Atrial Fibrillation

What is atrial fibrillation?

Atrial fibrillation is the most common cardiac arrhythmia, or abnormal heart rhythm seen today. Approximately 2.2 million Americans suffer from this disorder. On average, there are 160,000 new cases of atrial fibrillation per year.

Atrial fibrillation is a disorder that involves the upper two chambers of the heart (atria) where they no longer beat in a normal, synchronized fashion. Rather, electrical impulses move about both atria in a chaotic, or circus-movement pattern, resulting in activation of the atria somewhere between 400 and 600 times per minute. The hallmark sign of atrial fibrillation is an irregularly irregular rhythm where the ventricles, or bottom pumping chambers of the heart, beat in a very chaotic fashion.

ATRIAL FIBRILLATION

NORMAL SINUS RHYTHM (normal EKG)

What are the symptoms of atrial fibrillation?

Many patients with atrial fibrillation have no symptoms and are unaware of the abnormal heart rhythm. The most common symptom of atrial fibrillation is palpitations, an uncomfortable awareness of the rapid and irregular heartbeat. Other symptoms of atrial fibrillation are caused by the diminished delivery of blood to the body. These symptoms include dizziness, fainting, weakness, fatigue, shortness of breath, and angina (chest pain due to reduced blood flow to the heart muscles).

When a blood clot dislodges from the atria and embolizes to the brain, a sudden onset of paralysis (embolic stroke) can occur. A blood clot, which embolizes to the lungs, can cause injury to the lung tissues (pulmonary infarction), with resulting symptoms of chest pain and shortness of breath. When blood clots travel to and lodge in the body's extremities, a sudden onset of cold arms, feet, or legs occurs.

A major risk of atrial fibrillation is stroke, with the incidence of stroke approximately five times that of similar-aged individuals who do not have atrial fibrillation. The risk factors which appear to increase the risk of stroke in individuals with atrial fibrillation include age greater than 65 years, presence of diabetes mellitus, presence of hypertensive heart disease, congestive heart failure, mitral stenosis (tight mitral valve), or history of prior stroke or near-stroke (Transient Ischemic Attack). The risk of stroke in individuals with atrial fibrillation may be significantly reduced by use of anticoagulant therapy in the form of Warfarin (coumadin).

What are the risk factors for developing atrial fibrillation?

Risk factors for developing atrial fibrillation include:

• Increased age (1% of people over 60 years old have atrial fibrillation)
• Coronary heart disease (including heart attack)
• High blood pressure
• Abnormal heart muscle function (including congestive heart failure)
• Mitral valve disease (including mitral valve prolapse)
• Overactive thyroid, or overdose of thyroid medication
• Low amounts of oxygen in the blood (for example, as occurs with lung diseases such as emphysema or chronic obstructive pulmonary disease (COPD)
• Inflammation of the lining surrounding the heart (pericarditis)
• Blood clots in the lung (pulmonary embolism)
• Chronic lung diseases (emphysema, asthma, COPD)
• Alcohol abuse
• Stimulant drug use (cocaine or decongestants)
• Recent heart or lung surgery
• Abnormal heart structure from the time of birth (congenital heart disease).

About 1 in 10,000 otherwise healthy, young adults have atrial fibrillation without any apparent cause or underlying heart disease. Atrial fibrillation in these individuals is usually intermittent, but can become chronic in 25% of those affected. This condition is referred to as lone atrial fibrillation. Stress and alcohol and tobacco use may play a role in causing atrial fibrillation.

What are the treatment options for atrial fibrillation?

The treatment of atrial fibrillation is a highly individual matter. Your doctor will take a thorough history and perform a thorough physical examination to determine if your atrial fibrillation is due to another problem, such as hypertension, coronary artery disease, valvular heart disease, or thyroid dysfunction. Often, these primary problems may be treated, with resolution of the atrial fibrillation. If the atrial fibrillation is not corrected by resolution of the primary problem, other treatment options may be used.

The goals of atrial fibrillation treatment include: 1) slowing the rapid heart rate (the rate of ventricular contractions); 2) preventing blood clot embolization and strokes; and 3) converting the irregular rhythm back to normal rhythm whenever possible. Converting atrial fibrillation back to a normal heart rhythm can be accomplished with medications (a process called chemical cardioversion) or by electrical shocks (a process called electrical cardioversion).

Mediation are necessary in some cases to slow down signal transmission though the AV node in order to modulate the rapid heart rate. Medications to slow the heart rate in atrial fibrillation include:

• Digitalis (Digoxin)
• Beta blockers - such as Propranolol (Inderal), Atenolol (Tenormin), Metroprolol (Lopressor), etc.
• Calcium channel blockers - Verapamil (Calan), Diltiazem (Cardizem)

All of these medications slow the heart rate by delaying atrial signal transmissions through the AV node. These medications, however, do not generally convert atrial fibrillation back to normal heart rhythm. Other drugs or treatments are necessary to achieve a normal heart rhythm.
Some elderly patients have slow signal transmissions through their AV nodes due to diseases within the AV nodes. When these patients develop atrial fibrillation, their hearts beat irregularly, but the heart rate remains normal or slower than normal without any medications. As their disease in the AV node advances, these patients can even develop an excessively slow heart rate and require a permanent pacemaker to increase the rate of ventricular contractions.

Once the rate of ventricular contractions is under control, conversion of atrial fibrillation to normal heart rhythm is usually attempted in order to improve the efficiency of the heart and to decrease the risk of stroke. Some patients, however, fail these conversion attempts or develop recurrent atrial fibrillation. For these patients, the decision may be made to leave them in atrial fibrillation, control their rapid heart rate, and maintain them on blood thinners (Coumadin or Aspirin) to avoid strokes.