gms | German Medical Science

Firstly, the purpose of this study was to determine whether the injection of acetylcholine (Ach) to subadventitia layer of pulmonary veins (PVs) could initiate atrial fibrillation (AF). When the first purpose could be successful, the second purpose was to compare effects of Ca++ blocker verapamil, beta-blocker landiolol and the ligation of the left atrium (LA) appendage in preventing AF. Twelve beagle dogs were anesthetized by thyamilal and alpha-chloralose and were ventilated with room air. The heart was in a pericardial cradle. Surface ECG and electrograms on PVs and LA appendage were recorded. In addition, activation time mapping with 64 electrodes on the LA appnedage was performed and effective refractory periods (ERP) on PVs were measured. Ach injection (100-500 micrograms/kg) or subsequent electrical stimulation (4 mA, 2 msec in width) to PVs could reproducibly induce AF. In a preliminary study, pre-injection of M2 blocker atropine, which was injected to the same site as Ach injection, prevented AF after the subsequent Ach injection in all dogs tested. In this study, pre-injection of verapamil prevented AF initiation after the subsequent Ach in 3 of the 4 dogs. In contrast, pre-injection of landiolol had no effects on AF prevention in all 4 dogs. The ligation of LA appendage root ceased AF during AF initiated by Ach, and prevented AF initiation after the subsequent Ach injection in all 4dogs. After Ach injection, activation mapping on the LA appendage showed more homogeneous conduction after the ligation than that before the ligation. ERPs on the PVs after the ligation were markedly prolonged as compared to those before the ligation (p<0.01). Consequently, AF initiated by acetylcholine injection to the subadventitia layer of pulmonary veins, in part, may depend on Ca++ current. LA appendage is suggested to be related to the maintenance of AF, not the initiation.