Electrocardiographic and Chronobiological Features of Paroxysmal AV Block Recorded by Ambulatory Electrocardiography

The goal of this study was to investigate the electrocardiographic and chronobiological features of paroxysmal atrioventricular (AV) block (PAVB) using data from ambulatory electrocardiography (AECG). The study population consisted of five men and six women aged from 47 to 82 years of age. Main presenting symptoms were pre-syncope in five patients (45.5%) and syncope in three patients (27.3%). Organic cardiovascular diseases were seen in eight patients (72.7%), and AV conduction disturbances were seen in six patients (54.5%), such as right bundle branch block, first to second degree AV block on standard 12-lead electrocardiography. Incidence of PAVB events were 1-329 (37.9±98.0) episodes/patient/day, and the maximum pause during Holter recordings was 3.3-12.4 (6.39±3.09) seconds. This maximum pause caused by intrinsic AV block was longer than that of vagally mediated AV block (8.4±3.2 sec vs 4.7±1.0 sec, p<0.05). In chronobiological analysis, episodes of PAVB exhibited a circadian rhythm characterized by a peak between 2 : 00 am and 4 : 00 am and a trough between 0 : 00 pm and 2 : 00 pm. AECG is a useful tool to detect the maximum pause occurring during sleep and provides critical data necessary to prevent the sudden cardiac death caused by PAVB.