Idiopathic paroxysmal atrioventricular block

   The article presents a clinical case of paroxysmal atrioventricular block, which is a rare and difficult to diagnose cause of syncope, which makes it difficult for specialists to make a correct diagnosis and determine the tactics of patient management.   Purpose. To demonstrate a clinical case, in which comprehensive methods of examination were carried out to identify the cause of syncope, and to show the need of understanding its pathogenesis.   For differential diagnosis, it is necessary to carry out not only routine examination methods, but also to use drug tests, as well as long-term monitoring devices (multi-day daily Holter monitoring, loop recorders of long-term ECG recording, smart watches, etc.), which help to find the cause of syncope. According to the clinical recommendations, patients with atrioventricular block and clinical symptomatology, require continuous cardiac pacing in order to prevent asystole with potential sudden cardiac death.