title: Cholinergically mediated tachyarrhythmias induced by a single extrastimulus in the isolated canine right atrium.
abstract: Cholinergic agonists and vagal stimulation potentiate the inducibility of atrial fibrillation. To describe the activation patterns and determine the mechanisms that sustain cholinergic fibrillation, tachyarrhythmias were induced with a single extrastimulus in the isolated Krebs-Henseleit-perfused canine right atrium (n = 11) at increasing concentrations of acetylcholine (from 10(-7.5) to 10(-4.5) M). Bipolar electrograms were recorded from 250 epicardial sites simultaneously during control conditions and during extrastimulation (S1S1, 300 msec; S1S2, effective refractory period+5 msec) with and without acetylcholine. Activation sequence maps were constructed from each recording. Without acetylcholine, no tachyarrhythmias were induced. With increasing concentrations of acetylcholine, the refractory period decreased, and nonsustained (< 2 seconds) rapid repetitive responses were induced. At higher concentrations, a sustained (> 2-minute) fibrillation was induced. Activation sequence maps revealed that the rapid repetitive responses were characterized by multiple reentrant circuits. The number of circuits and wavelets increased in a dose-dependent fashion. However, unexpectedly, this trend did not continue when the tachyarrhythmia became sustained. Instead, the reentry tended to stabilize to a small, single, relatively stable reentrant circuit. In conclusion, the data suggest that, in this model, below a critical level of refractory period (< 95 msec) atrial reentrant circuits, unassociated with anatomic obstacles, can become stable and dominate activation.
authors.affiliation: Department of Surgery, Washington University School of Medicine, Barnes Hospital, St. Louis, MO 63110.
authors.forename: R B
authors.initials: RB
authors.lastname: Schuessler
authors.forename: T M
authors.initials: TM
authors.lastname: Grayson
authors.forename: B I
authors.initials: BI
authors.lastname: Bromberg
authors.forename: J L
authors.initials: JL
authors.lastname: Cox
authors.forename: J P
authors.initials: JP
authors.lastname: Boineau
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology; D016275:Atrial Function; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004285:Dogs; D004594:Electrophysiology; D006321:Heart / Q000502:physiology*; D009994:Osmolar Concentration; D051381:Rats; D012032:Refractory Period, Electrophysiological; D013610:Tachycardia / Q000209:etiology*
chemical_list: D000109:Acetylcholine