title: Structural changes in the progression of atrial fibrillation: potential role of glycogen and fibrosis as perpetuating factors.
abstract: BACKGROUND
  Previous studies of the goat heart subjected to prolonged atrial pacing induced sustained atrial fibrillation (AF). Structural changes included marked accumulation of glycogen in atrial myocytes.
  
  
  OBJECTIVE
  In the present study, we hypothesized that glycogen deposition in canine atrial myocytes promotes paroxysmal forms of AF and is involved in fibrosis development in the later stages of AF.
  
  
  METHODS
  In dogs under pentobarbital anesthesia, tissues were obtained from the right and left atrial appendages (LAA/RAA). Periodic acid Schiff (PAS) and Masson's trichrome staining of the LAA/RAA from normal dogs, and those subjected to atrial pacing induced AF for 48 h or 8 weeks determined glycogen and collagen concentrations, respectively, using morphometric analysis.
  
  
  RESULTS
  At baseline, there was a significant greater concentration of glycogen in the LAA than the RAA (P ≤ 0.05). Compared to the RAA, the LAA glycogen, was dense and locked against the intercalated discs. After pacing induced AF for 48 hours and 8 weeks there was a marked increase in glycogen deposition, significantly greater than in the baseline state (P ≤ 0.05). There was a similar and progressive increase in collagen concentrations in each group (P ≤ 0.05).
  
  
  CONCLUSIONS
  The differential in glycogen concentration, in conjunction with other factors, neural and electrophysiological, provide a basis for the greater propensity of the left atrium for paroxysmal AF, at baseline and 48 hours of pacing induced AF. The marked increase in collagen at 8 weeks of pacing provides a substrate for sustained AF. Evidence is presented linking glycogen accumulation and fibrosis as factors in the persistent forms of AF.
authors.affiliation: Arrhythmia Research Lab, First Affiliated Hospital of Xinjiang Medical University Urumqi, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, Renmin Hospital of Wuhan University Wuhan, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Huang
authors.affiliation: Heart Rhythm Institute, University of Oklahoma Health Sciences Center Oklahoma City, Oklahoma, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Scherlag
authors.affiliation: Center for Veterinary Health Sciences, Oklahoma State University Stillwater, Oklahoma, USA.
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Ritchey
authors.affiliation: 13442 SW 102 Lane Miami, Florida, USA.
authors.forename: Abraham A
authors.initials: AA
authors.lastname: Embi
authors.affiliation: Department of Cardiovascular Diseases, Zhongshan Hospital Fudan University Shanghai, China.
authors.forename: Jialu
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Cardiovascular Diseases, The 6th People's Hospital affiliated to Shanghai Jiaotong University Shanghai, China.
authors.forename: Yuemei
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Heart Rhythm Institute, University of Oklahoma Health Sciences Center Oklahoma City, Oklahoma, USA.
authors.forename: Sunny S
authors.initials: SS
authors.lastname: Po
mesh_terms: D000818:Animals; D020517:Atrial Appendage / Q000473:pathology*; D001281:Atrial Fibrillation / Q000473:pathology*; D018450:Disease Progression; D004285:Dogs; D005260:Female; D005355:Fibrosis; D006003:Glycogen / Q000032:analysis / Q000378:metabolism*; D006325:Heart Atria / Q000473:pathology; D007091:Image Processing, Computer-Assisted; D008297:Male
chemical_list: D006003:Glycogen
keywords: Atrial fibrillation; fibrosis; glycogen