TY - JOUR
T1 - Effects of the tissue-bath interface on the induced transmembrane potential
T2 - A modeling study in cardiac stimulation
AU - Trayanova, Natalia A.
N1 - Funding Information:
In cardiac stimulation and defibrillation, the distribution of transmembrane potential generated in cardiac tissue by a strong external stimulus depends on: (i) the induced initial membrane polarization that is the result of the interaction between tissue structure and the exogenous current that traverses it, and (ii) the subsequent extension of refractoriness and generation of wavefronts evoked by this membrane polarization. The latter aspect of this process has been targeted by the majority of stimulation/ Acknowledgment--The author thanks Lisa Malden for running part of the simulations and for her aid in the preparation of the figures. This work was supported by National Science Foundation/Engineering Research Center Grant CDR-8622201. Address correspondence to Natalia A. Trayanova, Department of Biomedical Engineering, Tulane University, New Orleans, LA 70118. (Received 18Ju196, Revised 18Feb97, Revised 14Mar97, Accepted 21Mar97) defibrillation research effort for many years (see Refs. 5 and 6 for review). Unraveling the mechanisms of the membrane processes after a strong stimulus or defibrillation shock requires first, however, to obtain knowledge of how initial change in transmembrane potential is established by the interaction of applied electrical current with cardiac tissue structure. Recent theoretical models (15,19,21) and experimental studies (10,12,13,24,26) have brought new insight into the spatial distribution of membrane polarization in cardiac tissue during the initial phase of electrical stimulation/ defibrillation. Modeling studies using the bidomain model (for a review on the bidomain model, see Ref. 12) have predicted that the membrane is hyperpolarized or depolarized throughout regions that comprise many cardiac cells. A conclusion was derived from these studies (18,20) that the pattern of transmembrane potential distribution is highly dependent on: (i) the relative degree of anisotrophy in the bulk electrical properties of the inside of all fibers (including both myoplasm and intracellular junctions) and of the interstitium, often referred to as the "anisotrophy ratios"; and (ii) the applied electric field and its change with position along the fiber pathways. However, the model tissue preparations considered in these simulations were either of infinite extent (15,16) or had insulating boundaries (19). We envision that the pattern of transmembrane potential established during the initial phase of electrical stimulation of cardiac tissue will be altered when the tissue is in contact with a low-resistance volume conductor. The blood is the natural volume conductor that bathes the myocardium. In addition, experimental measurements of the transmembrane potential induced by the defibrillation shock often use preparations that are imbedded in a perfuseate (8-11,13). Understanding of the pattern of shock-induced polarization in the heart and correct interpretation of measured potentials requires a knowledge of the influence of the volume conductor surrounding the tissue on the electrical response of the myocardium to an exogenous stimulus. Thus, the objective of the present research is to examine the role of the volume conductor bordering the myocardium in establishing the distribution of stimulus-induced membrane polarization in the tissue. We hypoth-
PY - 1997
Y1 - 1997
N2 - During the initial stages of cardiac stimulation or defibrillation, the distribution of transmembrane potential generated in the myocardium by the external stimulus is determined by the local interactions between fibrous tissue organization and applied electric field. We hypothesize that the pattern of induced transmembrane potential is different, depending on whether the tissue is in insulator, such as air, or in contact with a low-resistance volume conductor, such as blood or perfuseate. The goal of this study is to evaluate the impact of the volume conductor bordering the myocardium on the pattern of stimulusinduced transmembrane potential. Presented here are computer simulations of the steady-state response of model tissue-bath preparations to extracellular current stimuli. Transmembrane potential distributions for various tissue and bath sizes, as well as locations of the stimulation electrodes, are examined. The results indicate that when the external stimuli are located in close proximity to or at the tissue-bath interface, both the magnitude and the distribution of transmembrane potential are significantly altered, compared with the case of an insulated preparation. Thus, the volume conductor seems to be another possible factor contributing to the pattern of membrane hyper- and depolarization in the myocardium. Its influence is, however, modulated by the promixity of the stimuli sites to the tissue-bath interface.
AB - During the initial stages of cardiac stimulation or defibrillation, the distribution of transmembrane potential generated in the myocardium by the external stimulus is determined by the local interactions between fibrous tissue organization and applied electric field. We hypothesize that the pattern of induced transmembrane potential is different, depending on whether the tissue is in insulator, such as air, or in contact with a low-resistance volume conductor, such as blood or perfuseate. The goal of this study is to evaluate the impact of the volume conductor bordering the myocardium on the pattern of stimulusinduced transmembrane potential. Presented here are computer simulations of the steady-state response of model tissue-bath preparations to extracellular current stimuli. Transmembrane potential distributions for various tissue and bath sizes, as well as locations of the stimulation electrodes, are examined. The results indicate that when the external stimuli are located in close proximity to or at the tissue-bath interface, both the magnitude and the distribution of transmembrane potential are significantly altered, compared with the case of an insulated preparation. Thus, the volume conductor seems to be another possible factor contributing to the pattern of membrane hyper- and depolarization in the myocardium. Its influence is, however, modulated by the promixity of the stimuli sites to the tissue-bath interface.
KW - Cardiac stimulation
KW - Computer simulations
KW - Transmembrane potential
KW - Volume conductor
UR - https://www.scopus.com/pages/publications/0031239816
UR - https://www.scopus.com/pages/publications/0031239816#tab=citedBy
U2 - 10.1007/BF02684162
DO - 10.1007/BF02684162
M3 - Article
C2 - 9300102
AN - SCOPUS:0031239816
SN - 0090-6964
VL - 25
SP - 783
EP - 792
JO - Annals of biomedical engineering
JF - Annals of biomedical engineering
IS - 5
ER -