The article is dedicated to intracardiac echocardioscopy as a method of cavotricuspid isthmus morphology and variability accessing. The comparative characteristics of different diagnostic methods to investigate the anatomy of this region with advantages of proposed one is provided. The analysis of patients that undergone intracardiac echocardioscopy during catheter ablations of various arrhythmias is done. Anatomical variants of
cavotricuspid isthmus, their prevalence with marking of the three common types of the structure (I, C и S) are described. Other specific features (long eustachian ridge, deep subeustachian pouch, etc.), which may
potentially challenge the implementation of cavotricuspid isthmus catheter ablations are clarified.