Electrical constants of arterially perfused rabbit papillary muscle.

Kléber, André G.; Riegger, Christoph

doi:10.1113/jphysiol.1987.sp016495

Cited by 170 publications

(88 citation statements)

References 24 publications

(47 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such differences can be explained by the classic cable theory, according to which the ⌬V m magnitude rapidly decays and the time constant increases with the distance from the tissue-bath interface. 5 Therefore, depth signal averaging should produce smaller and slower ⌬V m in GS tissue than SS tissue, which corresponds to the present observations. During stronger shocks, profound differences in the shape of SS and GS responses were found.…”

Section: Intramural Virtual Electrodessupporting

confidence: 55%

Intramural Virtual Electrodes in Ventricular Wall

Sharifov

Fast

2004

Circulation

View full text Add to dashboard Cite

Background-Intramural virtual electrodes (IVEs) are believed to play an important role in defibrillation, but their existence in intact myocardium remains unproven. Here, IVEs were detected by use of optical recordings of shock-induced transmembrane potential (V m ) changes (⌬V m ) measured from the intact epicardial heart surface. Methods and Results-To detect IVEs, isolated porcine left ventricles were sequentially stained with a V m -sensitive dye by 2 methods: (1) surface staining (SS) and (2) global staining (GS) via coronary perfusion. Shocks (2 to 50 V/cm) were applied across the ventricular wall in an epicardial-to-endocardial direction during the action potential plateau via transparent mesh electrodes, and shock-induced ⌬V m were measured optically from the same epicardial locations after SS and GS. Optical recordings revealed significant differences between ⌬V m of 2 types that became more prominent with increasing shock strength: (1) for weak shocks, SS-⌬V m were larger and faster than GS-⌬V m ; (2) for intermediate shocks, cathodal GS-⌬V m became multiphasic, whereas SS-⌬V m remained monophasic; and (3) for strong shocks, cathodal GS-⌬V m became uniformly negative, whereas SS-⌬V m typically remained positive. The radical differences in the shape and polarity of SS and GS polarizations can be explained by the contribution of subepicardial IVEs to optical signals. Histological examination revealed a dense network of collagen septa in the subepicardium, which could form the IVE substrate. Conclusions-Intramural virtual electrodes are reflected in optical measurements of shock-induced ⌬V m on the intact epicardial surface. These IVEs could be a result of microscopic resistive discontinuities formed by collagen septa.

show abstract

Section: Intramural Virtual Electrodessupporting

confidence: 55%

Intramural Virtual Electrodes in Ventricular Wall

Sharifov

Fast

2004

Circulation

View full text Add to dashboard Cite

show abstract

“…Several factors may be taken into account to explain this discrepancy. Firstly, the intracellular longitudinal resistivity of Purkinje fibers has been reported to be lower than in the working myocardium [34,40,41]. According to our simulations (Fig.…”

Section: Estimation Of Critical Strand Width In Ventricular Tissue Anmentioning

confidence: 80%

Block of impulse propagation at an abrupt tissue expansion: evaluation of the critical strand diameter in 2- and 3-dimensional computer models

FAST¹

1995

Cardiovascular Research

View full text Add to dashboard Cite

. ___ .-_---_----Objective: Unidirectional conduction block in the heart can occur at a site where the impulse is transmitted from a small to a large tissue volume. The aim of this study was to evaluate the occurrence of conduction block in a 2-dimensional and 3-dimensional computer model of cardiac tissue consisting of a narrow strand abruptly emerging into a large area. In this structure, the strand diameter critical for the occurrence of block, h,, was evaluated as a function of changes in the active and passive electrical properties of both the strand and the large medium. M&hods: The effects of changes in the following parameters on h, were analysed: (I 1 maximum sodium conductance (gNa,,, 1, (21 longitudinal (R,) and transverse (R,) intracellular resistivities, and (3) inhomogeneities in gNa,,,, and R, and R," between the strand and the large area. Three ionic models for cardiac excitation described by Beeler-Reuter, Ebihara-Johnson, andLuo-Rudy ionic current kinetics were compared. Results: In the 2-dimensional simulations, h, was 175 pm in Ebihara-Johnson and Beeler-Reuter models and 200 pm in the Luo-Rudy model. At the critical strand diameter, the site of conduction block was located beyond the transition, i.e. a small circular area was activated in the large medium, whereas with narrower strands conduction block occurred within the strands. The decrease of gNa,,, resulted in a large increase of h,. This increase was mainly due to the change of d%7l,x in the large area, while h, was almost independent of giva,,, in the strand. Changing R, had no effect on h,, whereas the increase of R, decreased h, and reversed conduction block. Inhomogeneous changes of R, and R, in the strand versus the large medium had opposite effects on h,. When the resistivities of the strand alone were increased, h, also increased. In contrast, the increase of the resistivities in the large area reduced h,. In the 3-dimensional model, h, was 2.7 times larger than the corresponding Sdimensional values at the various levels of gNa,,, and resistivity. Conclusions: (1) At physiological values for active and passive electrical properties, h, in the 2D simulations is close to 200 pm in all three ionic models. In the 3-dimensional simulations, I?, is 2.7 larger than in the 2-dimensional models. (2) The excitable properties of the large area but not of the strand modify h,.. The decrease of intercellular coupling in the large medium facilitates impulse conduction and reduces h,., while the same change in the strand increases h,.. (3) Occurrence of conduction block at an abrupt geometrical transition can be explained by both the impedance mismatch at the transition site and the critical curvature beyond the transition.

show abstract

“…The time elapsed between cross-clamping the aorta and perfusion was Ͻ5 minutes. Once perfused, the septum was secured in a Lexan chamber 7 and perfused with the previous perfusate supplemented with bovine erythrocytes delivered by a peristaltic pump. The hematocrit level was 0.40.…”

mentioning

confidence: 99%

Electrical Properties and Conduction in Reperfused Papillary Muscle

Cascio

Yang

Johnson

et al. 2001

Circulation Research

View full text Add to dashboard Cite

Abstract-The reversibility of ischemia-induced changes of extracellular K ϩ concentration ([K ϩ ] o ), resting membrane potential (E M ), and passive cable-like properties, ie, extracellular resistance and cell-to-cell electrical coupling, and their relationship to recovery of conduction and contraction is described in 25 reperfused rabbit papillary muscles. No-flow ischemia caused extracellular K ϩ accumulation, depolarization of E M , an increase in whole-tissue (r t ), external (r o ), and internal (r i ) longitudinal resistances, and failure of conduction and contraction. Muscles were reperfused 10 minutes after the onset of ischemia related cell-to-cell electrical uncoupling, ie, 26Ϯ1 minutes after arrest of perfusion. In 11 muscles, incomplete reflow occurred with only partial recovery of [K ϩ ] o and r t . In the remaining 14 muscles, reperfusion caused a rapid and parallel decrease in [K ϩ ] o , r t , and r o . When complete tissue reperfusion occurred, cell-to-cell electrical uncoupling was largely reversible. Thus, cell-to-cell electrical uncoupling did not indicate irreversible injury. Reperfusion induced a depolarizing current widening the difference between the K ϩ equilibrium potential and the E M . This difference decreased after longer periods of reperfusion. Conduction was restored and conduction velocity approached preischemic values as cell-to-cell electrical interaction was reestablished and E M recovered. The recovery of r o preceded r i , decreasing the ratio of the extracellular to intracellular resistance early in reperfusion, an effect predicted to influence the amplitude of the extracellular voltage field and electrocardiographic ST segments during reperfusion. (Circ Res. 2001;89:807-814.)

show abstract

Electrical constants of arterially perfused rabbit papillary muscle.

Cited by 170 publications

References 24 publications

Intramural Virtual Electrodes in Ventricular Wall

Intramural Virtual Electrodes in Ventricular Wall

Block of impulse propagation at an abrupt tissue expansion: evaluation of the critical strand diameter in 2- and 3-dimensional computer models

Electrical Properties and Conduction in Reperfused Papillary Muscle

Contact Info

Product

Resources

About