title: Effect of 60 minutes of rapid atrial pacing on atrial action potential duration in the in-situ canine heart.
abstract: Right atrial monophasic action potentials were recorded before and after 60 minutes of rapid atrial pacing (pacing cycle length (CL); 127 +/- 10 ms) in 12 closed-chest dogs. The right atrial (RA) monophasic action potential (MAP) duration at 90% repolarization (RAMAPD) was measured at CLs of 400 ms and 250 ms. CL-dependent changes in RAMAPD (CL 400 ms - 250 ms) before and after rapid atrial pacing were 24 +/- 1 ms and 16 +/- 5 ms, respectively (p < 0.02). RAMAP was recorded at each atrial pacing CL starting at 240 ms decreasing by 10-ms increments. RAMAPD alternans was observed in 10 of 12 dogs at a CL of 163 +/- 17 ms before and in 10 of 12 dogs at s CL of 198 +/- 29 ms (p < 0.01) after rapid atrial pacing. Sustained atrial fibrillation (AF) (>5 minutes) was induced in 1 of 12 dogs at a pacing CL of 130 ms before rapid atrial pacing and in 4 of 12 dogs at a pacing CL of 135 +/- 17 ms after rapid atrial pacing. Onset of AF was always preceded by the RAMAPD alternans. Sixty minutes of rapid atrial pacing leads to diminution of rate adaptation of atrial action potential duration (APD) and appearance of APD alternans of greater magnitude at longer CL, both of which may contribute to the initiation and perpetuation of AF during its early phase.
authors.affiliation: The Second Department of Medicine, Nihon University School of Medicine, 30-1 Oyaguchi-kami, Itabashi-Ku, Tokyo 173-8610, Japan. iwatanab@med.nihon-u.ac.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Watanabe
authors.forename: Riko
authors.initials: R
authors.lastname: Masaki
authors.forename: Min
authors.initials: M
authors.lastname: Nuo
authors.forename: Naohiro
authors.initials: N
authors.lastname: Oshikawa
authors.forename: Kimie
authors.initials: K
authors.lastname: Okubo
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Okumura
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ohya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Saito
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Katsuo
authors.initials: K
authors.lastname: Kanmatsuse
mesh_terms: D000200:Action Potentials; D000818:Animals; D001281:Atrial Fibrillation / Q000209:etiology; D016275:Atrial Function / Q000502:physiology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004285:Dogs; D006325:Heart Atria; D013997:Time Factors