Ectopic atrial tachycardias is a group of supraventricular arrhythmias, characterized by the presence of areas of conductive tissue generating impulse and eccentrically propagating it to the myocardium with the suppression of sinus rhythm. The presence of these zones, as well as their participation in the generation and conduction of impulse raises many questions. Are there prerequisites for the development of so-called "transition zones" or they appear secondary – this is one of the main issues of the etiopathogenesis of ectopic atrial tachycardia. Treatment of these types of cardiac arrhythmias still poses a problem for a practical physician, which is caused by the transient nature of arrhythmias and, in some cases, asymptomatic clinical course, making it difficult to detect and diagnose. Identificating the mechanism and source of arrhythmia plays a leading role in choosing the method of treatment. In this regard, modern algorithms of the mechanism of arrhythmias verification which allow to select protocols of diagnostics and catheter treatment are extremely necessary in clinical practice. Their current coverage is offered in this review. The latest data on the embryogenetic features of the conductive tissue development, as well as the developmental disturbances, subsequently leading to the emergence of "transition zones" are presented. We analysed histological aspects of "transition zones" verification and marked classical histological criteria and immunohistochemical modern tests that allow to verify zones of disembriogenesis. The places of the most probable localization of ectopias in the right and left atriums are demonstrated. The problems of catheter treatment in terms of location of electrodes and their application points to endocardium are discussed, allowing to minimize recurrences of ectopias and to increase the effectiveness of treatment. The unified parameters of ablation which proved to be the most effective in practice for ectopic atrial arrhythmias treatment are also presented. The indications for open surgical interventions are highlighted. The importance of open surgical intervention which allows to eliminate ectopia after a number of unsuccessful radiofrequency influences is noted.