Mechanical characterization of rabbit pulmonary vein sleeves in in vitro intact ring preparation.
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.
Luk
Hsiang-Ning
HN
Department of Anesthesiology, Taichung Veterans General Hospital, Providence University, Taichung, Taiwan, ROC. luk1015@vghtc.gov.tw
Lo
Chu-Pin
CP
Tien
Hui-Chun
HC
Lee
Daniel
D
Chen
Zong-Li
ZL
Wang
Fei
F
Hsin
Shih-Tai
ST
Day
Yuan-Ji
YJ
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
D002118:Calcium