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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 It might be outdated or ideologically biased.



an increase in the frequency of cardiac contractions. In some cases it is not perceived subjectively; in others, it is accompanied by palpitations.

A distinction is made between sinus tachycardia, or the accelerated generation of impulses in the sinus node of the heart, and paroxysmal tachycardia. Sinus tachycardia, manifested by contractions generally ranging between 90 and 120 per minute, may be caused by such physiological factors as increased environmental temperature, physical and mental tension, or the ingestion of food. Sinus tachycardia may also be caused by such pathological states as fever, anemia, diffuse toxic goiter, heart failure, and neurasthenia. Nervous and humoral influences on the heart, such as adrenalin and thyroxine, are important contributing factors in the genesis of sinus tachycardia. The accelerated rhythm of cardiac contractions may have an unfavorable effect on metabolism in the myocardium and on blood circulation. When tachycardia is a symptom of disease, the underlying disease is treated.

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


Excessive rapidity of the heart's action.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
(c) Atrial tachycardia was documented on twenty-four-hour ambulatory Holter monitoring before the operation.
Out of 50 patients with narrow complex tachycardia, 28 (56%) patients were of atrioventricular nodal reentry type (AVNRT), 17 (34%) patients were of atrioventricular reentrant tachycardia type (AVRT), 4 (8%) patients were of atrial tachycardia and only one (2%) patient was of atrial fibrillation type.
Out of which pathways were 131 (124 patients were having Wolff-Parkinson-White (WPW) and orthodromic reciprocating tachycardia7), atrial tachycardia (AT) 5 and 133 were atrio-ventricular reentry tachycardia (AVNRT).
An irregular rhythm and the absence of P waves (or the presence of fibrillatory waves) characterizes atrial fibrillation; irregularity and [greater than or equal to] 3 different P wave morphologies is suggestive of multifocal atrial tachycardia. Other possibilities include frequent premature atrial contractions or a sinoatrial or AV nodal conduction block.
For example, if the RP interval is significantly shorter during ventricular pacing than during tachycardia, the P wave is not likely to be retrograde and the diagnosis is likely to be sinus or ectopic atrial tachycardia. Pacing manoeuvres do not usually terminate JET; other forms of supra-ventricular tachycardia (SVT) should be considered if this occurs.
Focal atrial tachycardia originating from the musculature of the coronary sinus.
The term incisional atrial tachycardia is used when the re-entry zone is localized around postoperative scar1.
A meta-analysis including 109,798 patients revealed patients who are taking PPIs are at higher risk of hypomagnesemia, which has been associated with various cardiovascular arrhythmias including widening QRS complexes, frequent atrial and ventricular premature systoles and sustained atrial fibrillation.3 A study done on patients with focal atrial tachycardia (AT) and right ventricular outflow tract ventricular tachycardia (RVOT VT) revealed increased odds of focal arrhythmias and RVOT VT associated with use of PPIs.4
The patient's subsequent ECGs demonstrated various cardiac arrhythmias including sinus rhythm with premature atrial contractions, sinus arrhythmias, and multifocal atrial tachycardia (Figure 2) which spontaneously resolved.
Procedures performed among 163 patients who underwent a cryoablation procedure Procedure N (%) Cryoablation pulmonary vein isolation 163 (100.0%) Cryoablation plus radiofrequency to 18 (11.0%) complete the pulmonary vein isolation Cryoablation plus balloon lesions to 20 (12.3%) nonpulmonary vein areas Cryoablation plus radiofrequency to 17 (10.4%) nonpulmonary vein areas Cryoablation plus typical atrial 33 (20.3%) flutter ablation Cryoablation plus ablation on 1 (0.6%) nonpulmonary vein atrial tachycardia * Some patients had more than one concomitant site treated.
Lung disease may lead to atrial dilatation and AF, AFL or multifocal atrial tachycardia (MAT).