title: Effects of central sympathetic activation on repolarization-dispersion during short-term myocardial ischemia in anesthetized rats.
abstract: OBJECTIVE
  Sympathetic activation during myocardial ischemia enhances arrhythmogenesis, but the underlying pathophysiologic mechanisms remain unclear. We investigated the central sympathetic effects on ventricular repolarization during the early-period post-coronary artery occlusion.
  
  
  METHODS
  We studied 12 Wistar rats (254±2 g) for 30 min following left coronary artery ligation, with (n=6) or without (n=6) pretreatment with the central sympatholytic agent clonidine. Mapping of left and right ventricular epicardial electrograms was performed with a 32-electrode array. As an index of sympathetic activation, heart rate variability in the frequency domain was calculated. Heart rate and repolarization duration were measured with a custom-made recording and analysis software, followed by calculation of intra- and inter-ventricular dispersion of repolarization.
  
  
  RESULTS
  Heart rate and heart rate variability indicated lower sympathetic activation in clonidine-treated rats during ischemia. Repolarization duration in the left ventricle prolonged after clonidine at baseline, independently of heart rate, but no differences were present 30 min post-ligation. Dispersion of repolarization in the right ventricle remained stable during ischemia, whereas it increased in the left ventricle, equally in both groups. A similar trend was observed for inter-ventricular dispersion, without differences between groups.
  
  
  CONCLUSIONS
  In addition to intra-ventricular repolarization-dispersion, anterior-wall myocardial ischemia may also increase inter-ventricular repolarization-dispersion. Progressive central sympathetic activation occurs during myocardial ischemia, but it does not affect intra- or inter-ventricular dispersion of ventricular repolarization during the early phase. Further research is warranted on the potential effects during subsequent time-periods.
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece. Electronic address: theofilos.m.kolettis@gmail.com.
authors.forename: Theofilos M
authors.initials: TM
authors.lastname: Kolettis
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece.
authors.forename: Vassilios
authors.initials: V
authors.lastname: La Rocca
authors.affiliation: Experimental Research Center ELPEN, Pikermi, Athens, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Psychalakis
authors.affiliation: Experimental Research Center ELPEN, Pikermi, Athens, Greece.
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Karampela
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece.
authors.forename: Marianthi
authors.initials: M
authors.lastname: Kontonika
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Tourmousoglou
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece.
authors.forename: Giannis G
authors.initials: GG
authors.lastname: Baltogiannis
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece; Experimental Research Center ELPEN, Pikermi, Athens, Greece.
authors.forename: Apostolos
authors.initials: A
authors.lastname: Papalois
authors.affiliation: Cardiovascular Research Institute, Ioannina and Athens, Greece.
authors.forename: Zenon S
authors.initials: ZS
authors.lastname: Kyriakides
mesh_terms: D000758:Anesthesia; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004562:Electrocardiography / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D008026:Ligation; D008297:Male; D017202:Myocardial Ischemia / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013565:Sympatholytics / Q000494:pharmacology; D016277:Ventricular Function, Left / Q000187:drug effects; D016278:Ventricular Function, Right / Q000187:drug effects
chemical_list: D013565:Sympatholytics; D003000:Clonidine
keywords: Central sympathetic activation; Myocardial ischemia; Repolarization-dispersion; Ventricular repolarization