Higher Dominant Frequency Research Articles

Influence of conspecifics and road noise on the properties ofthe advertisement call of Phyllodytes luteolus (Anura, Hylidae).

Acoustic communication in animals can be affected by multiple biotic (intra and interspecific) and abiotic (e.g., wind and rain) natural noises. In addition, human beings produce additional novel sources of noise, which can reduce or inhibit the reception of acoustic signals by conspecifics, leading to behavioral changes. In this study, we investigated whether sound of conspecifics and road noise additively affect the acoustic parameters of the advertisement call of males of a Yellow Heart-tongued Frog (Phyllodytes luteolus). We hypothesized that males that vocalize in choruses (males calling nearby) and in areas close to highways (anthropic noise) will increase their temporal and spectral acoustic parameters, respectively, to avoid acoustic signal masking. We recorded the vocalizations of 38 males in environments close (N = 18) to and distant (N = 20) from highways in different social contexts (many or few individuals calling nearby). Contrary to our expectation, the results indicated that males calling in areas close to highways had lower dominant frequency calls than those from natural areas (far from highways), and that the density of males in the chorus had no influence on the acoustic parameters. Furthermore, we found a positive relationship between body size and intensity, indicating that larger individuals can emit calls that can reach greater distances. The advertisement call of Phyllodytes luteolus has a high dominant frequency, with little overlap with the frequency of anthropic noises (roads), which may explain its presence and reproductive success of this species in bromeliads from urbanized areas.

Effect of cyclic loading level on mechanical response and microcracking behavior of saturated sandstones: Correlation with water weakening phenomenon

Rocks frequently endure water environments and diverse cyclic loading from natural and anthropogenic sources across various damage stages. Understanding the mechanical and fatigue behavior of saturated rocks under different cyclic loading levels is crucial for the intelligent design and long-term stability of the slope. Here, we report several monotonic and cyclic compression tests conducted on red and cyan sandstones under dry and water-saturated conditions, coupled with acoustic emission (AE) monitoring. We analyzed key mechanical parameters such as peak stress and peak strain, as well as AE parameters including count and energy, and dominant frequency in AE spectra. Our findings reveal that elevated cyclic loading levels significantly reduce peak stress and increase peak strain in both dry and water-saturated rocks, with more pronounced effects observed under water-saturated condition. The cumulative AE count correlates positively with increasing cyclic loading levels but decreases due to water saturation. Under cyclic loading with varying levels, dry rocks often experience shear cracking and exhibit AE waveform with high dominant frequency, while saturated rocks tend toward tensile cracking and AE waveform with low dominant frequency. Higher cyclic loading intensifies the occurrence of tensile cracking and AE waveform with low dominant frequency, which are constrained during the elastic deformation stage but become more pronounced beyond the crack initiation threshold. Moreover, cyclic loading enhances the water weakening effects in saturated rocks, closely associated with ongoing crack propagation within the rocks.

Influence of groundwater on micro-cracking behaviour and failure mechanism of deep hard rock

To address the water-inrush hazards encountered in deep tunnels in the rugged terrain of Southwest China, the uniaxial compression tests and acoustic emission (AE) monitoring were conducted on granite samples taken from a deep tunnel with different durations of saturation (2 days and 30 days), and the results were compared with those of natural granite samples. The results revealed the influence of groundwater on the mechanical properties, micro-cracking behavior, and failure modes of granite, which provided guidance for the deep tunnel construction. Based on the previous work, an optimized method for extracting the dominant frequency of rock AE signals considering the effect of groundwater on hard granite was proposed, which corrected the inaccurate extraction problem in the traditional method. The optimally extracted high dominant frequency AE signals could also be used as a precursor of rock failure.

House cricket males reared at different perceived acoustic population densities differ in adult behaviour but not physiology

Abstract If environments stay relatively constant over an individual's lifetime, a juvenile that accurately perceives environmental conditions, like population density, may adjust adult traits to better match their environment, thereby increasing success. While previous studies have explored how adult exposure to population density affects physiological and behavioural plasticity, the influence of juvenile density experience on adult traits is less studied. Using the common house cricket, Acheta domesticus, we explored whether perceived acoustic population density during development affected adult physiology and behaviour. We simulated high‐ and low‐densities using live ambient male song. Upon maturation, we measured metabolic (resting respiration) rate, reproductive investment (testes and accessory gland masses), calling song characteristics and aggressive behaviours from pairwise contests between males from different densities. Male rearing density did not affect resting metabolic rates or reproductive organ masses. However, high‐density males had significantly faster, longer chirps, with more pulses—known to be preferred by females—and higher dominant frequency. Low‐density males won more aggressive contests and sang the aggressive song more. Initiation of aggressive behaviours or song and singing more aggressive song were the only other significant predictors of contest outcome. These results suggest that males may plastically adjust calling song characteristics and aggressive behaviour, but not physiology, based on perceived density during development. We hypothesize that alternative mating tactics—that is, territory guarding versus attractive song production—may underlie these observed patterns. Overall, our study highlights the significant influence of early‐life biotic environments on adult behavioural decisions to enhance success in diverse environments.

Caterpillar sonic defences: diversity of vocalisations in silk and hawk moth (Bombycoidea) larvae

ABSTRACT Several Bombycoidea caterpillars, renowned for their large size and diverse appearances, possess an intriguing hidden talent – the ability to ‘vocalise’. Vocalisation is a rare form of sound production in insects, whereby sounds emanate from the oral cavity by air being forced through the foregut. Here, we report on vocalisation in 10 Bombycoidea species that occur across three families. Sounds in all 10 species are evoked in response to simulated predator attacks. Species were identified as vocalisers based primarily on video evidence of mouthparts being open during sound production. Vocalisations, when considered collectively across all 10 species studied, sound like a train of ‘hisses’ (sound units) that occur following an attack. Each sound unit comprises a series of pulses (4–104 on average) and is broadband with high dominant frequency (24–49 kHz on average). Given that vocalising species occur in different families across this large superfamily, we asked whether related species shared similar sound features. We found considerable overlap between sound characteristics of different vocalising species, suggesting a shared mechanism overall. However, distinct differences were also noted between families, suggesting that vocalisation may have evolved multiple times within Bombycoidea. The evolutionary origins and specific functions of vocalisation in caterpillars are discussed.

Sparse unscaled time-frequency transform and its application on seismic attenuation delineation

Seismic attenuation can be qualitatively delineated by the difference between low- and high-frequency components before and after attenuation. Time-frequency (TF) transform is a useful tool that is commonly used in the characterization of frequency component changes caused by seismic attenuation, in which the representative S-transform (ST) often is used for solving this issue. However, ST has a fixed TF localization and a significant frequency shift issue, leading to low resolution and accuracy of the results when used for qualitative attenuation estimation. To solve these issues, this study introduces an unscaled generalized ST (UGST) based on the unscaled ST to avoid the dominant frequency shift and achieve flexible adjustment of the TF localization. To further improve the resolution of TF, the solution of UGST is regarded as a convex optimization process with [Formula: see text]-[Formula: see text]-norm joint constraints, and the sparse UGST (SUGST) is solved by using the Bregman iterative algorithm. Synthetic experiments indicate that SUGST has high TF resolution and dominant frequency fidelity. Qualitative attenuation delineations of synthetic and field data are consistent with the synthetic model and reservoir interpretation. Its resolution and accuracy also are better than contrast methods, which further demonstrate the validity and advantage of the SUGST-based workflow in seismic attenuation delineation and reservoir interpretation.

Information theory-based direct causality measure to assess cardiac fibrillation dynamics.

Understanding the mechanism sustaining cardiac fibrillation can facilitate the personalization of treatment. Granger causality analysis can be used to determine the existence of a hierarchical fibrillation mechanism that is more amenable to ablation treatment in cardiac time-series data. Conventional Granger causality based on linear predictability may fail if the assumption is not met or given sparsely sampled, high-dimensional data. More recently developed information theory-based causality measures could potentially provide a more accurate estimate of the nonlinear coupling. However, despite their successful application to linear and nonlinear physical systems, their use is not known in the clinical field. Partial mutual information from mixed embedding (PMIME) was implemented to identify the direct coupling of cardiac electrophysiology signals. We show that PMIME requires less data and is more robust to extrinsic confounding factors. The algorithms were then extended for efficient characterization of fibrillation organization and hierarchy using clinical high-dimensional data. We show that PMIME network measures correlate well with the spatio-temporal organization of fibrillation and demonstrated that hierarchical type of fibrillation and drivers could be identified in a subset of ventricular fibrillation patients, such that regions of high hierarchy are associated with high dominant frequency.

A new species of the genus Leptobrachella Smith 1925 (Amphibia, Anura, Megophryidae) from Guangxi, China.

A new species of Leptobrachella, L.wumingensissp. nov., was described from the Damingshan National Nature Reserve, Wuming District, Nanning City, Guangxi, China based on morphological, molecular and bioacoustic data. Phylogenetic analysis of 16S mtDNA fragments revealed that the new species is closely related to L.damingshanensis. Uncorrected p-distances between the new species and all homologous DNA sequences available for the 16S gene of Leptobrachella are greater than 7.1%. Morphologically, L.wumingensissp. nov. differs from its congeners in several ways, including a medium body size (SVL 26.0-26.7 mm in males, 30.6-34.8 mm in females), lack of toe webbing and lateral fringes, shagreened and granular dorsal surface, pale brown dorsum with darker brown markings, iris bicolored, with the upper half copper and fading to silver in the lower half, and the presence of small irregular black spots and tangerine tubercles on the flanks. Furthermore, we found the new species to have two types of advertisement calls and relatively high dominant frequencies, making it distinct from its congeners.

Differences in male calling song and female mate location behaviour between urban and rural crickets

Abstract Traffic noise is one of the selection pressures of urban habitats. Because noise interferes with acoustic communication, many studies have shown that the temporal structures of acoustic signals change depending on the noise. However, it is often unknown whether the changes are adaptive, such as changes being more easily located by females under noisy conditions. To investigate the phenomena, bend-legged ground crickets (Dianemobius nigrofasciatus) were collected from three urban and three rural habitats and reared in a common garden conditions. Male calling songs and female mate location behaviour of the progeny were measured. Urban males emitted a calling song with a higher dominant frequency and shorter chirp than did rural males. The playback experiment of female response and localization to songs of urban and rural males, controlling for noise, showed that there were no significant effects of the song on the mate location behaviour between urban and rural songs under noisy conditions. Although the song of urban males elicited a faster response of females, the effect was limited. These results indicate the change in song is not adaptive in terms of female choice. Urban females located more quickly to song under noisy conditions. The results suggest adaptive changes in female mating behaviour occur in urban habitats.

Recovery of Ceratophrys ornata tadpoles exposed to environmental concentrations of chlorpyrifos: evaluation of biomarkers of exposure.

Chlorpyrifos (CPF) is one of the most widely used insecticides worldwide despite the fact that many authors have warned about its effects in non-target biota. The effects of CPF on anurans are well known, but the process of recovery from these effects after exposure is less explored. The aim of this study was to evaluate the duration of sublethal effects induced by environmental concentrations of CPF on Ceratophrys ornata tadpoles after exposure. The experimental design consisted of an exposure phase (96 h) in which tadpoles were individually exposed to three concentrations of CPF (0, 0.01 and 0.02 mg CPF/L) and a post-exposure phase (72 h) in which exposed tadpoles were transferred to CPF-free media. Individuals that survived the exposure phase to CPF showed neither long-term lethal effects nor long-term swimming alterations and altered prey consumption after being transferred to CPF-free media. No morphological abnormalities were observed either. However, at the end of both phases, tadpoles emitted shorter sounds with a higher dominant frequency than the tadpoles in the control group, i.e., the tadpoles did not recover their normal sounds. Thus, for the first time in this species, we have shown that effects on sounds should be prioritized as biomarkers of exposure, as they not only provide longer detection times after cessation of exposure, but also involve non-destructive methods. The following order of priority could be established for the selection of biomarkers that diagnose the health status of individuals and precede irreversible responses such as mortality: alterations in sounds > swimming alterations > prey consumption.

The relationship between high dominant frequency and low voltage areas in patients with atrial fibrillation: digital twin study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): a grant [2022R1I1A1A0106342211] from the Basic Science Research Program run by the National Research Foundation of Korea (NRF) which is funded by the Ministry of Science, ICT & Future Planning (MSIP) Background It has been suggested that the high dominant frequency (DF) site plays an atrial fibrillation (AF) driver, but its relationship with the atrial substrate voltage map (Vm) in the entire chamber AF map has yet to be studied. We explored the relationship between the DF site during AF and Vm in the entire chamber maps by applying the human left atrial (LA) electroanatomical map (EAM) to the digital twin AF map. Methods We acquired LA substrate Vm (at sinus rhythm, >800 points bipolar electrograms) of 110 patients with persistent AF (male 72.7%, 58.7±9.8 years old) who underwent AF catheter ablation. We applied EAM to digital twins (0.4 million nodes), reflecting anatomy, histology, and electrophysiology. We evaluated the highest 10% DF areas for 6 sec after inducing virtual AF. The correlation between the highest 10% DF and the low Vm areas (<0.2mV) was evaluated in the LA region of 10 segments. Results The mean voltage of the entire LA area was 1.96±0.85 mV (2.19±0.82 mV extra-PV area, 1.33±0.93 mV PV area) in 110 patients. The correlation between low Vm and high DF areas was not significant in the entire LA (r=0.106, p<0.001), extra-PV (r=0.157, p<0.001), and PV (r=0.079, p=0.097) areas. In the LA 10 segment regional analysis, 72 patients (65.5%) showed the co-localization of the highest DF in the region with the lowest Vm, and 14 patients (12.7%) had the lowest Vm segment in the region with the highest DF. The mean voltage where high DF appeared was 0.69±1.35 mV, and the mean voltage of the region where high DF did not appear was 0.59±1.15 mV (p=0.171). Conclusion High DF site, a parameter representing a localized focal source, had statistically significant but very poor correlations with LA extra-PV voltage substrate in patients with persistent AF.

Experimental study on thermal fatigue damage and failure mechanisms of basalt exposed to high‐temperature treatments

AbstractUnderstanding the effects of thermal fatigue damage on the failure mechanisms of rocks is a key concern in underground engineering. The effects of high temperature on the physical–mechanical behaviors and the failure mechanism of basalt under uniaxial compression are investigated with a combination of acoustic emission (AE), computed tomography (CT), and scanning electron microscope (SEM). The high temperature heavily affects the physical–mechanical properties of basalt but has no effect on the mineral compositions. The evolution characteristics of inter‐event time function F(τ) and cumulative AE energy can be employed to characterize the fracture process of thermally damaged basalt. The damage mechanisms of thermal fatigue are attributed to the occurrence of intergranular cracks, intragranular cracks, and transgranular cracks and irregular holes within basalt. The failure mechanisms of basalt change from shear fracture to mixed tensile–shear fracture and finally to tensile fracture based on the statistical characteristics of low and high dominant frequencies.

Seismic ahead-prospecting based on deep learning of retrieving seismic wavefield

Unknown geology ahead of the tunnel boring machine (TBM) brings a large safety risk for tunnel construction. Seismic ahead-prospecting using TBM drilling noise as a source can achieve near-real-time detection, meeting the requirements of TBM rapid drilling. Seismic wavefield retrieval is the key data processing step for the efficient utilization of TBM drilling noise. The traditional solution is based on cross-correlation to extract reflected waves, but the reference waves remain in the result, disturbing the imaging and interpretation of the adverse geology. To solve this problem, the deep learning method was introduced in wavefield retrieval to improve the accuracy of geological prospecting. We trained a deep neural network (DNN) with its strong nonlinear mapping capability to transform seismic data from TBM drilling noise to data from the active source. The issue lies in its features for this specific tunnel task, including the decay of the seismic signal with time and the incomplete spatial correspondence. Thus, we improved a classical DNN with the time constraint as an additional input, and an additional pre-decoder to enlarge the receptive field. Additionally, a loss function weighted by the ground truth and time constraint is improved to achieve an accurate retrieval of the effective signal, considering the little effective information in tunnel data. Finally, the workflow of the proposed method was given, and a dataset designed with reference to the field case was employed to train the network. The proposed method accurately retrieved the reflection signal with higher dominant frequencies, which helped improve the accuracy of imaging. Numerical simulations and imaging on typical geological models show that the proposed method can suppress reference waves and get more accurate results with fewer artifacts. The proposed method has been applied in the Gaoligongshan Tunnel and imaged two abnormal zones, providing meaningful geological information for TBM drilling and tunnel construction.

Sensitivity analysis of seismic attributes parametrization to reduce misinterpretations: Applications to deepwater channel complexes

Geoscientists apply algorithms such as seismic attributes to better interpret depositional systems that enhance various aspects of the seismic data. However, they are limited by the original seismic amplitude or frequency content, data quality, and algorithm parameters considered.Additionally, our capacity to interpret depositional system architecture is limited by seismic resolution, which results in potential misinterpretations associated with the correct position of stratigraphic features. Resolution also sets a minimum thickness that can be observed in seismic data. This is particularly important as mapping reservoir architecture (geobody size, shape, and stacking patterns) in the subsurface is critical for exploring and producing hydrocarbons, CO2 storage, and geothermal resource development since it can define connectivity or compartmentalization of flow zones.To address these concerns, we investigated five synthetic seismic volumes from low to high-dominant frequencies of 15 Hz, 30 Hz, 60 Hz, 90 Hz, and 180 Hz based on an architectural model of an outcropping deepwater channelized slope system in the Magallanes Basin, Chile. We analyzed 1) how seismic bandwidth affects the resolution of stacked stratigraphic features (i.e., deepwater channel elements and Mass Transport Deposits (MTDs)) and their subsequent seismic interpretation, and 2) the effect of different seismic attributes commonly employed in channel interpretation on our data to understand the “mixing” or “vertical smearing” of stratigraphic features by comparing the seismic with the true geological model 3) we explored how the attributes’ parametrization affects the imaging of differently sized features by modifying the analysis window in each case from ± 2ms to ± 50 ms. Finally, 4) we evaluated the effect of different noise levels in the sensitivity analysis. Resultsshow that the “mixing” of events occurs mainly as a result of 1) the seismic bandwidth, 2) the algorithm used for each seismic attribute calculation, 3) the attribute vertical analysis window, and 4) the signal-to-noise ratio of the data. Broadband, higher frequency data, and small analysis windows provide clearer images of the stacked channels. In contrast, low-frequency data and larger analysis windows result in more mixing or “composite” appearances, affecting interpretations and net-to-gross estimates, especially in small-size stratigraphic features such as individual channel elements and Mass Transport Deposits (MTDs). Our observations warn of potential misinterpretations in applying default attributes to actual seismic data, especially in geometrical attributes and window-dependent ones. Recognizing these misinterpretations is paramount for reconstructing deepwater architecture (this study), sedimentary and structural studies for drilling locations, reserves estimation, and overall uncertainty assessment.

Characteristics of Vibration Velocity Signal Using Liquid Carbon Dioxide Rock-Breaking Technology

Liquid carbon dioxide rock-breaking (L-CDRB) is a new physical blasting technology. To study the characteristics of its vibration velocity, rock-breaking field tests were conducted using a new type of liquid CO2 fracturing tube. Comparisons were made between explosive blasting and L-CDRB in terms of the peak values, frequencies, and energy distributions of the generated vibration velocities. The results show that (1) for the same scaled charge, L-CDRB (vs. explosive blasting) produced a smaller peak, a lower dominant frequency, and simpler frequency components of vibration velocities than explosive blasting. (2) The dominant frequency and energy distribution were related to the total liquid CO2 filling quantity. Higher total filling quantities resulted in higher dominant frequencies, and the energy distribution shifted from a low to a high-frequency band.

Theoretical and experimental exploration on the combined mode I + III fracture toughness of shale using the edge-notched disk bending method with acoustic emission monitoring

The combined mode I + III fracture toughness of shale plays a significant role in the exploitation of shale gas. To investigate the combined mode I + III fracture characteristics of shale, the ENDB (edge-notched disk bending) fracture experiments with AE (acoustic emission) monitoring are implemented to accomplish the full range of fractures from pure mode I (tension) to pure mode III (tearing). By considering the contribution of the mean strain energy to the onset of fracturing, this work develops the 3D-MSED (mean strain energy density) criterion. The measured results indicate that the fracturing energy of the ENDB shale increases linearly with the move from pure tension to pure tearing, while the effective fracture toughness for the ENDB shale decreases linearly. In comparison with the published 3D fracture criteria, the developed 3D-MSED criterion can predict an excellent combined mode I + III fracture toughness envelope for the ENDB shale. Interestingly, the Gaussian function can adequately describe the distribution of AE amplitudes, and the distribution discrepancy in AE amplitudes is insignificant for the ENDB shale specimens under different loading types. However, the percentage of the AE high dominant frequency for the tearing-dominated loading case is relatively greater than that of the tension-dominated loading case, and the tearing-dominated fracturing response is characterized by the nonplanar shear deformation.

High Dominant Frequencies and Fractionated Potentials Do Not Indicate Focal or Rotational Activation During AF

BackgroundDominant frequencies (DFs) or complex fractionated atrial electrograms (CFAEs), indicative of focal sources or rotational activation, are used to identify target sites for atrial fibrillation (AF) ablation in clinical studies, although the relationship among DF, CFAE, and activation patterns remains unclear. ObjectivesThis study sought to investigate the relationship between patterns of activation underlying DF and CFAE sites during AF. MethodsEpicardial high-resolution mapping of the right and left atrium including Bachmann’s bundle was performed in 71 participants. We identified the highest dominant frequency (DFmax) and highest degree of CFAE (CFAEmax) with the use of existing clinical criteria and classified patterns of activation as focal or rotational activation and smooth propagation, conduction block (CB), collision and remnant activity, and fibrillation potentials as single, double, or fractionated potentials containing, respectively, 1, 2, or 3 or more negative deflections. Relationships among activation patterns, DFmax, and potential types were investigated. ResultsDFmax were primarily located at the left atrioventricular groove and did not harbor focal activation (proportion focal waves: 0% [IQR: 0%-2%]). Compared with non-DFmax sites, DFmax were characterized by more frequent smooth propagation (22% [IQR: 7%-48%] vs 17% [IQR: 11%-24%]; P = 0.001), less frequent conduction block (69% [IQR: 51%-81%] vs 74% [IQR: 69%-78%]; P = 0.006), a higher proportion of single potentials (72% [IQR: 55%-84%] vs 6%1 [IQR: 55%-65%]; P = 0.003), and a lower proportion of fractionated potentials (4% [IQR: 1%-11%] vs 12% [IQR: 9%-15%]; P = 0.004). CFAEmax were mainly found at the pulmonary veins area, and only 1% [IQR: 0%-2%] of all CFAEmax contained focal activation. Compared with non-CFAEmax sites, CFAEmax sites were characterized by less frequent smooth propagation (1% [IQR: 0%-1%] vs 17% [IQR: 12%-24%]; P < 0.001) and more frequent remnant activity (20% [IQR: 12%-29%] vs 8% [IQR: 5%-10%]; P < 0.001), and harbored predominantly fractionated potentials (52% [IQR: 43%-66%] vs 12% [IQR: 9%-14%]; P < 0.001). ConclusionsFocal or rotational patterns of activation were not consistently detected at DFmax domains and CFAEmax sites. These findings do not support the concept of targeting DFmax or CFAEmax according to existing criteria for AF ablation.

The smallest of its kind: Description of a new cryptic Amnirana species (Amphibia, Anura, Ranidae) from West African rainforests

The distribution of the White-Lipped Frog Amnirana albolabris was long assumed to extend from eastern-central to western African rainforests. However, recent molecular phylogenetic analyses revealed that this taxon likely represents several undescribed species. Because the name-bearing types were collected in Gabon, the distantly related West African populations clearly represent an undescribed species that partly occurs in sympatry with Amnirana fonensis. Based on an integrative taxonomic approach, including molecular, morphological, and acoustic data, we describe the 'albolabris' populations from the Upper Guinean Forest Zone as a new species, and redescribe the morphologically similar A. fonensis on the bases of a larger series of genotyped individuals, including the first known females. We also provide new biological information for A. fonensis, including their advertisement call, habitat, and reproductive data. The new species is sister to A. fonensis and the two species differ by 5.8% in the mitochondrial 16S ribosomal RNA gene. Morphologically, males of the new species are smaller and have relatively smaller humeral glands. Females of the new species seem to have shorter legs than A. fonensis. In comparison to A. fonensis, the advertisement call of the new species has a higher dominant frequency and more pronounced frequency modulation. The two species differ in their distribution and habitat preferences, as revealed by environmental niche modelling. Whereas the new species is restricted to the Upper Guinean forests and thus is a true lowland-rainforest inhabitant, A. fonensis lives predominantly in Guinean montane forests in the forest-savanna mosaic zone.

High-resolution spatiotemporal changes in dominant frequency and structural organization during persistent atrial fibrillation.

Analyze changes in frequency activity and structural organization that occur over time with persistent atrial fibrillation (AF). Little is known about the frequency characteristics of the epicardium during transition from paroxysmal to persistent AF. Accurate identification of areas of high dominant frequency (DF) is often hampered by limited spatial resolution. Improvements in electrode arrays provide high spatiotemporal resolution, allowing for characterization of the changes that occur during this transition. AF was induced in adult Yorkshire swine by atrial tachypacing. DF mapping was performed using personalized mapping arrays. Histological analysis and late gadolinium enhanced magnetic resonance imaging were performed to determine structural differences in fibrosis. The left atrial epicardium was associated with a significant increase in DF in persistent AF (6.5 ± 0.2 vs. 7.4 ± 0.5 Hz, P = 0.03). The organization index (OI) significantly decreased during persistent AF in both the left atria (0.3 ± 0.03 vs. 0.2 ± 0.03, P = 0.01) and right atria (0.33 ± 0.04 vs. 0.23 ± 0.02, P = 0.02). MRI analysis demonstrated increased ECV values in persistent AF (0.19 vs 0.34, paroxysmal vs persistent, P = 0.05). Tissue sections from the atria showed increase in fibrosis in pigs with persistent AF compared to paroxysmal AF. Staining demonstrated decreased myocardial fiber alignment and loss of anisotropy in persistent AF tissue. Changes in tissue organization and fibrosis are observed in the porcine model of persistent AF. Alterations in frequency activity and organization index can be captured with high resolution using flexible electrode arrays.

Filtering strategies of electrocardiographic imaging signals for stratification of atrial fibrillation patients

Background and objectiveElectrocardiographic imaging (ECGI) has been used for guiding atrial fibrillation (AF) ablation, identifying reentrant activity by phase analysis with promising results. The objective of this study is to identify the best post-processing configuration for reentrant activity detection that better differentiates AF patients with different prognoses after catheter ablation. MethodsECGI signals of 24 AF patients before pulmonary vein isolation (PVI) were recorded. Patients were classified based on recurrence 6 months after PVI. Reentrant metrics were compared using 3 types of post-processing: none, sinusoidal recomposition (SRC), and narrow band-pass filtering centered at the highest dominant frequency (NB HDF). Different thresholds for rotor duration were also compared (0.5, 1, and 1.5 turns). ResultsThe use of raw ECGI signals with a threshold of 1 turn presented the optimal processing to identify PVI-positive responders (p < 0.05). NB HDF showed a better ability to find statistical differences between patients than SRC. ConclusionAggressive filtering of AF ECGI signals does not improve rotor identification to predict PVI outcome. Restrictive rotor duration thresholds diminish patient stratification. This definition of a post-processing strategy that allows patient stratification can be used for the improvement of the standard of care for finding the best candidates for PVI.