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Premature beat of the heart.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the most common form of arrhythmia. The condition is characterized by irregular heart contractions (extra-systoles) caused by impulses from an additional focus of excitation arising in the myocardium. Since the heart muscle remains unexcitable for some time after every contraction, the next normal impulse usually cannot cause a systole. As a result, a longer than normal contraction, that is, a compensatory pause, occurs. An extrasystole is generally felt as a temporary sinking sensation, or an “interruption in the heart.” Atrial extrasystoles arise in the atria, and ventricular extrasystoles in the ventricles. Extrasystoles may be single or multiple, and they may occur chaotically or with a certain rhythm, for example, after every normal contraction (bigeminal). Sometimes several extrasystoles occur in succession.

Extrasystoles can occur in healthy persons, and, in most cases, occasional infrequent extrasystoles have little clinical significance. Atrial extrasystoles, however, may result from myocardial disease, for example, mitral insufficiency or cardiosclerosis. Frequent atrial extrasystoles in these diseases are an early sign of auricular fibrillation, especially when they occur in rapid succession. Ventricular extrasystoles may result from myocardial disease or neurological, mental, and other disorders. Successive ventricular extrasystoles originating from different places may precede a severe form of arrhythmia called ventricular fibrillation.

Electrocardiography plays an important part in diagnosing ex-trasystoles. Treatment is determined by cause. The administration of antiarrhythmic agents, for example, propranolol and potassium preparations, is sometimes required.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In particular, available covariates that are known to affect extrasystolic occurrence [11, 16] were compared between the cohorts (age, gender, hypertension, and heart disease; heart disease was defined dichotomously as any presence of congestive heart failure, cardiac arrhythmia, valvular disease, pulmonary circulation disorders, or peripheral vascular disorders in the Elixhauser subitems, which are based on ICD9 and drug codes).
Extrasystolic coverage's dependence on demographic and relevant clinical factors was analyzed in three multivariate linear regression models which all included gender, age, hypertension, and heart disease.
The not-analyzable records were assigned an extrasystolic coverage of 0%.
These results are quite matched with data obtained at estimation of inotropic reaction of papillary muscles of the animals of II and III groups on extrasystolic action.