title: In vivo recording of Zhang's phenomenon (His electrogram alternans): a novel index of atrioventricular node dual pathway conduction.
abstract: BACKGROUND
  Zhang's phenomenon (originally His electrogram alternans) is a new index of atrioventricular node dual pathway electrophysiology. This index has been described and validated in isolated hearts in vitro, but has not been recorded in vivo.
  
  
  METHODS
  This study explored the feasibility of in vivo recording of Zhang's phenomenon (His electrogram alternans) in six dogs with a custom-built bipolar electrode.
  
  
  RESULTS
  The His electrogram recorded from superior His bundle domain (superior His electrogram) was high in amplitude at basic beats and long coupling intervals (i.e., fast pathway conduction) and low amplitude at short prematurities (i.e., slow pathway conduction). In contrast, His electrogram recorded from the inferior His bundle domain (inferior His electrogram) was always from low amplitude during fast pathway conduction to high amplitude during slow pathway conduction. The characteristic His electrogram alternans had been recorded in vivo in all six animals.
  
  
  CONCLUSIONS
  This study provided the first data representing in vivo recording of Zhang's phenomenon (His electrogram alternans) in large animals. Clinical studies are needed before this novel index can be applied in patients.
authors.affiliation: Departments of Cardiovascular Medicine and Molecular Cardiology, The Cleveland Clinic Foundation, Cleveland, OH, USA, yzhang49@nyit.edu.
authors.forename: Youhua
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001283:Atrioventricular Node / Q000502:physiology*; D002036:Bundle of His / Q000502:physiology*; D004285:Dogs; D004562:Electrocardiography / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D006801:Humans; D009431:Neural Conduction / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D012720:Severity of Illness Index