title: Mechanical characterization of rabbit pulmonary vein sleeves in in vitro intact ring preparation.
abstract: BACKGROUND
  Pulmonary vein (PV) sleeves, composed of cardiomyocytes, play certain roles in arrhythmogenesis. In the literature, it has been frequently reported that PV sleeves possess intrinsic spontaneous pacemaking activity and triggered activity in normal dogs and rabbits. In contrast, other research groups presented totally opposite findings which showed absence of such pacemakers in dogs, rabbits and rats. The present study was designed to clarify this puzzle and contradiction.
  
  
  METHODS
  A novel methodology using in vitro experimentation was used to examine the electromechanical activity of whole segments of PV sleeves. The ring preparation was composed of a small piece of left atrial (LA) free wall, PV ostium and sleeve from rabbits. A circumferential contraction of the PV sleeve was measured when the preparation was electrically driven from the LA free wall. Mechanical force of the ring preparation was measured using a force transducer. The action potentials were recorded using conventional intracellular recording technique in strip preparation.
  
  
  RESULTS
  In 15 rabbits, no spontaneous pacemaking activity or triggered activity was found in the in vitro ring preparation of PV sleeve. The circumferential contraction of PV sleeves was external calcium-dependent. Frequency-force relation displayed a negative staircase at 0.1-0.5 Hz and a positive staircase at 1-5 Hz. Post-rest potentiation was prominent between 15 s and 120 s. Intracellular action potential recording did not display any automaticity or triggered activity in PV sleeves.
  
  
  CONCLUSIONS
  In an intact ring preparation of rabbit PV sleeves, intrinsic spontaneous pacemaking activity or triggered activity was not found.
authors.affiliation: Department of Anesthesiology, Taichung Veterans General Hospital, Providence University, Taichung, Taiwan, ROC. luk1015@vghtc.gov.tw
authors.forename: Hsiang-Ning
authors.initials: HN
authors.lastname: Luk
authors.forename: Chu-Pin
authors.initials: CP
authors.lastname: Lo
authors.forename: Hui-Chun
authors.initials: HC
authors.lastname: Tien
authors.forename: Daniel
authors.initials: D
authors.lastname: Lee
authors.forename: Zong-Li
authors.initials: ZL
authors.lastname: Chen
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Shih-Tai
authors.initials: ST
authors.lastname: Hsin
authors.forename: Yuan-Ji
authors.initials: YJ
authors.lastname: Day
mesh_terms: D000200:Action Potentials; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology; D016477:Artifacts; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D011667:Pulmonary Veins / Q000502:physiology*; D011817:Rabbits; D014661:Vasoconstriction
chemical_list: D002118:Calcium