[Frequency dependent prolongation of inter-atrial conduction time by mexiletine in human atrium].
To investigate frequency dependent conduction slowing by mexiletine in the human atrium, we examined inter-atrial conduction time (IACT) at different stimulation frequencies (100/min to 220/min) in 13 patients with paroxysmal atrial fibrillation (Paf) and 7 patients without Paf. IACT was prolonged as the stimulation frequency was increased, and either before or after mexiletine administration IACT was longer in the Paf group (max 114 +/- 9 msec, p < 0.01, mean +/- SD) at any stimulation frequency than in the non-Paf group (max 100 +/- 8 msec). The change in IACT induced by mexiletine administration (% delta IACT) was larger in the Paf group (max 14.8 +/- 5.4%, p < 0.05) than in the non-Paf group (max 5.5 +/- 2.2%) at stimulation frequency over 140/min. Effective refractory period measured at the high right atrium was slightly decreased due to mexiletine in both the non-Paf and the Paf group. In conclusion, mexiletine showed frequency dependent suppression of conduction in the human atrial myocardium especially in patients with Paf.
Sakai
R
R
Second Department of Medicine, Kyoto Prefectural University of Medicine.
Inoue
D
D
Ishibashi
K
K
Inoue
M
M
Omori
I
I
Yamahara
Y
Y
Asayama
J
J
Nakagawa
M
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology; D004594:Electrophysiology; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008801:Mexiletine / Q000494:pharmacology*; D008875:Middle Aged
D008801:Mexiletine