title: Effects of pre- and postconditioning on arrhythmogenesis in the in vivo rat model.
abstract: The antiarrhythmic potential of postconditioning in in vivo models remains poorly defined. We compared the effects of pre- and postconditioning on ventricular arrhythmogenesis against controls with and without reperfusion. Wistar rats (n = 40, 269 ± 3 g) subjected to ischemia (30 minutes)--reperfusion (24 hours) were assigned to the following groups: (1) preconditioning (2 cycles), (2) postconditioning (6 cycles), or (3) no intervention and were compared with (4) nonreperfused infarcts and (5) sham-operated animals. Infarct size was measured, and arrhythmogenesis was evaluated with continuous telemetric electrocardiographic recording, heart rate variability indices, and monophasic action potentials (MAPs). During a 24-hour observation period, no differences in mortality were observed. Reperfusion decreased infarct size and ameliorated sympathetic activation during the late reperfusion phase. Preconditioning decreased infarct size by a further 35% (P = .0017), but only a marginal decrease (by 18%, P = .075) was noted after postconditioning. Preconditioning decreased arrhythmias during ischemia and early reperfusion, whereas postconditioning almost abolished them during the entire reperfusion period. No differences were noted in MAPs or in the magnitude of sympathetic activation between the 2 interventions. Compared to postconditioning, preconditioning affords more powerful cytoprotection, but both interventions exert antiarrhythmic actions. In the latter, these are mainly evident during the ischemic phase and continue during early reperfusion. Postconditioning markedly decreases reperfusion arrhythmias during a prolonged observation period. The mechanisms underlying the antiarrhythmic effects of pre- and postconditioning are likely different but remain elusive.
authors.affiliation: Medical School, University of Ioannina, Ioannina, Greece. thkolet@cc.uoi.gr
authors.forename: Theofilos M
authors.initials: TM
authors.lastname: Kolettis
authors.forename: Agapi D
authors.initials: AD
authors.lastname: Vilaeti
authors.forename: Dimitrios G
authors.initials: DG
authors.lastname: Tsalikakis
authors.forename: Anastasia
authors.initials: A
authors.lastname: Zoga
authors.forename: Mesele
authors.initials: M
authors.lastname: Valenti
authors.forename: Alexandros T
authors.initials: AT
authors.lastname: Tzallas
authors.forename: Apostolos
authors.initials: A
authors.lastname: Papalois
authors.forename: Efstathios K
authors.initials: EK
authors.lastname: Iliodromitis
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000401:mortality / Q000503:physiopathology* / Q000517:prevention & control*; D004195:Disease Models, Animal; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D057775:Ischemic Postconditioning; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury; D051381:Rats; D017208:Rats, Wistar
keywords: arrhythmia; cytoprotection; postconditioning; preconditioning