Theoretical and experimental study of sawtooth effect in isolated cardiac cell-pairs

Authors
Citation
V. Sharma et L. Tung, Theoretical and experimental study of sawtooth effect in isolated cardiac cell-pairs, J CARD ELEC, 12(10), 2001, pp. 1164-1173
Citations number
57
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Journal title
JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY
ISSN journal
1045-3873 → ACNP
Volume
12
Issue
10
Year of publication
2001
Pages
1164 - 1173
Database
ISI
SICI code
1045-3873(200110)12:10<1164:TAESOS>2.0.ZU;2-W
Abstract
Sawtooth Effect in Cell-Pairs. Introduction: The question of how a defibril lation shock affects the myocardium far (> similar to1 mm; the space consta nt of continuum tissue models) from the electrode is not fully understood. According to a long-standing, yet to be verified, hypothesis, the relativel y high-resistance intercellular gap junctions may help in coupling the shoc k effect to the distant myocardium by redistributing the defibrillation cur rent and creating a sawtooth pattern of polarization in which every cell un dergoes hyperpolarization and depolarization. The goal of this study was to conduct an in-depth theoretical and experimental investigation of the sawt ooth effect in the simplest coupled system, that of an isolated cell-pair. Methods and Results : Theoretically, we present a relationship between sawt ooth amplitude (STA) and junctional resistance (R-j), and show that, in a c ell-pair with two cells of different lengths, the sawtooth effect may not n ecessarily appear as a reversal in polarization across the junction when Rj is below a critical value. Experimentally, we optically mapped transmembra ne potential responses along the lengths of enzymatically isolated guinea p ig cell-pairs at 10- or 17-mum resolution, and estimated STA as the magnitu de of discontinuity in responses at the intercellular junction. From 14 cel l-pairs, STA was estimated to be similar to 11 mV for a nominal 10 V/cm fie ld. Based on our theoretical results, this value corresponds to an R-j of s imilar to 18 M Omega. Conclusion: The intercellular junction induces a measurable sawtooth effect in the simplest system of an isolated cell-pair. An accounting for the saw tooth effect might be essential for understanding field-tissue interaction far from the electrode and to accurately predict tissue response during fie ld stimulation.