The most common symptom in people with intermittent atrial fibrillation is palpitations, a sensation of rapid or irregular heartbeat. This may make some people very anxious. Many people also describe an irregular fluttering sensation in their chests.
• Some become light-headed or faint.
• Other symptoms include weakness, lack of energy or shortness of breath with effort, and chest pain.