The Role Of Bachmann's Bundle In Sustained Vagotonic Atrial Fibrillation In Canines

Background Vagotonic atrial fibrillation is an important type of clinical atrial fibrillation. Vagal nerve stimulation can shorten atrial effective refractory period (AERP), increase dispersion of ERP, make atrial fibrillation easy to initiate and sustain. Bachmann's bundle (BB) is the most important interatrial connection. It play an important role in the atrial arrhythmia, but we don't know the role of BB in the vagotonic atrial fibrillation. This study is to investigate the role of Bachmann's bundle (BB) in the maintenance of sustained vagotonic atrial fibrillation in canines.Methods Cervical vagal stimulation was performed in 8 canines. All canines were instrumented with epicardial electrodes patches on free walls of both right and left atrial appendage. Sustained AF was induced by burst atrial stimulation. BB ablation was achieved using radiofrequency catheter ablation epicardially. Atrial effective refractory period (AERP), atrial fibrillation cycle length (AFCL), AERP difference between left and right atrium, conduction characters of BB, conduction time between left and right atrium, inducibility and duration of AF were measured before and after BB ablation during vagal stimulation.Results Eight canines were studied. After ablation of BB, conduction between LA and RA prolonged significantly (.P<0.01). AERP change from 108.7±3.0 ms to 112.0±L6.7 ms (P>0.05) at the left atrium and from 116.0±8.9 ms to 111.6±14.0 ms (P>0.05) at the right atrium. Before ablation of BB, AFCL of left and right atrium and BB were 88.4±8.0 ms, 84.3±13.2 ms and 90.9±18.5 ms, respectively. After ablation of BB, AFCL of left and right atrium and BB were 107.1±17.2 ms (P<0.05, vs. pre-ablation),105.4±12.3ms (P<0.05, vs. pre-ablation) and 118.5±9.5 ms (P<0.05, vs.pre-ablation) respectively. Complex fractionated atrial electrograms reducedsignificantly in BB after ablation of BB. Before ablation, sustained atrialfibrillation could be induced in eight canines. After ablation, sustained atrialfibrillation could be induced in three canines. In other five canines, AFterminated spontaneously in 30 seconds.Conclusion Bachmann's bundle may play a role in the perpetuation ofvagotonic AF in canines.