A Model of Electrostimulation Based on the Membrane Capacitance as Electromechanical Transducer for Pore Gating

Abstract

Results: The exogenous electric field must always be equal to or greater than the rheobase field strength (rheobase condition). This concept yields a final result that the voltage-pulse-content produced by the exogenous field between the two ends of a cell is a linear function of the pulse duration at threshold level. Thus, the model yields mathematical formulations that can describe and explain the characteristic features of electrostimulation. Conclusions: Our model of electrostimulation can describe and explain electrostimulation at cellular level. The model's predictions are consistent with published experimental studies. Practical applications in cardiology are discussed in the light of this model of electrostimulation. (PACE 2015; 38:831-845) electrostimulation, membrane capacitance, electromechanical transducer, rheobase, chronaxie, strength-duration relationship, rheobase condition, pore gating Introduction Electrostimulation has gained enormous importance in modern medicine. Implantable pacemakers and defibrillators, pain stimulators, and cochlear implants are obvious. Though electrostimulation has been studied for centuries, the theoretical background is still not completely understood.Most electrostimulation macromodels use the electrical current as the primary parameter to describe the conventional strength-duration Disclosures: Mark W. Kroll is an ad hoc speaker for St. Jude Medical. Werner Irnich: nothing to disclose. Address for reprints: Werner E. Irnich, PH.D., Faculty of Medicine, Justus-Liebig-University, Friedrichstr. 18, 35392 Giessen, Germany; This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.Received September 24, 2014; revised November 16, 2014; accepted December 12, 2014 accepted December 12, . doi: 10.1111 relationship. These models normally assume that the stimulation pulse charges up the passive cell membrane capacitance and then the increased (less-negative) transmembrane voltage activates voltage-gated sodium channels.Early in his career author Werner Irnich had the surprising finding that the threshold current was reduced considerably when the surface areas of pacemaker electrodes were reduced from 90 mm 2 to 30 mm 2 . 1 Existing current-based theory could not explain why the threshold was reduced when the diminished surface area increases the impedance to current flow. This experience led to four hypotheses:1. The current is a threshold parameter that is dependent on several characteristics such as electrode area and conductivity.2. The strength-duration relationship describes only the output characteristics of the stimulation generator. It does not express what happens at the cellular level.3. The strength-duration relationship offers no indication of how pulse shapes other than rectangular should be treated. 4. The strength-duration relationship advises to stimulate wi...