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Related to arrhythmia: atrial fibrillation


arrhythmia (ārĭᵺˈmēə), disturbance in the rate or rhythm of the heartbeat. Various arrhythmias can be symptoms of serious heart disorders; however, they are usually of no medical significance except in the presence of additional symptoms. The heart's rhythm is controlled by an electrical impulse that is generated from a clump of tissue on the right atrium called the sinoatrial node, often referred to as the heart's natural pacemaker. It travels to a second clump of tissue called the atrioventricular node and then to the ventricles.

Bradycardia, or slow heartbeat, is often present in athletes. It may, however, indicate conduction problems, especially in older people. In one type of bradycardia, called sinoatrial or atrioventricular block, or heart block, rhythm can be maintained by implanted electrodes that act as artificial pacemakers.

Tachycardia, or heartbeat faster than 100 beats per minute in the adult, can be precipitated by drugs, caffeine, anemia, shock, and emotional upset. It may also be a sign of overactivity of the thyroid gland or underlying disease. Flutters, and the even faster fibrillations, are rapid, uncoordinated contractions of the atrial or ventricular muscles that usually accompany heart disorders. Atrial fibrillation may be idiopathic, the result of rheumatic mitral valve disease (see rheumatic fever) in young people or hypertensive heart disease (see hypertension) and arteriosclerotic heart diseases (see arteriosclerosis) in older people. It may result in a rapid pulse rate and may be associated with thrombus formation in the atria and a risk of embolization to the brain (stroke) or other organs. Atrial fibrillation is often treated with digitalis and other drugs that regulate heart rhythm or heart rate. It may also be treated by catheter ablation, in which an electrode produces heat to destroy cells causing the arrhythmia. Ventricular fibrillation is a sign of the terminal stage of heart failure and is usually fatal unless defibrillation is achieved by immediate direct-current defibrillation. Some tachycardias can be managed by the implantation in the upper chest of small defibrillators that sense dangerous fibrillations and administer an electric shock to the heart to restore normal rhythm.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



disruption of the normal rhythm of the heart. Arrhythmia is manifested as an increase in frequency (tachycardia) or a slowing (bradycardia) of the heart contractions, in the appearance of premature or additional contractions (extrasystole), in heart palpitations (paroxysmal tachycardia), and in complete irregularity of the intervals between individual contractions (fibrillation). Arrhythmia may appear, among other causes, as a result of heart disease (myocarditis, cardiosclerosis); it may be functional or be caused by disturbance of the nervous regulation of the heart—for example, when the interconnection between the auricles and ventricles is interrupted (heart block). So-called respiratory or juvenile arrhythmia (acceleration of heartbeat upon inspiration) is a physiological phenomenon in children and adolescents. Some arrhythmias cause disturbance of blood circulation, unpleasant feelings of “irregularity of heart action,” dizziness, and the like. Other arrhythmias are not felt by patients. Treatment is directed toward removing the basic disease and restoring the normal heart rhythm.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Absence of rhythm, especially of heart beat or respiration. Also spelled arhythmia.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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Atrial fibrillation is a type of arrhythmia that affects the atria, the heart's upper two chambers.
An ICD is essentially one step up from a pacemaker, and delivers a mild-to-moderate electrical shock to reset the heart if a serious arrhythmia is detected.
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Furthermore, the major limiting factor was the frequency of symptoms itself, which may be complicated by the fact that the same arrhythmia may occur with different symptoms over a course of time.
Frequent irregularities in the triggering the normal pattern electric impulses lead to cardiac arrhythmia.
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