Atrial ectopic activity associated with sinus bradycardia.

Five cases of atrial ectopic activity associated with sinus bradyeardia are reported. The ectopic activity was abolished in all cases when the sinus rate was increased spontaneously or by atropine. The report demonstrated that the incidence of ectopic activity increases in the atrium at the slower basic rates as it does in the ventricle. It was emphasized that atrial ectopic activity associated with sinus bradycardia should be treated by atropine or by rapid pacing of the atrium because atrial premature beats have the potential of inducing more serious atrial tachyarrhythmias. The possible role of the vagus nerves in facilitating the induction of atrial tachyarrhythmias was discussed, and it was suggested that atropine may have an added benefit of reducing the likelihood of development of atrial tachyarrhythmias.