(A) Study protocol. ECL2 was injected at four time points and per stage persisted 2 weeks (control group, n=10; β1-AAb group, n=8; bisoprolol group, n=8). Bisoprolol was administered after 8-week active immunization for 2 weeks. Seven animal models per group were chosen for the next experiments. (B) Heart rate monitoring of three groups at the end point of each in vivo experiment (n=7) per group. (C) calculation of P wave dispersion from ECG results (n=7) per group. (D) Plasma β1-AAb concentrations of three groups at five time points, (n=7) per group, *P<0.05 vs. baseline of each group at different time points; ^#P<0.05 vs. control group at same time points among different groups. (E) Detection of atrial cAMP contents of three groups after extracting atrial tissues, (n=7) per group. *P<0.05 as indicated, and ns indicates no significance.