Definition, estimation and limitations of the dominant frequency in intracardiac electrograms

AbstractIntracardiac electrogram recordings during atrial fibrillation (AFib) are characterized by irregular rhythms and complex morphologies. Hence, analysis in the time domain is a difficult task. The so called dominant frequency DF is a spectrum based approach that aims at finding the most relevant frequency in a signal providing information about the rate and dynamics of AFib. However, in recent years various studies reported controversial results regarding the clinical relevance of the DF. In this work, a definition of the DF at a fundamental scale is proposed as the rate at which action potentials are triggered in atrial cells. The most common method to estimate the DF in literature, labeled as DFSpec, is examined in comparison to the proposed definition. A signal processing study using synthetic signals verified that the DFSpec is stable for all changes in morphology of atrial activations. However, it is also demonstrated that the DFSpec becomes unstable for variations above 20% in the cycle length of a signal. Spectrum based DF estimation should be interpreted in a critical manner and is not advisable for study endpoints or clinical markers.

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Electrical interactions between a rabbit atrial cell and a nodal cell model

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1998.274.6.h2152 ◽

1998 ◽

Vol 274 (6) ◽

pp. H2152-H2162 ◽

Cited By ~ 12

Author(s):

Ronald W. Joyner ◽

Rajiv Kumar ◽

David A. Golod ◽

Ronald Wilders ◽

Habo J. Jongsma ◽

...

Keyword(s):

Action Potentials ◽

Cycle Length ◽

Cell Model ◽

Stimulus Frequency ◽

Input Resistance ◽

Sa Node ◽

Atrial Cells ◽

Model Cell ◽

Atrial Cell ◽

Basic Cycle Length

Atrial activation involves interactions between cells with automaticity and slow-response action potentials with cells that are intrinsically quiescent with fast-response action potentials. Understanding normal and abnormal atrial activity requires an understanding of this process. We studied interactions of a cell with spontaneous activity, represented by a “real-time” simulation of a model of the rabbit sinoatrial (SA) node cell, simultaneously being electrically coupled via our “coupling clamp” circuit to a real, isolated atrial myocyte with variations in coupling conductance ( G c) or stimulus frequency. The atrial cells were able to be driven at a regular rate by a single SA node model (SAN model) cell. Critical G c for entrainment of the SAN model cell to a nonstimulated atrial cell was 0.55 ± 0.05 nS ( n = 7), and the critical G c that allowed entrainment when the atrial cell was directly paced at a basic cycle length of 300 ms was 0.32 ± 0.01 nS ( n = 7). For each atrial cell we found periodic phenomena of synchronization other than 1:1 entrainment when G c was between 0.1 and 0.3 nS, below the value required for frequency entrainment, when the atrial cell was directly driven at a basic cycle length of either 300 or 600 ms. In conclusion, the high input resistance of the atrial cells allows successful entrainment of nodal and atrial cells at low values of G c, but further uncoupling produces arrhythmic interactions.

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Letter by Platonov et al Regarding Article, “Dominant Frequency of Atrial Fibrillation Correlates Poorly With Atrial Fibrillation Cycle Length”

Circulation Arrhythmia and Electrophysiology ◽

10.1161/circep.110.943274 ◽

2010 ◽

Vol 3 (2) ◽

Cited By ~ 3

Author(s):

Pyotr G. Platonov ◽

Martin Stridh ◽

Leif Sörnmo

Keyword(s):

Atrial Fibrillation ◽

Cycle Length ◽

Dominant Frequency

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Generalized Wavelet Fisher’s Information of1/fαSignals

Advances in Mathematical Physics ◽

10.1155/2015/210592 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Julio Ramírez-Pacheco ◽

Homero Toral-Cruz ◽

Luis Rizo-Domínguez ◽

Joaquin Cortez-Gonzalez

Keyword(s):

Fisher Information ◽

Gaussian Noise ◽

Structural Breaks ◽

Wavelet Domain ◽

Fractional Gaussian Noise ◽

Domain Definition ◽

Potential Applications ◽

Definition Of ◽

The Time Domain ◽

Fisher's Information

This paper defines the generalized wavelet Fisher information of parameterq. This information measure is obtained by generalizing the time-domain definition of Fisher’s information of Furuichi to the wavelet domain and allows to quantify smoothness and correlation, among other signals characteristics. Closed-form expressions of generalized wavelet Fisher information for1/fαsignals are determined and a detailed discussion of their properties, characteristics and their relationship with waveletq-Fisher information are given. Information planes of1/fsignals Fisher information are obtained and, based on these, potential applications are highlighted. Finally, generalized wavelet Fisher information is applied to the problem of detecting and locating weak structural breaks in stationary1/fsignals, particularly for fractional Gaussian noise series. It is shown that by using a joint Fisher/F-Statistic procedure, significant improvements in time and accuracy are achieved in comparison with the sole application of theF-statistic.

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Abstract 4104: Organization of Atrial Signals is Critical Prior to Cardioversion of Atrial Fibrillation with Intravenous Flecainide: Insight from Spectral Analysis of Intracardiac Electrograms

Circulation ◽

10.1161/circ.118.suppl_18.s_829-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Jiun Tuan ◽

Suman Kundu ◽

Mohamed Jeilan ◽

Faizel Osman ◽

Rajkumar Mantravadi ◽

...

Keyword(s):

Atrial Fibrillation ◽

Spectral Analysis ◽

Catheter Ablation ◽

Cycle Length ◽

Dominant Frequency ◽

Relative Increase ◽

Significant Difference ◽

Before And After ◽

Atrial Activation ◽

Relative Change

Introduction & Hypothesis: Studies in catheter ablation of atrial fibrillation (AF) show that an increase in cycle length (CL) and higher organization index (OI) is associated with termination of AF. We hypothesize that similar changes can be seen in chemical cardioversion with Flecainide Methods: Patients who were still in AF at the end of catheter ablation for AF were given intravenous flecainide. OI and dominant frequency (DF) were obtained by Fast Fourier Transform of coronary sinus electrograms over 10s in AF, before and after flecainide infusion. Mean CL was also calculated. Results: 28 patients were identified (18 paroxysmal AF and 10 persistent AF). 8 cardioverted to sinus rhythm (SR) with flecainide. In all patients, mean CL increased from 211 ± 44 ms to 321 ± 85 ms (p <0.001). Mean DF decreased from 5.2 ± 1.03 Hz to 3.6 ± 1.04 Hz (p <0.001). Mean OI was 0.33 ± 0.13 before and 0.32 ± 0.11 after flecainide (p = 0.90). Comparing patients who cardioverted to SR with those who did not, OI post-flecainide was 0.41 ± 0.12 vs 0.29 ± 0.10 (p=0.013) and relative change in OI was 29 ± 33% vs −3.9 ± 27% (p=0.016) respectively. No significant difference was noted in the change in CL and DF in the 2 groups. Logistic regression showed that a greater relative increase in OI (p=0.04), a higher OI post-flecainide (p=0.03) and SR at start of procedure (p=0.03) are independently associated with cardioversion to SR with flecainide. Conclusion: Increase in OI, independent of changes to the CL and DF, appears critical to AF termination with flecainide. The increase in OI may reflect an increase in size and reduction in the number of re-entrant circuits, which together with slowing of atrial activation, result in return to SR.

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Input Resistance, Time Constants, and Spike Initiation

Biophysics of Computation ◽

10.1093/oso/9780195104912.003.0023 ◽

1998 ◽

Author(s):

Christof Koch

Keyword(s):

Membrane Potential ◽

Time Constant ◽

Action Potentials ◽

Input Resistance ◽

Current Injection ◽

Membrane Conductances ◽

Voltage Dependent ◽

Dc Component ◽

Definition Of ◽

A Current

This chapter represents somewhat of a tephnical interlude. Having introduced the reader to both simplified and more complex compartmental single neuron models, we need to revisit terrain with which we are already somewhat familiar. In the following pages we reevaluate two important concepts we defined in the first few chapters: the somatic input resistance and the neuronal time constant. For passive systems, both are simple enough variables: Rin is the change in somatic membrane potential in response to a small sustained current injection divided by the amplitude of the current injection, while τm is the slowest time constant associated with the exponential charging or discharging of the neuronal membrane in response to a current pulse or step. However, because neurons express nonstationary and nonlinear membrane conductances, the measurement and interpretation of these two variables in active structures is not as straightforward as before. Having obtained a more sophisticated understanding of these issues, we will turn toward the question of the existence of a current, voltage, or charge threshold at which a biophysical faithful model of a cell triggers action potentials. We conclude with recent work that suggests how concepts from the subthreshold domain, like the input resistance or the average membrane potential, could be extended to the case in which the cell is discharging a stream of action potentials. This chapter is mainly for the cognoscendi or for those of us that need to make sense of experimental data by comparing therp to theoretical models that usually fail to reflect reality adequately. In Sec. 3.4, we defined Kii (f) for passive cable structures as the voltage change at location i in response to a sinusoidal current injection of frequency f at the same location. Its dc component is also referred to as input resistance or Rin. Three difficulties render this definition of input resistance problematic in real cells: (1) most membranes, in particular at the soma, show voltage-dependent nonlinearities, (2) the associated ionic membrane conductances are time dependent and (3) instrumental aspects, such as the effect of the impedance of the recording electrode on Rin, add uncertainty to the measuring process.

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Application of Laplace Domain Waveform Inversion to Cross-Hole Radar Data

Remote Sensing ◽

10.3390/rs11161839 ◽

2019 ◽

Vol 11 (16) ◽

pp. 1839

Author(s):

Xu Meng ◽

Sixin Liu ◽

Yi Xu ◽

Lei Fu

Keyword(s):

Time Domain ◽

Waveform Inversion ◽

Radar Data ◽

Dominant Frequency ◽

Data Set ◽

Laplace Domain ◽

Full Waveform ◽

Highly Nonlinear ◽

The Time Domain ◽

Ground Penetrating

Full waveform inversion (FWI) can yield high resolution images and has been applied in Ground Penetrating Radar (GPR) for around 20 years. However, appropriate selection of the initial models is important in FWI because such an inversion is highly nonlinear. The conventional way to obtain the initial models for GPR FWI is ray-based tomogram inversion which suffers from several inherent shortcomings. In this paper, we develop a Laplace domain waveform inversion to obtain initial models for the time domain FWI. The gradient expression of the Laplace domain waveform inversion is deduced via the derivation of a logarithmic object function. Permittivity and conductivity are updated by using the conjugate gradient method. Using synthetic examples, we found that the value of the damping constant in the inversion cannot be too large or too small compared to the dominant frequency of the radar data. The synthetic examples demonstrate that the Laplace domain waveform inversion provide slightly better initial models for the time domain FWI than the ray-based inversion. Finally, we successfully applied the algorithm to one field data set, and the inverted results of the Laplace-based FWI show more details than that of the ray-based FWI.

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Rectification of muscarinic K+ current by magnesium ion in guinea pig atrial cells

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.253.1.h210 ◽

1987 ◽

Vol 253 (1) ◽

pp. H210-H214

Author(s):

M. Horie ◽

H. Irisawa

Keyword(s):

Guinea Pig ◽

Action Potentials ◽

Single Channel ◽

Outward Current ◽

Atrial Cells ◽

Voltage Dependent ◽

K Current ◽

Single Channel Currents ◽

Channel Currents ◽

Low K

Rectifying properties of the acetylcholine (ACh)-sensitive K+ channels were studied using a patch-clamp method in single atrial cells prepared enzymatically from adult guinea pig hearts. In the presence of micromolar concentration of nonhydrolyzable guanosine 5'-triphosphate (GTP) analogue 5'-guanylylimidodiphosphate (GppNHp) and the absence of Mg2+ at the inner surface of patch membrane [( Mg2+]i), the channel activity recovered in inside-out patch condition. The single channel conductance became ohmic between -80 and +80 mV (symmetrical 150 mM K+ solutions). The rapid relaxation of outward single channel currents was disclosed on a depolarization. [Mg2+]i blocked the outward current through the channel dose- and voltage-dependently and also induced a dose-dependent increase in the channel activation. The apparent paradoxical role of [Mg2+]i is important for the cholinergic control in the heart; voltage-dependent Mg block ensures a low K+ conductance of cell membrane at the plateau of action potentials during the exposure to ACh, thereby slowing the heart rate without unfavorable shortening of the action potentials.

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Effects of ischemic conditions and reperfusion on depolarization-induced automaticity

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1988.255.5.h992 ◽

1988 ◽

Vol 255 (5) ◽

pp. H992-H999 ◽

Cited By ~ 2

Author(s):

R. Mohabir ◽

G. R. Ferrier

Keyword(s):

Membrane Potential ◽

Action Potential ◽

Action Potentials ◽

Cycle Length ◽

Slow Inward Current ◽

Potential Range ◽

Ischemia And Reperfusion ◽

Slow Response ◽

Inward Current ◽

High Membrane Potential

The inducibility of slow-response automaticity was assessed during ischemic conditions and reperfusion by application of extracellular current. Isolated canine Purkinje fibers were depolarized to membrane potentials less than -65 mV to elicit depolarization-induced automaticity (DIA). Ischemic conditions increased the cycle length of DIA and, in some tissues, prevented sustained DIA or completely abolished DIA. The magnitude of depolarization required to elicit DIA also increased. Inhibition of DIA occurred at a time when action potential plateaus were abbreviated. The effect of reperfusion on DIA was biphasic. Initial reappearance of DIA was followed by inhibition and reduction of the membrane potential range over which DIA could be elicited. Plateaus of action potentials initiated at high membrane potential were abbreviated at this time. DIA returned again as reperfusion effects dissipated. Phasic changes in the inducibility of DIA may represent changes in availability of the slow inward current and may regulate the timing and types of arrhythmic activity occurring with ischemia and reperfusion.

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Investigating the Effect of Prestress Force on Cross-Tensioned Concrete Pavement Vibration

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120925670 ◽

2020 ◽

Vol 2674 (8) ◽

pp. 875-886

Author(s):

Hongduo Zhao ◽

Mengyuan Zeng ◽

Hui Chen ◽

Jianming Ling ◽

Difei Wu

Keyword(s):

Spectral Distribution ◽

Field Testing ◽

Dominant Frequency ◽

Fe Analysis ◽

Concrete Pavement ◽

Vibration Characteristics ◽

Dynamic Responses ◽

Power Spectral ◽

Force Monitoring ◽

The Time Domain

Prestress force loss is crucial to the structural performance of cross-tensioned concrete pavement (CTCP). Severe loss in prestress force will reduce the constricting-cracking capacity of the CTCP, resulting in damage with load and temperature applied. Vibration-based methods are commonly used in prestress force monitoring, but few relative studies are reported into CTCP and the relationship between prestress force and CTCP vibration is still unclear. The purpose of this paper is to investigate the effect of prestress force on CTCP vibration. The vibration characteristics of CTCP subjected to different prestress forces were studied through field testing and finite element (FE) analysis. Impulse load was applied as excitation at the anchorage zone and dynamic responses were measured in the time domain. A signal processing method was employed to obtain short-time power spectral from original vibration signals, which was utilized to extract vibration characteristics in time and frequency. As shown in both the field testing and the FE analysis, the prestress force has a more significant effect on frequency spectral distribution, rather than the dominant frequency. Integrated frequency is proved to be a reliable index for describing frequency spectral distribution and has a good correlation with prestress force, which suggests it can be used to reflect the change in prestress force. Overall, these findings indicate that vibration testing has potential in prestress force monitoring in CTCP, though the practicality of this method requires further demonstration.

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