ECG tracings illustrating the negative dromotropic effect of neurostimulation during AF and its dependence on muscarinergic receptor activation. ( A ) Atrial fibrillation with rapid ventricular rate but without PS. ( B ) Neurostimulation with a stimulation voltage of 7.5 V, impulse duration of 0.5 ms, and stimulation frequency of 20 Hz results in a significant reduction of the average ventricular rate from 166 to 86 bpm. ( C ) Administration of 1 mg atropine iv increases heart rate to 230 bpm without neurostimulation. ( D ) After injection of atropine, the neurostimulation effect is no longer reproducible. Paper speed 25 mm/s.