title: Mechanism of the suppression of repetitive atrial firing by isoproterenol--comparison with disopyramide.
abstract: To investigate whether isoproterenol (Iso) could suppress the initiation of repetitive atrial firing (RAF), we investigated its effect on RAF in comparison with that of disopyramide (Diso). Extrastimuli at a basic cycle length of 500 ms were delivered from the high right atrium in 49 patients who received an intravenous infusion of Iso (0.01 microgram/kg per min) and in 39 patients given intravenous Diso (2 mg/kg per 10 min). Induction of RAF, the atrial effective refractory period (A-ERP), and the maximum conduction delay (MCD) were measured. Iso abolished the induction of RAF in 13/19 (68%) patients, while Diso did so in 13/22 (59%) patients. Thirty-four of the 41 patients with RAF in the baseline study had an A-ERP < 250 ms and an MCD > 40 ms. Iso significantly decreased the A-ERP from 205 +/- 26 to 194 +/- 23 ms (P < 0.01) and significantly decreased the MCD from 67 +/- 24 to 39 +/- 16 ms (P < 0.0001) in 19 patients with RAF. On the other hand, Diso significantly increased the A-ERP from 203 +/- 31 to 235 +/- 36 ms (P < 0.0001), and significantly diminished the MCD from 68 +/- 31 to 55 +/- 30 ms (P < 0.01) in 22 patients with RAF. In patients with new RAF (n = 7) or re-induced RAF (n = 14) during Iso or after Diso, the MCD was more than 40 ms. Our results suggest that there are two different modes of RAF suppression, i.e. shortening or lengthening of the A-ERP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Third Department of Internal Medicine, Nagasaki University School of Medicine, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Shimizu
authors.forename: M
authors.initials: M
authors.lastname: Fukatani
authors.forename: M
authors.initials: M
authors.lastname: Tanigawa
authors.forename: M
authors.initials: M
authors.lastname: Kaibara
authors.forename: A
authors.initials: A
authors.lastname: Konoe
authors.forename: S
authors.initials: S
authors.lastname: Isomoto
authors.forename: O A
authors.initials: OA
authors.lastname: Centurion
authors.forename: K
authors.initials: K
authors.lastname: Yano
authors.forename: K
authors.initials: K
authors.lastname: Hashiba
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000503:physiopathology; D016275:Atrial Function / Q000187:drug effects* / Q000502:physiology; D004206:Disopyramide / Q000494:pharmacology* / Q000627:therapeutic use; D004558:Electric Stimulation; D004562:Electrocardiography; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology* / Q000627:therapeutic use; D008875:Middle Aged
chemical_list: D004206:Disopyramide; D007545:Isoproterenol