General Facts About Heart Rhythm Disorders

• Atrial fibrillation is the most common sustained heart rhythm disorder and increases the risk for heart disease and stroke, both leading causes of death in the United States. An estimated 2.2 million adults in the United States have been diagnosed with atrial fibrillation.¹
• In 1999, a total of 66,875 deaths with A Fib as the contributing cause occurred, resulting in an age-adjusted death rate of 24.7 per 100,000 population. Of these deaths, 56,138 (84.0%) were among persons age 75 and older.²
  • The greatest proportion of these A Fib-related deaths occurred among persons age 85 or older (47.4%), followed by those aged 75-84 years (36.6%), aged 65-74 years (12.3%), and aged <65 years (3.7%).³
  • Age-adjusted death rates for A Fib were highest among whites (25.7%) and African Americans (16.4%) and higher for men (34.7%) than women (22.8%).⁴
  • The most common underlying causes of death for those who had A Fib, were coronary heart disease (28.0%), A Fib (12.4%), and stroke (10.8%).⁵
• In 1999, a total of 1,765,304 hospitalizations (137.1 per 1,000 Medicare enrollees) were reported among persons with A Fib in the Medicare population. Rates increased among successive age groups.⁶
  • The rate of hospitalization among persons with A Fib was higher among whites (142.7) than among African Americans (100.4). Although 55.7% of these hospitalizations were among women, men (162.9) had a higher rate of A Fib-related hospitalization than women (121.2).⁷
  • The most common diseases listed as the primary diagnosis for persons hospitalized with A Fib were congestive heart failure (11.8%), followed by AF (10.9%), coronary heart disease (9.9%), and stroke (4.9%).⁸

Heart Rhythm Disorders Overview

Heart rhythm disorders (arrhythmias) are problems that affect the electrical system, or "wiring," of the heart muscle. Heart arrhythmias are very common and nearly everyone will experience an abnormal heart rhythm some time during their lives. Most are not serious.

Arrhythmias can be categorized in three main ways: the rate (too slow or too fast); the location (ventricles-lower chambers of heart or atria-upper chambers); and the beat (steady or chaotic and irregular).

Types of Heart Rhythm Disorders

• Bradycardia describes a heartbeat that is too slow (less than 60 beats per minute). A normal heart contracts about 100,000 times each day, at a rate of 60 to 100 times a minute. The weak pace may mean the heart doesn't beat often enough to ensure blood flow. Slow heart rates can be the result of certain medications, congenital heart disease, or the degenerative processes of aging. Heart block (or AV Block) and Sick Sinus Syndrome are forms of bradycardia.
• Tachycardia (tachy=fast) is a too-rapid heartbeat. There are two predominant types of tachycardia: supraventricular tachycardia (SVT) and ventricular tachycardia (VT). The most common type of SVT is atrial fibrillation, an irregular and rapid heartbeat in the upper chambers of the heart (or atria). More than two million people in the United States have atrial fibrillation and 160,000 new cases are diagnosed each year. At times, ventricular tachycardia (VT) can change without warning into a deadly arrhythmia called ventricular fibrillation (VF). Suddenly rapid, irregular and chaotic heartbeats in the lower chambers of the heart (or ventricles) may be a sign of ventricular fibrillation. It is the number one cause of sudden cardiac arrest (SCA). Within seconds, an individual loses consciousness and, without immediate emergency treatment, will die within minutes. SCA is a leading cause of death in the United States, claiming more than 250,000 lives per year (cardiovascular disease is the leading cause of death in the U.S. and most deaths from cardiovascular disease are attributable to SCA).
• Premature heartbeat occurs when the heart's regular rhythm is interrupted by early or premature beats. It may feel as if the heart has skipped a beat. Usually it is not serious. If the beat arises from locations in the atria (upper chambers), it is called premature atrial beat. Premature ventricular beats (also called premature ventricular contractions or PVCs) arise from the ventricles (lower chambers).
• Fibrillation describes a heartbeat that is chaotic, or irregular, and may seem to skip beats or beat out of rhythm. This occurs when a chamber of the heart goes into spasm and fails to pump. There are two types of fibrillation: atrial fibrillation and ventricular fibrillation (see tachycardia above).

Treatment Options

The underlying cause of an arrhythmia provides the basis for selecting the best treatment. Treatments fall into several main categories along a continuum from the least to most invasive. In general, the least invasive treatment that effectively controls the arrhythmia is the treatment of choice. Options include:

• Lifestyle Changes — Since other heart disorders increase the risk of developing arrhythmias, lifestyle changes often are recommended. In addition, improving health can lesson the symptoms of arrhythmias and other heart disorders as well as prove beneficial to overall patient health.
• Medications — Medications can control abnormal heart rhythms or treat related conditions such as high blood pressure, coronary artery disease, heart failure, and heart attack. Drugs also may be administered to reduce the risk of blood clots in patients with certain types of arrhythmias.
• Cardiac Ablation — In this procedure, one or more flexible, thin tubes (catheters) are guided via x-ray into the blood vessels and directed to the heart muscle. A burst of radiofrequency energy destroys very small areas of tissue that give rise to abnormal electrical signals.
• Electronic Devices — By delivering a controlled electric shock to the heart, defibrillators, or cardioverters "shock" the heart back into a normal heart rhythm. Sometimes the devices are external, such as in an emergency situation. Often, the electronics are implanted in the patient’s chest.
  • Implanted Cardioverter Defibrillators (ICDs) — ICDs are 99 percent effective in stopping life-threatening arrhythmias and are the most successful therapy to treat ventricular fibrillation, the major cause of sudden cardiac arrest. ICDs continuously monitor the heart rhythm, automatically function as pacemakers for heart rates that are too slow, and deliver life-saving shocks if a dangerously fast heart rhythm is detected.
  • Pacemakers — Devices that “pace” the heart rate when it is too slow (bradycardia) can take over for the heart’s natural pacemaker, the sinoatrial node, when it is functioning improperly. Pacemakers monitor and regulate the rhythm of the heart and transmit electrical impulses to stimulate the heart if it is beating too slowly.
  • Devices for Heart Failure — The U.S. Food and Drug Administration (FDA) approved a special type of pacemaker for certain patients with heart failure. In Cardiac Resynchronization Therapy, an implanted device paces both the left and right ventricles (lower chambers) of the heart simultaneously. This resynchronizes muscle contractions and improves the efficiency of the weakened heart.
  • Surgery — Although surgery is sometimes used to treat abnormal heart rhythms, it is more commonly elected to treat other cardiac problems, such as coronary artery disease and heart failure. Correcting these conditions may reduce the likelihood of arrhythmias.

¹Go, AS, Hylek, EM, Phillips KA, Chang, Y, Henault LE, Selby JV, Singer DE. Prevalence of diagnosed atrial fibrillation in adults. National implications for rhythm management and stroke prevention: the Anticoagulation and Risk Factors In Atrial Fibrillation (ATRIA) Study. JAMA 2002;285:2370-2375.
²MMWR, February 21, 2003/52(07); 128-131: Public Health and Aging: Atrial Fibrillation as a Contributing Cause of Death and Medicare Hospitalization — United States, 1999.
³Same as above.
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