Extrasystole is a type of arrhythmia that occurs as a result of abnormal automatism and the re-entri mechanism and manifests itself as an early contraction of the heart or any of its departments. Extrasystoles, causes and the place of occurrence of early arousal, are different. Depending on the place of occurrence, they distinguish: atrial, ventricular extrasystoles and contractions that occur in the atrioventricular connection.
Extrasystoles, the causes of which are determined by the time of appearance, are called early and late. The time that elapses from the previous complex to the appearance of a new extrasystole is called the preectopic interval (cohesion time). It is strictly fixed, which indicates a common source of early arousal. The uneven duration of the intervals is associated with extrasystoles from different sites. At the same time, their shape also changes.
The close connection between the appearance of an early contraction and the main heart rhythm is due to the appearance of extraordinary stimuli by the main (normal) impulses - the mechanism of post-depolarization, non-synchronous repolarization or re-entri.
The features of extrasystoles are also noted by the subsequent pause, this is the period of time that elapses between the early contraction and the subsequent impulse of the main rhythm. The duration of this pause depends on whether or not the discharge of the sinus node has occurred. When the sinus node is discharged by an ectopic pulse, which was formed as a result of early excitation of the atria, a new impulse begins to form in it with a period of time equal to the main sinus rhythm. Then the magnitude of the pre- and postectopic intervals is less than the duration of two normal cardiac cycles, this is an incomplete compensatory pause. If discharge of the main node by the extrasystole does not occur, a complete pause occurs, that is, the sum of the values of the pre- and post-ectopic intervals is equal to the duration of two normal cardiac cycles.
Extrasystoles, the causes of their appearance, are determined by the frequency and time of their appearance. Infrequent early contractions (for example, extrasystoles after eating) have almost no effect on hemodynamics, but sometimes they can have prognostic value, being a harbinger of more serious rhythm disturbances. Permanent extrasystoles, which alternate with a normal rhythm, are complicated by hemodynamic disorders. If three premature contractions are recorded in a row, this situation is interpreted as paroxysm of tachycardia. Cardiac fibrillation may occur if early premature contractions occur, combined with impaired metabolic processes in the myocardium.
Early contractions occurring in the atrium are manifested by the appearance of the P wave, which differs from the normal form and duration. The QRS complex itself remains the same. Contraction from the ventricular-atrial connection on the cardiogram is manifested by an altered ventricular complex. P wave is absent, since the excitation in the atria coincides with the excitation of the ventricles. If ventricular contraction occurs earlier than the atria, the P wave is negative and appears after the ventricular complex.
Early ventricular contractions on the cardiogram are visible as an early ventricular complex, having a supraventricular form. Before the extrasystole there is no P wave, the ventricular complex is expanded and changed. Extrasystoles of the left ventricle are manifested by blockade of the right leg of the bundle of His, and vice versa.
Extrasystoles, the causes of their appearance
Early contractions can accompany any heart disease, but can also occur on their own, due to diseases of the nervous system, overdose of drugs, electrolyte disturbances, and the use of large quantities of alcohol.
How to get rid of extrasystole
All factors contributing to early reduction must be addressed. Prescribing drugs calming the nervous system. Rare reductions do not require special treatment. With a combination of extrasystoles with hypertension, antihypertensive and antiarrhythmic drugs (propranolol, verapamil, etc.) are prescribed, potassium preparations, if there are no contraindications to them.