Heart rhythm disorders – causes, mechanisms of development
Diagnosis of cardiac arrhythmias is one of the tasks of electrocardiography since the invention of this method. Usually, a rhythm disturbance can be correctly interpreted by an ECG recorded in one lead, for example, lead II. In recent years, the problem of rhythm disturbances has become increasingly urgent.
With the advent of electrotherapy in the 1960s, carried out, on the one hand, by using an electric defibrillator and implantable pacemaker, on the other, by new antiarrhythmic drugs and interventional electrophysiology, including catheter ablation, the treatment of heart rhythm disturbances acquired a new dimension.
To apply these new treatments, an accurate analysis of the heart rhythm was required. Thus, at present, various methods are used for the study of patients, for example, long-term ECG monitoring, exercise ECG test, GHG electrography and electrical stimulation of the atria and ventricles, as well as electrophysiological research, which will be mentioned separately.
The main prerequisite for successful treatment of cardiac arrhythmias is their correct diagnosis. Often, the rapid recognition of severe arrhythmia allows you to prescribe a salvage therapy; cases of rapid and successful treatment of cardiac arrhythmias are observed in clinical practice more often.
At the same time, even today, ECG is a routine method for diagnosing cardiac arrhythmias, which is of great importance in clinical practice and makes it possible to determine the need for research with more complex and modern diagnostic methods. In the mechanism of arrhythmia, a role is played by a violation of myocardial excitability or a violation of its conductivity.
Currently, a number of theories have been proposed to explain the pathogenesis of cardiac arrhythmias, for example:
• increase of heart automatism (for example, with sympathicotonia);
• activation of the ectopic focus of excitation (for example, during ischemia);
• trigger activity (change in aftereffect potentials);
• re-entry of the excitation wave (re-entry mechanism).
These theories can be divided into 2 groups: one group explains the occurrence of arrhythmia by impaired excitability of a specific area of the myocardium, such as the atrium or ventricle, the other by impaired myocardial conductivity and the formation of a circular excitation wave.