Induction of atrial tachycardia and fibrillation in the mouse heart

Background: Atrial tachycardia and fibrillation in humans may be partly con sequent to vagal stimulation. Induction of fibrillation in the small heart is considered to be impossible due to lack of a critical mass of >100-200 m m(2). Even with the recent progression of the technology of in vivo and in vitro mouse electrophysiological studies, few reports describe atrial tachy cardia or fibrillation in mice. The purpose of this study was to attempt pr ovocation of atrial tachyarrhythmia in mice using transvenous pacing follow ing cholinergic stimulation. Methods and results: In vivo electrophysiology studies were performed in 14 normal mice. A. six-lead ECG was recorded fro m surface limb leads, and an octapolar electrode catheter was inserted via jugular vein cutdown approach for simultaneous atrial and ventricular endoc ardial recording and pacing. Atrial tachycardia and fibrillation were induc ible in one mouse at baseline electrophysiology study and eleven of fourtee n mice after carbamyl choline injection. The mean duration of atrial tachyc ardia was 126 +/- 384 s. The longest episode lasted 35 min and only termina ted after atropine injection. Reinduction of atrial tachycardia after admin istration of atropine was not possible. Conclusion: Despite the small mass of the normal mouse atria, sustained atrial tachycardia and fibrillation ca n be easily and reproducibly inducible with endocardial pacing after cholin ergic agonist administration. This finding may contribute to our understand ing of the classical theories of arrhythmogenesis and critical substrates n ecessary for sustaining microreentrant circuits. The techniques of transcat heter parasympathetic agonist-mediated atrial tachycardia induction may be valuable in further murine electrophysiological studies, especially mutant models with potential atrial arrhythmia phenotypes. (C) 2001 Elsevier Scien ce B.V. All rights reserved.