A Comparison of Chronaxies for Ventricular Fibrillation Induction, Defibrillation, and Cardiac Stimulation: Unexpected Findings and Their Implications

Lawo, Thomas; Deneke, Thomas; Schrader, Juergen; Danilovic, Dejan; Wenzel, Beate; Buddensiek, M.; Muegge, Andreas

doi:10.1111/j.1540-8167.2008.01319.x

Cited by 10 publications

(13 citation statements)

References 56 publications

(171 reference statements)

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“…A table of optimal pulse durations under the assumption of a chronaxie of 2 ms can be found in the above‐mentioned paper . Some studies have reported larger chronaxie values, but they considered the rheobase as a lower limit for the average current and not for the instantaneous current (or field) The rheobase field for myocardial cells is of the order of 60 V/m .…”

Section: Discussionmentioning

confidence: 99%

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

Irnich

Kroll

2015

Pacing Clinical Electrophis

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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...

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Section: Discussionmentioning

confidence: 99%

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

Irnich

Kroll

2015

Pacing Clinical Electrophis

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“…In this issue of the Journal , Lawo et al 47 . show experimental evidence that suggests that strength–duration curve may offer additional insights that seem to have been overlooked so far by old theories.…”

Section: Editorial Commentmentioning

confidence: 99%

Chronaxie of Defibrillation: A Pathway Toward Further Optimization of Defibrillation Waveform?

Efimov¹

2009

Cardiovasc electrophysiol

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“…Strength-duration curves were theoretically studied for optimizing ventricular defibrillation thresholds for both square-wave stimulation pulses and exponential discharge pulses and were shown to be ideally hyperbolic (Irnich 2008;Koning et al 1975). Experimental studies of strength-duration relationships were conducted, e.g., in the left ventricular epicardium of patients undergoing cardiac resynchronization therapy (Dhar et al 2009;Scally et al 2007), in the right ventricular apex for transvenous defibrillation in humans and in animal models, as well as in the atria and ventricles of patients with acutely implanted pacing leads (Coates and Thwaites 2000;Gold and Shorofsky 1997;Lawo et al 2009). …”

Section: Introductionmentioning

confidence: 98%

Subthreshold Parameters of Cardiac Tissue in a Bi-Layer Computer Model of Heart Failure

Zlochiver

2010

Cardiovasc Eng

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Current density threshold and liminal area are subthreshold parameters of the cardiac tissue that indicate its susceptibility to external and internal stimulations. Extensive experimental and theoretical research has been conducted to quantify these two parameters in normal conditions for both animal and human models. Here we employed a 2D numerical model of human cardiac tissue to assess these subthreshold parameters under the pathological conditions of heart failure and fibrosis. Stimuli were applied over an area ranging from 0.04 to 1 mm² using various pulse durations. The current density threshold decreased with increasing stimulation area or pulse duration. No significant changes were found in both parameters between control conditions and heart failure in the atrial tissue, while in the ventricular tissue, heart failure resulted in significantly reduced excitability with higher stimulation current magnitudes needed for excitation and larger liminal areas. This results from the specific ionic remodeling in ventricular heart failure that affects both subthreshold active currents such as I(K₁) and connexin 43 conductance. In fibrosis, increased fibroblast to myocyte coupling coefficient had a non-linear influence on current density thresholds, with an initial increase of current magnitude followed by a relaxation phase down to the current magnitude threshold for the control condition with no fibrosis. The results show that subthreshold excitation properties of the myocardium are influenced in a complex, non-linear manner by cardiac pathologies. Such observations may contribute to our understanding of impulse capturing properties, relevant, for example, for the generation of ectopic foci-originated arrhythmias and for the efficient design of cardiac stimulating electrodes.

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A Comparison of Chronaxies for Ventricular Fibrillation Induction, Defibrillation, and Cardiac Stimulation: Unexpected Findings and Their Implications

Cited by 10 publications

References 56 publications

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

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

Chronaxie of Defibrillation: A Pathway Toward Further Optimization of Defibrillation Waveform?

Subthreshold Parameters of Cardiac Tissue in a Bi-Layer Computer Model of Heart Failure

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