title: Activation pattern of the avian left ventricle during ventricular pacing.
abstract: OBJECTIVE
  This study was planned to investigate ventricular myocardial excitation in birds in which Purkinje fibres penetrate into the ventricular wall and reach the epicardium to advance our knowledge about the evolution of the ventricular activation process in vertebrates.
  
  
  METHODS
  A depolarization pattern of the left ventricular free wall in seven open-chest laying hens was mapped by 14 seven-electrode plunge needles under ventricular pacing from different sites.
  
  
  RESULTS
  Duration of activation of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm. Its lowest increase occurs during subendocardial pacing of the middle part of the left ventricle, but its greatest increase is observed during subepicardial pacing of the left ventricular base. Multifocality and mosaicity of depolarization of the left ventricular myocardium are expressed in a considerably less degree during ventricular pacing in comparison with sinus rhythm.
  
  
  CONCLUSIONS
  Ectopic excitation of avian heart ventricles occurs mostly due to successive spreading of the activation wave from a pacing site during both ipsi- and contraventricular pacing. During ipsiventricular pacing at least, ectopic excitation of the heart ventricles with the "rich" Purkinje network behaves like one of the mammalian ventricles with the subendocardial Purkinje network.
authors.affiliation: Laboratory of Cardiac Physiology, Institute of Physiology of the Komi Science Centre, Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia. s.kharin@physiol.komisc.ru
authors.forename: Sergey
authors.initials: S
authors.lastname: Kharin
authors.forename: Nadezhda
authors.initials: N
authors.lastname: Antonova
authors.forename: Dmitry
authors.initials: D
authors.lastname: Shmakov
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D002645:Chickens / Q000502:physiology*; D005260:Female; D006329:Heart Conduction System; D010496:Pericardium / Q000033:anatomy & histology; D011690:Purkinje Fibers / Q000033:anatomy & histology; D016276:Ventricular Function