INCIDENCE OF INDUCED ATRIAL FIBRILLATION FLUTTER IN COMPLETE ATRIOVENTRICULAR-BLOCK - A CONCEPT OF ATRIAL-MALFUNCTIONING ATRIO-HISIAN BLOCK/

Background Atrial fibrillation/flutter (Af) has been considered to occ ur coincidentally with atrioventricular (AV) block. However, a case wi th complete AV block was reported to histologically show fibrotic chan ges solely in the atrial muscles but neither in the AV node nor in the His bundle, indicating a possible relation between AV block and atria l tachyarrhythmias. To test a hypothesis that AV block and Af are caus ally interrelated, we investigated the incidence and electrophysiologi cal characteristics of Af in complete AV block. Methods and Results Fo rty-two patients with persistent complete AV block underwent the elect rophysiological study. Patients with spontaneous/electrically induced Af were compared with the other patients with respect to their electro physiological variables. Of the 42 patients, Af was transiently induce d by electrical stimulation in 5 patients (11.9%), while persistent Af was observed in 2 patients (4.8%, AH and HV block). AV block in the 5 patients with induced Af was invariably due to AH block. AH block com plicated by persistent/induced Af was marked by relatively short RR in tervals, significantly short junctional recovery time, and impaired in tra-atrial conduction. Conclusions Electrically induced Af in complete AV block was associated frequently with complete AH block. These pati ents were characterized differently from the commonly recognized AV bl ock and therefore may stand as a unique subgroup of AH block.