Change of a rhythm of cardiac activity

Electrocardiography allows analyzing changes of a cardiac rhythm in details. In norm frequency of cardiac reductions is 60-80 in a minute, at more rare rhythm - a bradycardia - 40-50, and at more frequent - tachycardia - exceeds 90-100 and reaches up to 150 and more in a minute. The bradycardia is often registered at sportsmen in a condition of rest, and a tachycardia - at intensive muscular work and emotional excitation.

At young men regular change of a rhythm of cardiac activity in connection with breath - respiratory arrhythmia is observed. It consists that in the end of each exhalation frequency of cardiac reductions decreases.

Extrasystole. At some pathological conditions of heart the correct rhythm incidentally or regularly is broken by extraordinary reduction - extrasystole. If extraordinary excitation arises in sinoatrial node during that moment when the refractory period has ended, but next automatic impulse has not appeared yet, there comes early reduction of heart - sinus extrasystole. The pause going for such extrasystole lasts same time, as well as usual. At the person extrasystole can appear at presence of the centers of irritation in the myocardium, in the field of ventricle drivers of a rhythm. The influences acting in heart from central nervous system can promote by extrasystole.

Trembling and blinking of heart. In pathology it is possible to observe an original condition of a muscle of auricles or ventricles of the heart, which are called trembling and blinking (fibrillation). Thus there are extremely frequent and asynchronous reductions of muscular fibers of auricles or ventricles - up to 400 (at trembling) and up to 600 (at blinking) in a minute. As the main difference of fibrillation is non-simultaneity of reductions of separate muscular fibers of the given department of heart. At such reduction of a muscle of auricles or ventricles cannot carry out forcing of blood. At the person fibrillation of ventricles, as a rule, is fatal if immediately to not arrange for its termination. The most effective way of a stop of fibrillation of ventricles is influence strong (a pressure in some KV) the impact of an electric current causing simultaneously excitation of muscular fibers of ventricle then synchronism of their reductions is restored.

The electrocardiogram and VCG reflect changes of size and a direction of potentials of action of a myocardium, but do not allow to estimate feature of force function of heart.

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