[Electrophysiologic effects of flecainide on guinea pig atrium].
We investigated the effects of flecainide on guinea pig atrial muscle. Using Langendorff's method, the whole heart of a guinea pig was perfused with Tyrode's solution containing acetylcholine (3 x 10(-7) M). Then, with right atrial extrastimulus and high frequency pacing method, the following values were measured before and after administration of flecainide (10(-7)-10(-5) M). A) Effective refractory period (ERP); the longest coupling interval which failed to produce right atrial activity at premature stimulus. B) Interatrial conduction time (ACT); After right atrial stimuli by trains at PCL 200 ms for 5 min the interval from the stimulation to the first deflection of the left atrial activity. C) Atrial fibrillation threshold (AFT); the minimal amount of current required to induce atrial fibrillation lasting for more than 30 sec by 50 Hz high frequency stimulation. Flecainide lengthened ERP (> or = 3 x 10(-5) M) and ACT (> or = 10(-7) M). Flecainide (10(-5) M) significantly increased AFT which correlated well with ERP (r = 0.81, p < 0.002) and ACT (r = 0.84, p < 0.002). In conclusion these effects of flecainide on guinea pig atrium might explain in part the clinical effectiveness of the drug on paroxysmal atrial fibrillation.
Inoue
M
M
Second Department of Medicine, Kyoto Prefectual University of Medicine.
Inoue
D
D
Shirayama
T
T
Sakai
R
R
Matsumoto
T
T
Yamahara
Y
Y
Asayama
J
J
Katsume
H
H
Nakagawa
M
M
Omori
I
I
D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology; D016275:Atrial Function; D004558:Electric Stimulation; D004594:Electrophysiology; D005424:Flecainide / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D012032:Refractory Period, Electrophysiological / Q000187:drug effects
D005424:Flecainide