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 occur coincidentally with atrioventricular (AV) block. However, a case with complete AV block was reported to histologically show fibrotic changes solely in the atrial muscles but neither in the AV node nor in the His bundle, indicating a possible relation between AV block and atrial tachyarrhythmias. To test a hypothesis that AV block and Af are causally interrelated, we investigated the incidence and electrophysiological characteristics of Af in complete AV block.

METHODS AND RESULTS

Forty-two patients with persistent complete AV block underwent the electrophysiological study. Patients with spontaneous/electrically induced Af were compared with the other patients with respect to their electrophysiological variables. Of the 42 patients, Af was transiently induced 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 complicated by persistent/induced Af was marked by relatively short RR intervals, significantly short junctional recovery time, and impaired intra-atrial conduction.

CONCLUSIONS

Electrically induced Af in complete AV block was associated frequently with complete AH block. These patients were characterized differently from the commonly recognized AV block and therefore may stand as a unique subgroup of AH block.