title: Heterogeneous pulmonary vein myocardial cell repolarization implications for reentry and triggered activity.
abstract: BACKGROUND
  Myocardial cells in the pulmonary veins (PVs) are thought to play a major role in the initiation and maintenance of atrial arrhythmias, including atrial fibrillation. However, systematic single-cell microelectrode recordings from different regions in intact PV-atrial tissues are lacking.
  
  
  OBJECTIVE
  The purpose of this study was to determine the transmembrane action potential properties of myocardial cells in different regions of the PV and the left atrium (LA) and assess their arrhythmogenic potential during perfusion with isoproterenol (ISO) and rapid atrial pacing.
  
  
  METHODS
  Glass microelectrode recordings of action potentials were made from the left PV and the LA in Langendorff-perfused young (3-4 month) male rats (Fisher344) (n = 9).
  
  
  RESULTS
  Action potential duration (APD) of atrial and PV cells had similar duration at a pacing cycle length (CL) of 200 ms. However, shortening of the pacing CL to 100 ms led to heterogeneous repolarization of PV cells. Mid-PV cells had a significantly higher maximum slope of APD restitution than atrial or other PV sites. Intra-PV conduction block developed at rates when LA and proximal PV cells manifested 1:1 capture. Perfusion of ISO and rapid atrial pacing promoted the emergence of early afterdepolarization (EAD) and triggered beats in two out of nine tissues, causing premature atrial activation. No difference in resting potential or AP amplitude could be detected among the PV and LA cells.
  
  
  CONCLUSIONS
  PV myocardial cells develop marked heterogeneity in repolarization, and there is a slight ease of developing EAD and triggered activity in response to rapid pacing and ISO infusion.
authors.affiliation: Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Mizuho
authors.initials: M
authors.lastname: Miyauchi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Okuyama
authors.forename: William J
authors.initials: WJ
authors.lastname: Mandel
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
authors.forename: Hrayr S
authors.initials: HS
authors.lastname: Karagueuzian
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D016275:Atrial Function / Q000502:physiology*; D002304:Cardiac Pacing, Artificial; D006325:Heart Atria / Q000166:cytology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D032383:Myocytes, Cardiac / Q000502:physiology*; D010477:Perfusion; D011667:Pulmonary Veins / Q000166:cytology / Q000503:physiopathology*; D051381:Rats; D011916:Rats, Inbred F344; D013566:Sympathomimetics / Q000494:pharmacology
chemical_list: D013566:Sympathomimetics; D007545:Isoproterenol