Time-dependent Cervical Vagus Nerve Stimulation and Frequency-dependent Right Atrial Pacing Mediated Inducibility of Atrial Fibrillation

Figure 1. Experimental study design. Atrial fibrillation (AF) was induced in dogs under systemic anesthesia as described in the Methods section. A total of 24 dogs were included in this study and were randomly categorized into four groups: the right cervical vagus trunk stimulation (RVTS) group, the rapid right atrial pacing group stimulated with a frequency of 500 beats/min (RAP500), the RAP500+RVTS group, and the rapid right atrial pacing group stimulated with a frequency of 1000 beats/min (RAP1000). Cardiac electrophysiological activities were recorded at the following sites—the left atrium (LA), the right atrium (RA), the left superior pulmonary vein (LSPV), and the left inferior vein (LIPV)

Figure 2. The RAP1000 group shows increased AF induction rate. AF was induced and recorded at the following positions–the left atrium (LA, Panel A), the right atrium (RA, Panel B), the left inferior pulmonary vein (LIPV, Panel C), and the left superior pulmonary vein (LSPV, Panel D). The RAP1000 group showed the highest AF induction rate in comparison to other groups. Meanwhile, the RAP500+RVTS group had a higher AF induction rate compared with that of the RAP500 group. *, p<0.05; **, p<0.01; ***, p<0.001; ****, p<0.0001, analyzed by two-way analysis of variance with Tukey post-hoc tests (n=6)

Figure 3. The RAP1000 group shows increased AF duration. AF was induced and recorded at the following positions–the left atrium (LA, Panel A), the right atrium (RA, Panel B), the left inferior pulmonary vein (LIPV, Panel C), and the left superior pulmonary vein (LSPV, Panel D). The RAP1000 group had a longer AF duration compared with that of other groups. Meanwhile, the RAP500+RVTS group had longer AF duration in comparison to the RAP500 group. *, p<0.05; **, p<0.01; ***, p<0.001; ****, p<0.0001, analyzed by two-way analysis of variance with Tukey post-hoc tests (n=6)

Figure 4. The RAP1000 group shows significantly shortened effective refractory period (ERP). AF was induced and recorded at the following positions–the left atrium (LA, Panel A), the right atrium (RA, Panel B), the left inferior pulmonary vein (LIPV, Panel C), and the left superior pulmonary vein (LSPV, Panel D). The RAP1000 group had a significantly shorter ERP compared with that of other groups. The RAP500+RVTS group had a shorter ERP compared with that of the RAP500 group. *, p<0.05; **, p<0.01; ***, p<0.001; ****, p<0.0001, analyzed by two-way analysis of variance with Tukey post-hoc tests (n=6)

Figure 5. The RAP1000 group shows the most prolonged dispersion of effective refractory period (dERP). AF induction and dERP measurement are described in the Methods section. The RAP1000 group had the most prolonged dERP. *, p<0.05; **, p<0.01; ****, p<0.0001 analyzed by two-way analysis of variance with Tukey post-hoc tests (n=6)