Mechanisms of atrial tachyarrhythmia induction in a canine model of autonomic tone fluctuation.
BACKGROUND
The purpose of this study was to investigate the effect of cholinergic modulation in the presence of increased adrenergic tone (i. e., autonomic fluctuation) on atrial tachyarrhythmia (AT) induction.


RESULTS
High-resolution optical mapping was used to measure action potentials from the left atrium in isolated arterially perfused canine atrial preparations. Optical recordings were made in the presence of isoproterenol during electrical stimulation of a fat pad at the right pulmonary veinatrial junction (Group I, n = 6), during electrical stimulation of a fat pad locating the superior vena cava contacted by the right pulmonary artery (Group II, n = 4), and during acetylcholine (ACh; Group III, n = 4) infusion. In the presence of isoproterenol,each of the three different transitory cholinergic interventions induced spontaneous AT in all preparations. In Group I, AT induced from the right atrium was sustained. However, AT induced from the left atrium was not sustained (RRB) in Group I. In Groups II and III, AT induced from the left atrium as well as the right atrium were also sustained (BAF-AT). The A1A2 coupling interval was shorter when BAF-AT was induced than it was when RRB was induced. Mean cycle length of repetitive focal excitation was shorter during the initiation of BAF-AT compared to RRB. Isochrone maps during the initiation of AT demonstrated a macroreentry with lines of conduction block following a single extrasystole (27 %) and focal repetitive excitation (73 %).


CONCLUSIONS
These results suggest that transitory cholinergic activation in the presence of increased adrenergic drive in the left atrium causes a single premature extrasystole with a short coupling interval and a focal repetitive excitation with a short cycle length, which favors the generation of AT originating from the left atrium.
Hirose
Masamichi
M
Dept. of Molecular Pharmacology, Shinshu University School of Medicine Matsumoto, Nagano 390-8621, Japan. hirose@sch.md.shinshu-u.ac.jp
Imamura
Hiroshi
H
D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002799:Cholinergic Fibers / Q000502:physiology*; D004285:Dogs; D004558:Electric Stimulation; D006321:Heart / Q000503:physiopathology*; D006325:Heart Atria / Q000503:physiopathology; D066298:In Vitro Techniques; D007545:Isoproterenol; D008297:Male; D009129:Muscle Tonus / Q000502:physiology; D055095:Optics and Photonics; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*
D007545:Isoproterenol