title: Double atrial parasystole showing intermittent trigeminy.
abstract: Atrial parasystole arising from two different ectopic atrial foci, namely, double atrial parasystole, showed intermittent trigeminy due to 3:1 exit block, in which both the ectopic atrial rates were around the sinus rate. Atrial trigeminy showing positive P waves in leads II and III continued, then intermittent atrial parasystole with negative P waves in leads II and III took over. The double atrial parasystole was considered to be interspersed with reentrant atrial beats. Other possible mechanisms to cause a disruptive influence on the trigeminy of the atrial parasystole with positive P waves in leads II and III are: (a) concealed intraatrial reentry with resetting by the sinus impulse; and (b) delayed capture by the impulse of the third preceding sinus beat, and the subsequent 3:1 exit block. On the other hand, the atrial parasystole with negative P waves in leads II and III tended to show long interectopic intervals, in which some of the parasystolic beats exhibited a coupling to the third preceding sinus beat. This suggested prompt resetting by the sinus impulse and the ensuing 3:1 exit block.
authors.affiliation: Mouridai Clinic, Kanagawa, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Izumi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005117:Cardiac Complexes, Premature / Q000175:diagnosis*; D004562:Electrocardiography; D006801:Humans; D008297:Male