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Wanda Krassowska Neu

Professor Emeritus of Biomedical Engineering
Biomedical Engineering
Box 90281, Durham, NC 27708-0281
Room 1427, Fitzpatrick Center (Fciemas), 101 Science Drive, Durham, NC 27708-0281

Selected Publications


Feasibility of non-invasive determination of the stability of propagation reserve in patients

Journal Article Computing in Cardiology · December 1, 2012 This study investigates the feasibility of using surface ECG recordings to assess stability of cardiac propagation. Our novel method customizes a reaction-diffusion model of cardiac excitation using measurements of patient's repolarization dynamics. The cu ... Cite

Asymptotic model of electrical stimulation of nerve fibers.

Journal Article Medical & biological engineering & computing · March 2012 We present a novel theory and computational algorithm for modeling electrical stimulation of nerve fibers in three dimensions. Our approach uses singular perturbation to separate the full 3D boundary value problem into a set of 2D "transverse" problems cou ... Full text Cite

Theory of electroporation

Journal Article · December 1, 2009 Experiments conducted on artificial bilayers, suspensions of vesicles or cells, and tissues have demonstrated that a large, externally induced transmembrane potential (V m) causes an increase in the conductivity of the membrane by five to six orders of mag ... Full text Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · December 1, 2009 Traditionally, it was believed that cardiac rhythm stability was governed by the slope of the restitution curve (RC), which relates the duration of an action potential to the preceding diastolic interval. However, a single RC does not exist; rate-dependenc ... Cite

Activating function of needle electrodes in anisotropic tissue

Journal Article Med. Biol. Eng. Comput. · 2009 Cite

Variability of action potential duration in pharmacologically induced long QT syndrome type 1.

Journal Article Annu Int Conf IEEE Eng Med Biol Soc · 2009 Long QT Syndrome (LQTS) is a congenital disorder associated with life-threatening arrhythmias. LQT1, a type of LQTS affecting the slow delayed rectifier potassium current, shows a higher incidence of arrhythmia associated with sympathetic stimulation than ... Full text Link to item Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2009 Traditionally, it was believed that cardiac rhythm stability was governed by the slope of the restitution curve (RC), which relates the duration of an action potential to the preceding diastolic interval. However, a single RC does not exist; rate-dependenc ... Full text Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · 2009 Cite

Variability of action potential duration in pharmacologically induced long QT syndrome type 1.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · January 1, 2009 Long QT Syndrome (LQTS) is a congenital disorder associated with life-threatening arrhythmias. LQT1, a type of LQTS affecting the slow delayed rectifier potassium current, shows a higher incidence of arrhythmia associated with sympathetic stimulation than ... Cite

`Cardiac alternans arising from an unfolded border-collision bifurcation

Journal Article J. Comput. Nonlinear Dynam. · October 2008 Link to item Cite

Cardiac alternans arising from an unfolded border-collision bifurcation

Journal Article 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007 · January 1, 2008 Following an electrical stimulus, the transmembrane voltage of cardiac tissue rises rapidly and remains at a constant value before returning to the resting value, a phenomenon known as an action potential. When the pacing rate of a periodic train of stimul ... Full text Cite

Period-doubling bifurcation to alternans in paced cardiac tissue: crossover from smooth to border-collision characteristics

Journal Article Physical review letters · August 3, 2007 We investigate, both experimentally and theoretically, the period-doubling bifurcation to alternans in heart tissue. Previously, this phenomenon has been modeled with either smooth or border-collision dynamics. Using a modification of existing experimental ... Cite

Period-doubling bifurcation to alternans in paced cardiac tissue: crossover from smooth to border-collision characteristics.

Journal Article Physical review letters · August 2007 We investigate, both experimentally and theoretically, the period-doubling bifurcation to alternans in heart tissue. Previously, this phenomenon has been modeled with either smooth or border-collision dynamics. Using a modification of existing experimental ... Full text Cite

Spatial heterogeneity of the restitution portrait in rabbit epicardium.

Journal Article Am J Physiol Heart Circ Physiol · March 2007 Spatial heterogeneity of repolarization can provide a substrate for reentry to occur in myocardium. This heterogeneity may result from spatial differences in action potential duration (APD) restitution. The restitution portrait (RP) measures many aspects o ... Full text Link to item Cite

An ionically based mapping model with memory for cardiac restitution.

Journal Article Bulletin of mathematical biology · February 2007 Many features of the sequence of action potentials produced by repeated stimulation of a patch of cardiac muscle can be modeled by a 1D mapping, but not the full behavior included in the restitution portrait. Specifically, recent experiments have found tha ... Full text Cite

Modeling electroporation in a single cell.

Journal Article Biophysical journal · January 2007 Electroporation uses electric pulses to promote delivery of DNA and drugs into cells. This study presents a model of electroporation in a spherical cell exposed to an electric field. The model determines transmembrane potential, number of pores, and distri ... Full text Cite

The Electrocardiogram Restitution Portrait Quantifying Dynamical Electrical Instability in Young Myocardium.

Journal Article Comput Cardiol · 2007 Novel methods need to be developed to detect electrical instability in children. The dynamical properties of action potential restitution play an important role in the development of instability leading to arrhythmias. A new method, the Restitution Portrai ... Link to item Cite

A model-independent technique for eigenvalue identification and its application in predicting cardiac alternans

Journal Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 2007 Predicting cardiac alternans is a crucial step toward detection and prevention of ventricular fibrillation, a heart rhythm disorder that kills hundreds of thousands of people in the US each year. According to the theory of dynamical systems, cardiac altern ... Full text Cite

Guidelines for controlling pore radii from nonlinear analysis of a two-dimensional model of electroporation

Journal Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 2007 Electroporation, in which strong electric pulses create transient pores in the cell membrane, is commonly used as a method for delivering molecules into cells. One of the pulsing protocols used in practice, a two-pulse protocol, creates a certain number of ... Full text Cite

Singular perturbation analysis of the pore creation transient.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · September 2006 Electroporation, in which electric pulses create transient pores in the cell membrane, is an important technique for drug and DNA delivery. Electroporation kinetics is mathematically described by an advection-diffusion boundary value problem. This study us ... Full text Cite

Feasibility of non-invasive determination of the stability of propagation reserve in patients

Journal Article Computing in Cardiology · December 1, 2012 This study investigates the feasibility of using surface ECG recordings to assess stability of cardiac propagation. Our novel method customizes a reaction-diffusion model of cardiac excitation using measurements of patient's repolarization dynamics. The cu ... Cite

Asymptotic model of electrical stimulation of nerve fibers.

Journal Article Medical & biological engineering & computing · March 2012 We present a novel theory and computational algorithm for modeling electrical stimulation of nerve fibers in three dimensions. Our approach uses singular perturbation to separate the full 3D boundary value problem into a set of 2D "transverse" problems cou ... Full text Cite

Theory of electroporation

Journal Article · December 1, 2009 Experiments conducted on artificial bilayers, suspensions of vesicles or cells, and tissues have demonstrated that a large, externally induced transmembrane potential (V m) causes an increase in the conductivity of the membrane by five to six orders of mag ... Full text Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · December 1, 2009 Traditionally, it was believed that cardiac rhythm stability was governed by the slope of the restitution curve (RC), which relates the duration of an action potential to the preceding diastolic interval. However, a single RC does not exist; rate-dependenc ... Cite

Activating function of needle electrodes in anisotropic tissue

Journal Article Med. Biol. Eng. Comput. · 2009 Cite

Variability of action potential duration in pharmacologically induced long QT syndrome type 1.

Journal Article Annu Int Conf IEEE Eng Med Biol Soc · 2009 Long QT Syndrome (LQTS) is a congenital disorder associated with life-threatening arrhythmias. LQT1, a type of LQTS affecting the slow delayed rectifier potassium current, shows a higher incidence of arrhythmia associated with sympathetic stimulation than ... Full text Link to item Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2009 Traditionally, it was believed that cardiac rhythm stability was governed by the slope of the restitution curve (RC), which relates the duration of an action potential to the preceding diastolic interval. However, a single RC does not exist; rate-dependenc ... Full text Cite

Spatial heterogeneity of restitution properties and the onset of alternans.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · 2009 Cite

Variability of action potential duration in pharmacologically induced long QT syndrome type 1.

Journal Article Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference · January 1, 2009 Long QT Syndrome (LQTS) is a congenital disorder associated with life-threatening arrhythmias. LQT1, a type of LQTS affecting the slow delayed rectifier potassium current, shows a higher incidence of arrhythmia associated with sympathetic stimulation than ... Cite

`Cardiac alternans arising from an unfolded border-collision bifurcation

Journal Article J. Comput. Nonlinear Dynam. · October 2008 Link to item Cite

Cardiac alternans arising from an unfolded border-collision bifurcation

Journal Article 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2007 · January 1, 2008 Following an electrical stimulus, the transmembrane voltage of cardiac tissue rises rapidly and remains at a constant value before returning to the resting value, a phenomenon known as an action potential. When the pacing rate of a periodic train of stimul ... Full text Cite

Period-doubling bifurcation to alternans in paced cardiac tissue: crossover from smooth to border-collision characteristics

Journal Article Physical review letters · August 3, 2007 We investigate, both experimentally and theoretically, the period-doubling bifurcation to alternans in heart tissue. Previously, this phenomenon has been modeled with either smooth or border-collision dynamics. Using a modification of existing experimental ... Cite

Period-doubling bifurcation to alternans in paced cardiac tissue: crossover from smooth to border-collision characteristics.

Journal Article Physical review letters · August 2007 We investigate, both experimentally and theoretically, the period-doubling bifurcation to alternans in heart tissue. Previously, this phenomenon has been modeled with either smooth or border-collision dynamics. Using a modification of existing experimental ... Full text Cite

Spatial heterogeneity of the restitution portrait in rabbit epicardium.

Journal Article Am J Physiol Heart Circ Physiol · March 2007 Spatial heterogeneity of repolarization can provide a substrate for reentry to occur in myocardium. This heterogeneity may result from spatial differences in action potential duration (APD) restitution. The restitution portrait (RP) measures many aspects o ... Full text Link to item Cite

An ionically based mapping model with memory for cardiac restitution.

Journal Article Bulletin of mathematical biology · February 2007 Many features of the sequence of action potentials produced by repeated stimulation of a patch of cardiac muscle can be modeled by a 1D mapping, but not the full behavior included in the restitution portrait. Specifically, recent experiments have found tha ... Full text Cite

Modeling electroporation in a single cell.

Journal Article Biophysical journal · January 2007 Electroporation uses electric pulses to promote delivery of DNA and drugs into cells. This study presents a model of electroporation in a spherical cell exposed to an electric field. The model determines transmembrane potential, number of pores, and distri ... Full text Cite

The Electrocardiogram Restitution Portrait Quantifying Dynamical Electrical Instability in Young Myocardium.

Journal Article Comput Cardiol · 2007 Novel methods need to be developed to detect electrical instability in children. The dynamical properties of action potential restitution play an important role in the development of instability leading to arrhythmias. A new method, the Restitution Portrai ... Link to item Cite

A model-independent technique for eigenvalue identification and its application in predicting cardiac alternans

Journal Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 2007 Predicting cardiac alternans is a crucial step toward detection and prevention of ventricular fibrillation, a heart rhythm disorder that kills hundreds of thousands of people in the US each year. According to the theory of dynamical systems, cardiac altern ... Full text Cite

Guidelines for controlling pore radii from nonlinear analysis of a two-dimensional model of electroporation

Journal Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) · January 1, 2007 Electroporation, in which strong electric pulses create transient pores in the cell membrane, is commonly used as a method for delivering molecules into cells. One of the pulsing protocols used in practice, a two-pulse protocol, creates a certain number of ... Full text Cite

Singular perturbation analysis of the pore creation transient.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · September 2006 Electroporation, in which electric pulses create transient pores in the cell membrane, is an important technique for drug and DNA delivery. Electroporation kinetics is mathematically described by an advection-diffusion boundary value problem. This study us ... Full text Cite

Reproducing cardiac restitution properties using the Fenton-Karma membrane model.

Journal Article Annals of biomedical engineering · July 2005 Modern models of cardiac membranes are often highly complex and computationally expensive, particularly when used in long simulations of spatially extended models of cardiac tissue. Therefore, there is a need for simpler membrane models that preserve the f ... Full text Cite

Restitution in mapping models with an arbitrary amount of memory.

Journal Article Chaos (Woodbury, N.Y.) · June 2005 Restitution, the characteristic shortening of action potential duration (APD) with increased heart rate, has been studied extensively because of its purported link to the onset of fibrillation. Restitution is often represented in the form of mapping models ... Full text Cite

Bistability and correlation with arrhythmogenesis in a model of the right atrium.

Journal Article Annals of biomedical engineering · May 2005 Rapid pacing is an important tool for understanding cardiac arrhythmias. A recent experiment involving rapid pacing of sheep atria indicated that the initiation of atrial arrhythmias may be related to the 1:1/2:1 bistability. To elucidate the mechanism of ... Full text Cite

The restitution portrait: a new method for investigating rate-dependent restitution.

Journal Article J Cardiovasc Electrophysiol · June 2004 INTRODUCTION: Electrical restitution, relating action potential duration (APD) to diastolic interval (DI), was believed to determine the stability of heart rhythm. However, recent studies demonstrate that stability also depends on long-term APD changes cau ... Full text Link to item Cite

Model of creation and evolution of stable electropores for DNA delivery.

Journal Article Biophysical journal · May 2004 Electroporation, in which electric pulses create transient pores in the cell membrane, is becoming an important technique for gene therapy. To enable entry of supercoiled DNA into cells, the pores should have sufficiently large radii (>10 nm), remain open ... Full text Cite

Electric field of a six-needle array electrode used in drug and DNA delivery in vivo: analytical versus numerical solution.

Journal Article IEEE transactions on bio-medical engineering · November 2003 We present an analytical solution for the electrical potential and field established by a six-needle array electroporation electrode, which is used in vivo for cancer treatment and DNA delivery. The analytical solution closely matches the numerical solutio ... Full text Cite

Electrical energy required to form large conducting pores.

Journal Article Bioelectrochemistry (Amsterdam, Netherlands) · August 2003 This study computes the contribution of the externally induced transmembrane potential to the energy of large, highly conductive pores. This work was undertaken because the pore energy formulas existing in the literature predict qualitatively different beh ... Full text Cite

Condition for alternans and stability of the 1:1 response pattern in a "memory" model of paced cardiac dynamics.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · March 2003 We analyze a mathematical model of paced cardiac muscle consisting of a map relating the duration of an action potential to the preceding diastolic interval as well as the preceding action potential duration, thereby containing some degree of "memory." The ... Full text Cite

Modeling postshock evolution of large electropores

Journal Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics · February 1, 2003 The modeling of postshock evolution of large electrophores was discussed. Pores in a homogeneous population either shrink to zero or assume a stable radius corresponding to the minimum of the bilayer energy. For a hetergeneous population, such a stable rad ... Cite

Viability of cancer cells exposed to pulsed electric fields: the role of pulse charge.

Journal Article Annals of biomedical engineering · January 2003 The goal of this study was to collect a comprehensive set of data that related lethal effects of electric fields to the duration of the pulse. Electric pulses of different strengths and durations were applied to a suspension of HEp-2 cells (epidermoid carc ... Full text Cite

Field stimulation of cardiac fibers with random spatial structure.

Journal Article IEEE transactions on bio-medical engineering · January 2003 Polarization of individual cells ("sawtooth") has been proposed as a mechanism for field stimulation and defibrillation. To date, the modeling work has concentrated on the myocardium with periodic spatial structure; this paper investigates potentials arisi ... Full text Cite

Modeling postshock evolution of large electropores

Journal Article Phys. Rev. E, Stat. Nonlinear Soft Matter Phys. (USA) · 2003 The Smoluchowski equation (SE), which describes the evolution of pores created by electric shocks, cannot be applied to modeling large and long-lived pores for two reasons: (1) it does not predict pores of radius above 20 nm without also predicting membran ... Full text Link to item Cite

Modelling induction of a rotor in cardiac muscle by perpendicular electric shocks.

Journal Article Medical & biological engineering & computing · January 2002 A strong, properly timed shock applied perpendicularly to a propagating wavefront causes a rotor in the canine myocardium. Experimental data indicate that the induction of this rotor relies on the shock exciting tissue away from the electrodes. The computa ... Full text Cite

Existence of bistability and correlation with arrhythmogenesis in paced sheep atria.

Journal Article Journal of cardiovascular electrophysiology · July 2000 IntroductionStudies of the electrical dynamics of cardiac tissue are important for understanding the mechanisms of arrhythmias. This study uses high-frequency pacing to investigate the dynamics of sheep atria.Methods and resultsA 504-elec ... Full text Cite

Increasing the computational efficiency of a bidomain model of defibrillation using a time-dependent activating function.

Journal Article Annals of biomedical engineering · July 2000 Realistic simulations of the effects of strong shocks on cardiac muscle require solving the bidomain model, a continuum representation of cardiac tissue by a system of two reaction-diffusion equations. For two- and three-dimensional problems, the computati ... Full text Cite

Theoretical modeling of the effects of shock duration, frequency, and strength on the degree of electroporation.

Journal Article Bioelectrochemistry (Amsterdam, Netherlands) · June 2000 Electroporation is becoming an increasingly important tool for introducing biologically active compounds into living cells, yet the effectiveness of this technique can be low, particularly in vivo. One way to improve the success rate is to optimize the sho ... Full text Cite

Transitions between 2:1 and 1:1 responses in cardiac muscle induced by added stimuli

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 We demonstrate experimentally that transitions can be induced between stable coexisting response patterns in bullfrog ventricular myocardium by means of a single pulse injected into the stimulus train. We find that two distinct ranges of stimulus timings w ... Cite

Existence of bistability and correlation with arrhythmogenesis in sheep atria

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 This experimental study investigates the response of sheep atria to periodic pacing. In 23 trials over 6 animals, a window of bistability was observed wherein for a range of pacing periods the atria responded 1:1 or 2:1 depending on whether pacing period w ... Cite

Electroporation of single cells by high frequency shocks

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 This modeling study investigates electroporation in a single cell exposed to a 10 ms pulse train consisting of high frequency monophasic or biphasic shocks. The fraction of the cell membrane occupied by pores decreases with frequency, and the decrease is m ... Cite

Reduced bidomain model of defibrillation

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 Bidomain model of the myocardium has been successfully used in predicting the tissue response to a strong shock. The studies of active tissue behavior have been limited due the computational expense of solving bidomain equations. The goal of the present re ... Cite

Modeling induction of reentry with a realistic S2 stimulus

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 Reentry in cardiac tissue has been attained experimentally in a canine model using cross-field extracellular stimulation. However, the mechanisms by which large areas of activation away from the shock electrode occur and initiate reentry remain unclear. Th ... Cite

Modeling electroporation in a single cell. I. Effects Of field strength and rest potential.

Journal Article Biophysical journal · September 1999 This study develops a model for a single cell electroporated by an external electric field and uses it to investigate the effects of shock strength and rest potential on the transmembrane potential V(m) and pore density N around the cell. As compared to th ... Full text Cite

Effects of electroporation on the transmembrane potential distribution in a two-dimensional bidomain model of cardiac tissue.

Journal Article Journal of cardiovascular electrophysiology · May 1999 IntroductionDefibrillation shocks, when delivered through internal electrodes, establish transmembrane potentials (Vm) large enough to electroporate the membrane of cardiac cells. The effects of such shocks on the transmembrane potential distribut ... Full text Cite

Modeling electroporation in a single cell. II. Effects of ionic concentrations

Journal Article Biophys. J. (USA) · 1999 For pt. I see ibid., vol. 77, p. 1213-24 (1999). This study expands a previously developed model (described in pt. I) of a single cell electroporated by an external electric field by explicitly accounting for the ionic composition of the electroporation cu ... Cite

Field stimulation of isolated chick heart cells: comparison of experimental and theoretical activation thresholds.

Journal Article Journal of cardiovascular electrophysiology · January 1999 IntroductionThis study examines the accuracy of using membrane models to predict activation thresholds for chick heart cells during field stimulation.Methods and resultsActivation thresholds were measured experimentally in ten embryonic c ... Full text Cite

Asymptotic model of electroporation

Journal Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics · January 1, 1999 Electroporation is described mathematically by a partial differential equation (PDE) that governs the distribution of pores as a function of their radius and time. This PDE does not have an analytical solution and, because of the presence of disparate spat ... Full text Cite

Electroporation and shock-induced transmembrane potential in a cardiac fiber during defibrillation strength shocks.

Journal Article Annals of biomedical engineering · July 1998 Experimental studies have shown that the magnitude of the shock-induced transmembrane potential (Vm) saturates with increasing electric field strength. This study uses a mathematical model to investigate the effects of electroporation and membrane kinetics ... Full text Cite

The induction of reentry in cardiac tissue. The missing link: How electric fields alter transmembrane potential

Journal Article Chaos · January 1, 1998 This review examines the initiation of reentry in cardiac muscle by strong electric shocks. Specifically, it concentrates on the mechanisms by which electric shocks change the transmembrane potential of the cardiac membrane and create the physiological sub ... Full text Cite

Role of spatial interactions in creating the dispersion of transmembrane potential by premature electric shocks

Journal Article Annals of Biomedical Engineering · 1997 Strong electric shocks applied during the refractory period can initiate or terminate cardiac arrhythmias. To elucidate the underlying mechanism, Knisley et al. used rabbit papillary muscle in vitro to scan the refractory period of an action potential with ... Cite

Initiation of propagation in a one-dimensional excitable medium

Journal Article Physica D: Nonlinear Phenomena · January 1, 1997 This study examines the initiation of propagation in a one-dimensional fiber by local stimulation with a small electrode. The membrane dynamics is based on the generic FitzHugh-Nagumo model, reduced in a singular limit to a nonlinear heat equation. A stead ... Full text Cite

Electroporation as a mechanism of the saturation of transmembrane potential induced by large electric fields

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1996 Experimental studies have shown that the magnitude of a shock-induced transmembrane potential increases only slightly with any increase in the strength of the electric field above approximately 7 V/cm. In this study, computer simulations of both passive an ... Cite

Virtual electrode effects in a bidomain model with electroporating membrane

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1995 This study examines the effects of electroporation in a computer simulation of the response of a two-dimensional slice of myocardium to electrical stimulation. The multicellular, syncytial cardiac tissue is represented by the bidomain model. Electroporatio ... Cite

Macroscopic model of electroporating membrane

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1995 This study presents a concise macroscopic model of electroporating membrane. The membrane is represented by a parallel-conductance model in which the transmembrane current consists of the capacitive current, the leakage current, and the electroporation cur ... Cite

Effects of electroporation on transmembrane potential induced by defibrillation shocks.

Journal Article Pacing and clinical electrophysiology : PACE · September 1995 This study uses a one-dimensional model of cardiac strand to investigate the effects of electroporation on transmembrane potential (Vm) induced by defibrillation shocks. The strand is stimulated at the ends by extracellular electrodes. Its membrane, when e ... Full text Cite

Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation.

Journal Article Journal of cardiovascular electrophysiology · September 1995 IntroductionThe truncated exponential waveform from an implantable cardioverter defibrillator can be described by three quantities: the leading edge voltage, the waveform duration, and the waveform time constant (tau s). The goal of this work was ... Full text Cite

Effects of electroporation on transmembrane potential induced by defibrillation shocks

Journal Article PACE - Pacing and Clinical Electrophysiology · 1995 This study uses a one-dimensional model of cardiac strand to investigate the effects of electroporation on transmembrane potential (V(m)) induced by defibrillation shocks. The strand is stimulated at the ends by extracellular electrodes. Its membrane, when ... Cite

Response of a single cell to an external electric field.

Journal Article Biophysical journal · June 1994 The response of a cell to an external electric field is investigated using dimensional analysis and singular perturbation. The results demonstrate that the response of a cell is a two-stage process consisting of the initial polarization that proceeds with ... Full text Cite

Strength-interval curves in canine myocardium at very short cycle lengths.

Journal Article Pacing Clin Electrophysiol · May 1994 While ventricular electrophysiological properties have been intensively studied at normal heart rates, little is known about these properties at the very short cycle lengths (approximately 100 msec), which are present in ventricular fibrillation. We examin ... Full text Link to item Cite

Effective boundary conditions for syncytial tissues.

Journal Article IEEE transactions on bio-medical engineering · February 1994 This study derives effective boundary conditions for potentials and currents on the interface between syncytial tissue and a surrounding volume conductor. The derivation is based on an idealized representation of the syncytium as a network of interconnecte ... Full text Cite

Boundary conditions for the bidomain model of the heart

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1993 This study resolves the long-debated question of the appropriate boundary conditions for the bidomain model. the derivation assumes that the myocardium consists of interconnected cells arranged periodically in space and, on the boundary, the extracellular ... Cite

Effective defibrillation in pigs using interleaved and common phase sequential biphasic shocks.

Journal Article Pacing and clinical electrophysiology : PACE · August 1993 Previous studies have shown that low internal defibrillation thresholds (DFTs) can be attained by using two pairs of electrodes and combining biphasic shocks with sequential timing. The purpose of this two-part study was to test the defibrillation efficacy ... Full text Cite

Homogenization of syncytial tissues.

Journal Article Critical reviews in biomedical engineering · January 1993 This article derives a continuum representation of a multicellular, syncytial tissue directly from its microstructure and basic physical principles. The final equations for the homogenized syncytium contain the bidomain model as a special case. The derivat ... Cite

Propagation versus delayed activation during field stimulation of cardiac muscle.

Journal Article Pacing and clinical electrophysiology : PACE · February 1992 This modeling study seeks to explain the experimentally detected delay between the application of an electric field and the recorded response of the transmembrane potential. In this experiment, conditions were deliberately set so that the field should exci ... Full text Cite

Two-scale asymptotic analysis for modeling activation of periodic cardiac strand

Journal Article Mathematical and Computer Modelling · January 1, 1992 This work explores the applicability of two-scale asymptotic analysis to model the excitable cardiac strand with periodic discontinuities. The strand is composed of 60 cells connected by junctions. The membrane excitability is modeled using Ebihara-Johnson ... Full text Cite

Pacing thresholds for cathodal and anodal high-frequency monophasic pulses

Journal Article Journal of Cardiovascular Electrophysiology · January 1, 1992 Introduction: The purpose of this study was to investigate ventricular pacing with bursts of high-frequency monophasic pulses using mathematical modeling and animal experiments. The study concentrated on the dependence of anodal and cathodal thresholds on ... Full text Cite

Do myocardial fibers contain junctional capacitance?

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1991 A computer model was used to evaluate whether capacitance at the junctions between myocardial cells could be discerned from the time course of the axial potential during a step current. Three modeled pathways were examined; 1) continuous core conductor, 2) ... Cite

Electrostatic potential on the boundary of cardiac tissue

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1991 The goal of this study is to determine the distribution of an electrostatic potential on the boundary of cardiac tissue. The mathematical development, based on the two-scale asymptotic expansion and boundary layer theory, is presented for the case of Neuma ... Cite

Current concepts for selecting the location, size and shape of defibrillation electrodes.

Journal Article Pacing and clinical electrophysiology : PACE · February 1991 Full text Cite

Modeling high-frequency pacing with a discrete cardiac strand

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1990 A computer model of a one-dimensional cardiac strand composed of separate cells connected by junctions was used to determine stimulation thresholds for pacing with 2-ms bursts of high-frequency monophase pulses. Two models of cardiac strand were used: a st ... Cite

Modeling in the Bioelectric Stimulation Unit

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1990 The research program of Unit 1.1C, Modeling in Bioelectric Stimulation, of the National Science Foundation/Engineering Research Center (NSF/ERC) is described. The modeling effort is centered around problems associated with cardiac electric fields, those ar ... Cite

Effect of intercellular capacitance on conduction in a model of cell uncoupling

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1990 Velocity of action potential propagation along a cardiac cell strand is studied as a function of intercellular junctional capacitance and resistance (cj and rj). For a given rj, a larger cj increases velocity. Thus, velocity slowing due to increased rj is ... Cite

Potential distribution in three-dimensional periodic myocardium--Part II: Application to extracellular stimulation.

Journal Article IEEE transactions on bio-medical engineering · March 1990 Modeling potential distribution in the myocardium treated as a periodic structure implies that activation from high-current stimulation with extracellular electrodes is caused by the spatially oscillating components of the transmembrane potential. This hyp ... Full text Cite

Potential distribution in three-dimensional periodic myocardium--Part I: Solution with two-scale asymptotic analysis.

Journal Article IEEE transactions on bio-medical engineering · March 1990 The use of two-scale asymptotic analysis allows development of a model of the steady-state potential distribution in three-dimensional cardiac muscle preserving the underlying cellular network. The myocardium is modeled as a periodic structure consisting o ... Full text Cite

Experimental evidence for autowaves in the heart.

Journal Article Annals of the New York Academy of Sciences · January 1990 Full text Cite

Experimental results pertinent to the modelling of defibrillation

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · November 1, 1989 Recent experimental results pertinent to the modeling of defibrillation are presented. The extracellular potential gradient created by a large electric stimulus predicts whether or not several different types of electrophysiologic response will occur for a ... Cite

Modelling the periodicity of cardiac muscle.

Journal Article Journal of electrocardiology · January 1989 The intractable problem of modelling cardiac muscle of arbitrary extent while preserving cellular structure has been solved using an analytical rather than numerical approach with a method called two-scale asymptotic analysis. In this method, the myocardiu ... Full text Cite

Extracellular field required for excitation in three-dimensional anisotropic canine myocardium.

Journal Article Circulation research · July 1988 It is not known how well potential gradient, current density, and energy correlate with excitation by extracellular stimulation in the in situ heart. Additionally, the influence of fiber orientation and stimulus polarity on the extracellular thresholds for ... Full text Cite

Transmural activations and stimulus potentials in three-dimensional anisotropic canine myocardium.

Journal Article Circulation research · July 1988 Epicardial and endocardial pacing are widely used, yet little is known about the three-dimensional distribution of potentials generated by the pacing stimulus or the spread of activation from these pacing sites. In six open-chest dogs, simultaneous recordi ... Full text Cite

Finite element approximation of potential gradient in cardiac muscle undergoing stimulation

Journal Article Mathematical and Computer Modelling · January 1, 1988 Depolarization and defibrillation events in cardiac muscle are considered to be closely related to the potential gradient existing in the myocardium during electrical shock. Therefore, a numerical technique of calculating the gradient from experimental dat ... Full text Cite

Anodal and cathodal thresholds during transthoracic stimulation

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · January 1, 1988 A physiological mechanism is proposed for a phenomenon observed in experimental studies: the ventricular threshold during transthoracic stimulation is slightly lower if the electrode closer to the heart is a cathode rather than an anode. This result can be ... Full text Cite

FEASIBILITY OF ESTIMATING ENDOCARDIAL POTENTIALS FROM CAVITY POTENTIALS.

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · December 1, 1987 The feasibility of estimating endocardial potentials from cavity potentials is assessed quantitatively. The model considered is an electrically homogeneous cavity region bounded externally by the endocardial surface and by the surface of the intracavity pr ... Cite

Periodic conductivity as a mechanism for cardiac stimulation and defibrillation.

Journal Article IEEE transactions on bio-medical engineering · July 1987 Full text Cite

The closed form solution to the periodic core-conductor model using asymptotic analysis.

Journal Article IEEE transactions on bio-medical engineering · July 1987 Full text Cite

ASYMPTOTIC ANALYSIS FOR PERIODIC CARDIAC MUSCLE.

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · December 1, 1986 The problem of determining the potential distribution in a strand of cardiac cells is solved using asymptotic analysis. The intracellular, extracellular, and transmembrane potentials are treated as dependent upon the variable X in two ways: first, aperiodi ... Cite

Computerized system for isochronic epicardial mapping

Journal Article Medical Informatics · 1985 A minicomputer system for isochronic map generation was devised to measure the spread of activation over the cardiac muscle. The system consists of minicomputer (MERA 400) and a CAMAC, which control the acquisition of ECG signals and graphic output of maps ... Cite