title: Atrial remodeling and the substrate for atrial fibrillation in rat hearts with elevated afterload.
abstract: BACKGROUND
  Although arterial hypertension and left ventricular hypertrophy are considered good epidemiological indicators of the risk of atrial fibrillation (AF) in patients, the link between elevated afterload and AF remains unclear. We investigated atrial remodeling and the substrate for arrhythmia in a surgical model of elevated afterload in rats.
  
  
  RESULTS
  Male Wistar rats (aged 3-4 weeks) were anesthetized and subjected to either partial stenosis of the ascending aorta (AoB) or sham operation (Sham). Experiments were performed on excised hearts 8, 14, and 20 weeks after surgery. Unipolar electrograms were recorded from the left atrial epicardial surface of perfused hearts using a 5×5 electrode array. Cryosections of left atrial tissue were retained for histological and immunocytochemical analyses. Compared to Sham, AoB hearts showed marked left atrial hypertrophy and fibrosis at 14 and 20 weeks postsurgery. The incidence and duration of pacing-induced AF was increased in hearts from AoB rats at 20 weeks postsurgery. The substrate for arrhythmia was associated with reduced vectorial conduction velocity and greater inhomogeneity in conduction but without changes in effective refractory period. Left atrial expression of the gap junction protein, connexin43, was markedly reduced in AoB compared with Sham hearts.
  
  
  CONCLUSIONS
  Using a small-animal model, we demonstrate that elevated afterload in the absence of systemic hypertension results in increased inducibility of AF and left atrial remodeling involving fibrosis, altered atrial connexin43 expression, and marked conduction abnormalities.
authors.affiliation: Cardiovascular Research Laboratories, School of Physiology & Pharmacology, University of Bristol, Bristol, UK.
authors.forename: Shang-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Stéphanie C M
authors.initials: SC
authors.lastname: Choisy
authors.forename: Palash
authors.initials: P
authors.lastname: Barman
authors.forename: Haifei
authors.initials: H
authors.lastname: Zhang
authors.forename: Jules C
authors.initials: JC
authors.lastname: Hancox
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Jones
authors.forename: Andrew F
authors.initials: AF
authors.lastname: James
mesh_terms: D000818:Animals; D001024:Aortic Valve Stenosis / Q000150:complications / Q000503:physiopathology*; D001281:Atrial Fibrillation / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D018031:Connexin 43 / Q000378:metabolism; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D005355:Fibrosis; D017629:Gap Junctions / Q000502:physiology; D006325:Heart Atria / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology; D006984:Hypertrophy / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D017379:Hypertrophy, Left Ventricular / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018031:Connexin 43