Sinus modulation of atrial parasystole

Recognition of atrial parasystole may be difficult if the characteristic features are absent. Thus, ectopic atrial beats can be associated with fixed coupling intervals, as a manifestation of "reversed coupling," and atrial fusion beats may be absent.1,2 We report a patient with atrial parasystole in whom the ectopic atrial pacemaker was electronically modulated by sinus impulses. This resulted in an irregular ectopic discharge so that the characteristic mathematical relation between the interectopic intervals was distorted and not apparent. © 1986.