Peak Frequency Research Articles

A study on active road noise control based on operational transfer path analysis and selective subband adaptive filtering

In the feedforward active road noise control (ARNC) system, the noise reduction performance relies on the correlation between the reference signals and the target noise signals. To achieve better noise reduction performance, the operational transfer path analysis (OTPA) model with singular value decomposition was proposed to separate the road noise component from the target noise. Combined with OTPA and multi-coherence sorting method (MCSM), simulation analysis and real vehicle tests under various speeds both showed that the system with optimized reference sensor set had better road noise reduction performance, especially at the peak frequencies. To further improve noise reduction performance and reduce computational load, a selective subband adaptive filtering (SSAF) algorithm was proposed to build an active road noise control model with optimized reference sensor set. Simulation results, employing real vehicle test data, showed that the proposed method further improved the noise reduction performance and effectively reduced the amount of computational load.

The Primate Cortical LFP Exhibits Multiple Spectral and Temporal Gradients and Widespread Task-Dependence During Visual Short-Term Memory.

Although cognitive functions are hypothesized to be mediated by synchronous neuronal interactions in multiple frequency bands among widely distributed cortical areas, we still lack a basic understanding of the distribution and task dependence of oscillatory activity across the cortical map. Here, we ask how the spectral and temporal properties of the local field potential (LFP) vary across the primate cerebral cortex, and how they are modulated during visual short-term memory. We measured the LFP from 55 cortical areas in two macaque monkeys while they performed a visual delayed match to sample task. Analysis of peak frequencies in the LFP power spectra reveals multiple discrete frequency bands between 3-80 Hz that differ between the two monkeys. The LFP power in each band, as well as the Sample Entropy, a measure of signal complexity, display distinct spatial gradients across the cortex that correlate with reported spine counts in layer 3 pyramidal neurons. Cortical areas can be robustly decoded using a small number of spectral and temporal parameters, and significant task dependent increases and decreases in spectral power occur in all cortical areas. These findings reveal pronounced, widespread and spatially organized gradients in the spectral and temporal activity of cortical areas. Task-dependent changes in cortical activity are globally distributed, even for a simple cognitive task.

Injectable ultrasonic sensor for wireless monitoring of intracranial signals.

Direct and precise monitoring of intracranial physiology holds immense importance in delineating injuries, prognostication and averting disease1. Wired clinical instruments thatuse percutaneous leads are accurate but aresusceptible to infection, patient mobility constraints and potential surgical complications during removal2. Wireless implantable devices provide greater operational freedom but include issues such as limited detection range, poor degradation and difficulty in size reduction in the human body3. Here we present an injectable, bioresorbable and wireless metastructured hydrogel (metagel) sensor for ultrasonic monitoring of intracranial signals. The metagel sensors are cubes 2 × 2 × 2 mm3in size that encompass both biodegradable and stimulus-responsive hydrogels and periodically aligned air columns with a specific acoustic reflection spectrum. Implanted into intracranial space with a puncture needle, the metagel deforms in response to physiological environmental changes, causing peak frequency shifts of reflected ultrasound waves that can be wirelessly measured by an external ultrasound probe. The metagel sensor can independently detect intracranial pressure, temperature, pH and flow rate, realize a detection depth of 10 cm and almost fully degrade within 18 weeks. Animal experiments on rats and pigs indicate promising multiparametric sensing performances on a par with conventional non-resorbable wired clinical benchmarks.

Evaluation of root zone soil moisture products over the Huai River basin

Abstract. Root zone soil moisture (RZSM) is critical for water resource management, drought monitoring and sub-seasonal flood climate prediction. While RZSM is not directly observable from space, several RZSM products are available and widely used at global and continental scales. This study conducts a comprehensive and quantitative evaluation of eight RZSM products using observations from 58 in situ soil moisture stations over the Huai River basin (HRB) in China. Attention is drawn to the potential factors that contribute to the uncertainties of model-based RZSM, including the errors in atmospheric forcing, vegetation parameterizations, soil properties and spatial scale mismatch. The results show that the Global Land Data Assimilation System Catchment Land Surface Model (GLDAS_CLSM) outperforms the other RZSM products with the highest correlation coefficient (R= 0.69) and the lowest unbiased root mean square error (ubRMSE = 0.018 m3 m−3), while SMOS Level 4 (L4) RZSM shows the worst performance among eight RZSM products. The RZSM products based on land surface models generally perform better in the wet season than in the dry season due to the enhanced ability to capture of the temporal dynamics of in situ observations in the wet season and the inertia of remaining high soil moisture values even in the dry season, while the SMOS L4 RZSM product, derived from SMOS L3 surface moisture (SSM) combined with an exponential filter method, performs better in the dry season due to the attenuated ground microwave radiation signal caused by the increased water vapour absorption and scattering in the wet season. The underestimated SMOS L3 SSM triggers the underestimation of RZSM in SMOS L4. The overestimated RZSM products based on land surface models could be associated with the overestimated precipitation amounts and frequency, the underestimated air temperature, and the underestimated ratio of transpiration to the total terrestrial evapotranspiration. In addition, the biased soil properties and flawed vegetation parameterizations affect the hydrothermal transport processes represented in different land surface models (LSMs) and lead to inaccurate soil moisture simulation. The scale mismatch between point and footprint also introduces representative errors. The comparison of frequency of normalized soil moisture between RZSM products and in situ observations indicates that the LSMs should focus on reducing the frequency of wet soil moisture, increasing the frequency of dry soil moisture and the ability to capture the frequency peak of soil moisture. The study provides some insights into how to improve the ability of land surface models to simulate the land surface states and fluxes by taking into account the issues mentioned above. Finally, these results can be extrapolated to other regions located in similar climate zones, as they share similar precipitation patterns that dominate the terrestrial water cycle.

Near Field Detection and Peak Frequency Metric for Substrate and Activation Mapping of Ventricular Arrhythmias in 2- and 3-Dimensional Circuits.

Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the EGM may improve correct near field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of near- and far field (FF) EGMs may delineate the 3-dimensional path of a VT circuit. A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared to manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. VT isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low voltage areas, late activating areas and deceleration zones in LD vs NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander-sites. Activation mapping with entrainment and/or VT termination with RF ablation confirmed critical sites. 18 patients with high-density VT activation and substrate maps (55.6% ischemic) were included. NF detection correctly located critical parts of the circuit in 77.7% of the cases compared to manually reviewed VT maps as reference. In substrate maps NF detection identified deceleration zones in 88.8% of cases which overlapped with FDcorr VT isthmus in 72.2% compared to 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus-sites from low voltage bystander-sites. Omnipolar voltage was significantly higher at isthmus-sites with longer EGM durations compared to low voltage bystander-sites. The NF algorithm may enable rapid high-density activation mapping of VT circuits in the near field of the mapped surface. Integrated assessment and combined analysis of near and far field EGMs could support characterisation of 3-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low voltage bystander sites in this cohort.

Invertebrate sounds from photic to mesophotic coral reefs reveal vertical stratification and diel diversity.

Although mesophotic coral ecosystems account for approximately 80% of coral reefs, they remain largely unexplored due to their challenging accessibility. The acoustic richness within reefs has led scientists to consider passive acoustic monitoring as a reliable method for studying both altiphotic and mesophotic coral reefs. We investigated the relationship between benthic invertebrate sounds (1.5-22.5kHz), depth, and benthic cover composition, key ecological factors that determine differences between altiphotic and mesophotic reefs. Diel patterns of snaps and peak frequencies were also explored at different depths to assess variations in biorhythms. Acoustic recorders were deployed at 20m, 60m, and 120m depths across six islands in French Polynesia. The results indicated that depth is the primary driver of differences in broadband transient sound (BTS) soundscapes, with sound intensity decreasing as depth increases. At 20-60m, sounds were louder at night. At 120m depth, benthic activity rhythms exhibited low or highly variable levels of diel variation, likely a consequence of reduced solar irradiation. On three islands, a peculiar peak in the number of BTS was observed every day between 7 and 9 PM at 120m, suggesting the presence of cyclic activities of a specific species. Our results support the existence of different invertebrate communities or distinct behaviors, particularly in deep mesophotic reefs. Overall, this study adds to the growing evidence supporting the use of passive acoustic monitoring to describe and understand ecological patterns in mesophotic reefs.

Geometry effects in Impact Echo Signals - why traditional time-frequency filtering fails to remove them

Impact Echo signals can sometimes contain a lot of noise, even though the wavelength of the investigated modes is in the order of the specimen thickness. A special type of noise signals are the so-called geometry effects. These effects occur when the lateral dimensions of the investigated structure are not much larger than its thickness. This study compares signals with and without geometry effects using various types of signal processing methods such as classical fast Fourier transform, short-time Fourier transform, and the continuous wavelet transform. Results show that signals without geometry effects have a much more stable resonance frequency, whereas the main frequency content in Impact Echo signals containing geometry effects typically oscillates between two or more discrete frequencies. As this oscillation lasts for the entirety of the signals, traditional time-frequency filters will likely not be capable to remove geometry effects from Impact Echo signals. Resonance frequencies in Impact Echo signals unaffected by geometry effects are much more stable, with no fluctuation or oscillation over time. By comparing time-frequency representations of signals obtained at the same spot with different impactors, it is observed that the peak frequency at the beginning of each signal is similar for all three measurements. This result suggests that, for signals heavily affected by geometry effects, the beginning of the signal, which is usually neglected during Impact Echo inspection, could provide useful information regarding the thickness of the inspected structure. Two ways of obtaining thickness information from the signal beginning are presented and results are compared using a dataset from a reference specimen: one method uses classical Fourier transform of the signal beginning and the other approach uses the maximum frequency determined from the continuous wavelet transform. The results for both approaches show that the Impact Echo signal beginning contains depth information, which could prove valuable for evaluations of noisy datasets.

Study on acoustic emission and local deformation characteristics of feldspar vein-intrusive metagabbro at different angles of splitting

Feldspar vein-intrusive metagabbro is a special geological structure, and different stress angles have an important influence on the fracture mode and deformation characteristics of metagabbro. A Brazilian splitting test on feldspar vein-intrusive metagabbro was performed using three distinct stress angles (0°, 45°, and 90°), and acoustic emission signals and strain characteristics were monitored synchronously during the test. The results showed that the damage pattern of the feldspar vein-intrusive metagabbro was related to the feldspar mineral perforation damage on the main rupture surface. With the increase in stress angle, the percentage of high peak frequency increased gradually. The phenomenon of strain lagging stress appeared in the rock samples before the peak damage. The feldspar minerals played a controlling role in the expansion of microcracks in the feldspar vein-intrusive metagabbro. Significant differences in the local deformation coordination of rocks under different stress angles were observed. The deformation coordination of rock samples with a stress angle of 0° was much lower than that of other rock samples. This study is of great significance for the understanding of the deformation and damage laws of similar geological structures and also provides an important theoretical basis for the stability of deep chambers.

Quantitative electroencephalography in cerebral amyloid angiopathy

ObjectiveWe investigated whether quantitative electroencephalography (qEEG) correlates with cognition and cortical superficial siderosis (cSS) in cerebral amyloid angiopathy. MethodsWe included patients with sporadic (sCAA) and hereditary Dutch-type CAA (D-CAA). Spectral measures and the phase lag index (PLI) were analyzed on qEEG. Cognition was assessed with the MoCA and cSS presence was scored on 3T-MRI. Linear regression analyses were performed to investigate these qEEG measures and cognition. Independent samples T-tests were used to analyze the qEEG measure differences between participants with and without cSS. ResultsWe included 92 participants (44 D-CAA; 48 sCAA). A lower average peak frequency (β[95 %CI] = 0.986[0.252–1.721]; P = 0.009) and a higher spectral ratio (β[95 %CI] = −0.918[−1.761–−0.075]; P = 0.033) on qEEG correlated with a lower MoCA score, irrespective of a history of symptomatic intracerebral hemorrhage (sICH). The PLI showed no correlation to the MoCA. qEEG slowing was not different in those with or without cSS. ConclusionsSpectral qEEG (but not PLI) reflects cognitive performance in patients with CAA with and without a history of sICH. We found no association between qEEG slowing and cSS. SignificanceqEEG could be a valuable biomarker, especially in challenging cognitive testing situations in CAA, and a potential predictive tool in future studies.

A large-scale neuronal network modelling study: Stimulus size modulates gamma oscillations in the primary visual cortex by long-range connections.

Stimulus size modulation of neuronal firing activity is a fundamental property of the primary visual cortex. Numerous biological experiments have shown that stimulus size modulation is affected by multiple factors at different spatiotemporal scales, but the exact pathways and mechanisms remain incompletely understood. In this paper, we establish a large-scale neuronal network model of primary visual cortex withlayer 2/3 to study how gamma oscillation properties are modulated by stimulus size and especially how long-range connections affect the modulation as realistic neuronal properties and spatial distributions of synaptic connections are considered. It is shown that long-range horizontal synaptic connections are sufficient to produce dimensional modulation of firing rates and gamma oscillations. In particular, with increasing grating stimulus size, the firing rate increases and then decreases, the peak frequency of gamma oscillations decreases and the spectral power increases. These are consistent with biological experimental observations. Furthermore, we explain in detail how the number and spatial distribution of long-range connections affect the size modulation of gamma oscillations by using the analysis of neuronal firing activity and synaptic current fluctuations. Our results provide a mechanism explanation for size modulation of gamma oscillations in the primary visual cortex and reveal the important and unique role played by long-range connections, which contributes to a deeper understanding of the cognitive function of gamma oscillations in visual cortex.

A statistical analysis method for significant wave height and spectral peak frequency considering the random and time-varying effects based on copula function and Bayesian inference

Random and time-varying effects are important factors for statistical analysis of wave characteristic variables, including the significant wave height and spectral peak frequency. This paper proposes a statistical analysis method for the accurate statistical analysis of the state of the ocean. Several common distributions are applied as candidates for describing a specific variable, denoted as the marginal distribution. The joint distribution for the wave characteristic variables is constructed using copula functions based on the marginal distributions. The probability and unknown parameters of the marginal distributions are then determined by fully Bayesian inference. The best-fitting marginal distribution is selected based on the posterior probabilities of the candidates. Then, unknown parameters of the candidate copula functions are estimated by maximum likelihood estimation. The best-fitting copula function is selected based on Akaike information criterion, root mean squared error and Nash Sutcliffe efficiency. The proposed method is verified using the National Data Buoy Center dataset for 2019. However, this dataset, collected from a network of almost 100 moored buoys and Coastal-Marine Automated Network (CMAN) stations, contains incomplete data. The results reveal that the best-fitting marginal distribution and copula function may vary with the month. The average and maximum values of the improved RMSE using the proposed method are only 0.0064 and 0.0187, respectively. This indicates the high accuracy of the proposed method for the statistical analysis of wave states even though missing some data.

Exploration of peak frequency mapping for ventricular tachycardia ablation. Identification of critical isthmus zones during substrate mapping

Abstract Background/Introduction The ability to classify and differentiate between near field and far-field components of intracardiac signals is a key element in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. Near Field algorithms based on omnipolar electrograms enable detection and automation of true localised signals providing unique insights into substrate characteristics. This novel feature identifies localised signal peak frequency (PF) which can be displayed across different voltage ranges. Purpose/Aims The significance of PF mapping in the context of VT ablation is limited and its utility in the identification of the critical diastolic isthmus zone (IZ) is not known. The aim of this study is to explore the utilisation of PF mapping during VT ablation and evaluate whether significant differences in PF occur within areas of interest and critical components of the VT circuit during substrate mapping. Methods All patients underwent VT ablation using the EnSite™ X mapping system with the HDGrid omnipolar mapping catheter. Only cases with both high density sinus rhythm (SR) substrate maps and VT activation maps with clear identification of the IZ were included. VT activation and propagation maps were generated and the diastolic IZ was superimposed onto the SR substrate map. PF analysis was performed retrospectively. Surface area, omnipolar voltage and PF of the maps were measured in the SR substrate maps and co-localised with the critical IZ of the VT circuit as identified in the VT activation maps. Analysis of PF was conducted across different voltage ranges: healthy myocardium (>1.5mV), scar (1.5-0.5mV) and dense scar (0.5-0.1mV). Sensitivity and specificity measurements were made within segments of the IZ and non-isthmus zones and depicted as ROC curves. Results 55 patients underwent VT ablation over a 12-month period, with a total of 18 fulfilling the inclusion criteria. Mean age was 70 (±12.5years) with an average ejection fraction of 36%. The overall PF of the SR substrate maps was 121.85±26.85 Hz, compared to 162.22±46.22Hz within the IZ (p=0.002). Within the low voltage scar region, the overall PF was 120.86±33.24Hz compared to 188.32±81.36Hz within the IZ (p=0.003). No significant difference in PF was observed within healthy myocardium (112.70±52.06 Hz) compared to components of the IZ within the >1.5mV range (157.61±136.11Hz), p=0.207. The AUC for PF within the overall substrate map and co-localisation with the IZ was 0.67, and 0.73 within low voltage zones (<1.5mV). Conclusions PF mapping may identify critical components of the VT circuit during SR substrate mapping and its utilisation may compliment established substrate mapping approaches. PF guided ablation strategies require further evaluation in future prospective studies.

Peak frequency can be effectively used to characterize atrial remodelling in atrial fibrillation

Abstract Introduction Characterizing atrial fibrillation (AF) substrate can guide ablation strategies, particularly as current efficacy leaves room for substantial improvement. Low voltage zones (LVZs) correlate with atrial fibrosis and scar and can independently predict AF recurrence. Ablation of these zones improves freedom from arrhythmia, but the chaotic nature of atrial excitation frequently results in overestimation of LVZs limiting accurate substrate identification. Purpose While omnipolar voltage (OV) mapping has emerged to address this issue by closely correlating with sinus rhythm (SR) voltage maps, our study builds upon this by investigating a novel parameter, peak frequency (PF), to further refine AF substrate characterization. Methods Patients undergoing catheter ablation for persistent AF were enrolled. OV maps and PF maps were created during AF while bipolar voltage (BV) maps were created in SR with atrial pacing at pacing intervals (PIs) of 600ms and 250ms. Areas were classified as fixed scar (consistent LVZs across all maps), functional remodelling (LVZs in AF OV and SR BV 250ms maps) and non-LVZs (normal voltage across all maps). PF was assessed in these areas and defined as the highest frequency detected in the electrogram. Results Among 20 patients, the average voltage in AF OV maps differed significantly from SR BV 600ms (0.49±0.76mV in AF OV vs. 1.12±0.97mV SR BV 600ms, p<0.001) but not SR BV 250ms maps (0.49±0.76mV in AF OV vs. 0.52±0.84mV SR BV 250ms, p=0.10). Comparing co-registered points, there was a significant difference between AF OV and SR BV 600ms maps (0.21±0.09mV, p<0.001) but not between AF OV and SR BV 250ms maps (0.06±0.04mV, p=0.10). These findings were also consistent with regards to the proportion of LA area occupied by LVZs (42.4±8.2% AF OV, 24.3±7.4% SR BV 600ms and 39.4±6.7% SR BV 250ms; p=0.001). AF OV maps thereby correlated better with SR BV 250ms maps hence representing both fixed scar and functional remodelling. PF values ≥244Hz were predictive of non-LVZs (OR 3.91, 95% CI 3.77-4.07,) with an AUC of 0.71. A PF of ≤214Hz was predictive of fixed scar (OR 17.67, 95% CI 16.82-18.56, p<0.001) with an AUC of 0.90. A PF between 215-236Hz was predictive of functional remodelling (OR 2.83, 95% CI 2.71-2.95, p<0.001) with an AUC of 0.60. The majority of LVZs identified exclusively in AF OV maps exhibited PFs akin to those in non-LVZs highlighting the ability of PF to pinpoint potential overestimations in LVZs. Conclusions PF mapping can effectively discern between areas of fixed scar, functional remodelling, and potential overestimation of LVZs. PF may enhance substrate characterization in AF utilising data solely from electrograms.Trial Design and Zone AssignmentPeak Frequency and Voltage Zones

Differentiation of high frequency near field versus far-field potentials in low voltage zones during sinus rhythm improves discrimination of local sites of termination during ventricular tachycardia

Abstract Background Ventricular tachycardia (VT) with structural heart disease (SHD) is often bad tolerated or presents with several inducible morphologies, this support mapping the arrhythmic substrate during sinus rhythm (SR). Poor discrimination between near-field (NF) and far-field (FF) electrogram (EGM) components in low voltage (LV) areas is the main limitation. The peak frequency (PF) associated with bipolar EGMs may distinguish NF from FF EGMs (Panel D). Objective To evaluate if PF combined with voltage mapping during SR enhances discrimination of the region of VT termination by radiofrequency application (RFa). Methods Bipolar activation and voltage maps were generated with a 16-pole grid catheter (HD Grid) during SR (Panel B). PF maps were retrospectively computed (Panel C). The maps were only analyzed if acute termination was achieved by focal RFa within a boundary diameter <1.5cm (Panel A). The mapped surface area (SA) was sub-regioned in termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the termination site and was allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder mapped SA. Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE were measured according to the %SA covered at different LV thresholds (0.1-1.0mV in increments of 0.1mV - Panel F). LV high PF (LVHF) areas at different PF cutoffs from 150Hz (LVHF150) to 300Hz (LVHF300) were also assessed. Results 15 patients with SHD and sustained monomorphic VT were enrolled. 4 had 5 VT’s terminated by 1.4±0.9 focal RF lesions (60-74 y/o, 3 ischemic). All termination sites were located in a LVHF region mapped during SR (Panels B,C,E). The T-ZONE occupied 0.41±0.33cm /92.75±13.31cm global SA and consisted of 15±10 EGM points/1432±337 global points. T-ZONE voltage during SR (0.50±0.32mV) was significantly lower vs. global voltage (2.01±0.69mV, P<0.001), while T-ZONE PF was higher (324±51Hz) vs. global (270±37Hz, P<0.001). ROC discrimination of the T-ZONE yielded AUC’s of 0.79-LV alone, 0.87- LVHF150, 0.91-LVHF200 (Delta +12.2% vs LV alone, Panel F), 0.85-LVHF250 and 0.77-LVHF300. At a 0.7mV cutoff, LVHF200 yielded a balanced SE/SP of 0.89/0.87 vs. LV alone (0.90/0.63). Conclusion Assessment of regions with LVHF during SR improves SP for discrimination of sites of VT termination compared to LV alone.TV near field

Peak frequency mapping usefulness and utilization for typical AVNRT ablation

Abstract Background Accurate identification of slow pathway for the AVNRT ablation is important to achieve successful result and avoid complications mainly AV nodal block. There were some developments to produce precise image to locate this such as identify low voltage bridge (LVB) using electro-anatomical mapping and visualization of direct slow pathway capture (DCSP). The peak frequency (PF) associated with bipolar EGMs is a novel parameter which may serve to distinguish near filed (NF) from far field (FF) electrocardiogram (EGM) components. This technique can be used to differentiate sub-components derived from high density mapping. Previous study suggested this mapping appears to assist in substrate differentiation, pathway localization, and contact assessment. However, this approach has been never evaluated clinically in AVNRT ablation Objective This study conducted to evaluate the usefulness and utilization of the peak frequency mapping to identify the slow pathway location. Method The study conducted in November to December 2023 where twenty consecutive patients with common AVNRT were included in the study. Regular bipolar voltage and activation maps were generated with a regular 4 mm tip catheter. Following this, peak frequency maps (PF) were computed online prior ablation and displayed on the activation map with shadowed areas where PF was <200 Hz (figure, left panel). Focal radiofrequency application (RFa) was directed to the areas of late activation (figure, left panel) and low frequency (figure, right panel) (LA-LF). Successful ablation reached if junctional rhythm was recorded during RFa and AVNRT was no longer inducible afterwards. Results Twenty patients (48 ±15 years, 75% female) were enrolled in the study. A late activation low frequency area of 0.92±0.48 cm2 was found in 18 of them. This study revealed that there was a difference between PF in the slow pathway area compared to the adjacent area where the mean PF at the slow pathway area was 175.5 ± 37.1 Hz (analysis per patient) and 170.1 ± 48.10 Hz (analysis per recording site) which was lower and differed significantly than the PF recorded at the adjacent atrial area (279.71 ± 28.11 Hz per patient, 279.91 ± 69.47 Hz per recording site) (P<0.0001). Following the mapping, RFa were successfully applied at these late activation low-frequency (LA-LF) area induced junctional rhythm in 17 patients. AVNRT was no longer inducible after the ablation in all 17 patients. Additional RFa were often given to reinforce the result (11 ± 9 RFa, 4.03 ± 3.35 min RFa time). Conclusion The peak frequency mapping could be performed to map the slow nodal pathway which is often located in an area of late activation and low frequency.

The evaluation of the efficacy of automated peak frequency annotation algorithm for the identification of critical isthmus of ventricular tachycardia and deceleration zones

Abstract Background Substrate modification techniques have widely been adopted due to hemodynamic instability and non-inducibility of clinical ventricular tachycardia (VT). Accurate annotation of local near field EGMs is paramount to better evaluate the ventricular substrate. Furthermore, annotation of late potentials (LP) necessitates substantial manual input and isochronal late activation mapping (ILAM) involves constant sensitivity adjustments, potentially affecting the accuracy of local ventricular signal representation. Objective This study aims to assess the utility of novel automated peak frequency (PF), which aims to determine near field local activity in low voltage regions in the prediction of the CI of scar related reentrant VTs. Furthermore, the effectiveness of automated PF annotation of near field EGMs to identify deceleration zone (DZ) during ILAM was also evaluated. Methods A total of 18 patients with scar-related VT were analyzed. In all patients, VT isthmuses were identified based on activation maps and acute termination achieved during radiofrequency ablation. Automated PF annotation using Ensite X system (Abbott) was retrospectively performed in all cases specifically in areas of low voltage with fractioned signals. The accuracy of applying the PF value and automated ILAM map for detecting VT isthmus was also assessed. Results Among the study group, 12 (66.7%) had ischemic cardiomyopathy, while 6 (33.3%) had nonischemic cardiomyopathy [3 (16.7%) with arrhythmogenic right ventricular cardiomyopathy, 2 (11.1%) with idiopathic dilated cardiomyopathy, and 1 (5.6%) with hypertrophic cardiomyopathy]. All identified isthmuses were located in areas exhibiting bipolar voltage below 0.5 mV and a PF of 250 Hz with fractionated EGMs Automated NF DZ annotation predicted the VT isthmus in 16/18 (88.9%) of the cases similar to the conventional ILAM with manual adjustment (88.9%). Conclusion Using high-density electroanatomical mapping with near field algorithm, a PF cutoff of 250 Hz accurately identified the low voltage regions to predict the CI of VT. In addition, automated annotation of EGMs during ILAM similarly identified the DZs compared with conventional last deflection algorithm with manual adjustments, which were colocalized with CI of VTs.

Localization of critical isthmus in left atrial macroreentrant tachycardias: insights from peak frequency mapping during sinus rhythm and coronary sinus pacing

Abstract Background Successful ablation of left atrium macroreentrant tachycardia (LAMRT) has advanced significantly, benefiting from an enhanced understanding of reentrant mechanisms and technological innovations. However, challenges like difficult inductions and the presence of multiple coexistent LAMRTs can complicate tachycardia mapping, potentially resulting in recurrences during follow-up. Consequently, there is a growing need for strategies that focus on pinpointing the critical isthmus of conduction (CIC) in LAMRT circuits outside of tachycardia episodes. Peak frequency (PF) mapping, with its ability to discern near-field (NF) from far-field (FF) electrograms (EGMs) in low voltage areas, emerges as a valuable tool for precisely identifying these critical isthmuses. Purpose This study aims to investigate whether the accurate identification of the CIC in LAMRT circuits is achievable through PF mapping during sinus rhythm or coronary sinus pacing. Methods Patients with sustained LAMRT undergoing radiofrequency (RF) ablation were enrolled. Utilizing a 16-pole grid catheter (HD-Grid), bipolar voltage and activation maps were generated during LAMRT. PF maps were retrospectively computed. Voltage, activation, and PF maps were also created during sinus rhythm and coronary sinus pacing (500 ms). Potential CICs (P-CICs) were defined as areas with low voltage (<0.2 mV) and high PF (>250 Hz), covering a surface area of <2 cm2 by adjusting the PF threshold above 250 Hz. Only instances of LAMRT terminated by focal RF lesions (boundary <1.5 cm diameter) were included. Confirmed CICs (C-CICs) were identified at sites where LAMRT termination occurred due to RF application. The localization of P-CICs found during LAMRT, sinus rhythm (SR), and coronary sinus pacing (CSP) mapping, in relation to that of CIC, was analyzed, considering them matching if separated by <10 mm. Results Twenty-four consecutive patients with 26 atrial tachycardias (ATs) were prospectively enrolled, including 18 LAMRTs (270±63 ms) terminated by 2.2±2.9 focal RF lesions after 9.4±8.2 sec of energy delivery. A P-CIC was consistently identified at the tachycardia termination site during LAMRT mapping, with a visual cutoffs discrimination score (1-5) of 4.1±0.7, a mean P-P voltage cutoff <0.22±0.09 mV, and a mean PF cutoff >330±67 Hz in all patients. Importantly, P-CICs found during SR and CSP mapping matched those found during LAMRT mapping in all patients (figure). Conclusion PF mapping demonstrates precision in identifying the critical isthmus in LAMRT circuits during actual tachycardia episodes. Notably, the consistent identification of the CIC through PF mapping during sinus rhythm or coronary sinus pacing exhibits a high correlation with findings during LAMRT mapping. This approach holds promising potential for reducing arrhythmia recurrences, especially in scenarios involving multiple or unmappable LAMRTs.

Validating peak frequency mapping for atrial far-field electrogram detection: insights from a pulmonary vein isolation model

Abstract Introduction Effective pulmonary vein isolation (PVI) is the cornerstone of AF ablation, and conduction block from the atrium to the pulmonary veins (PV) is the accepted method to demonstrate it. However, far-field electrograms may make challenging to establish whether PVI has been achieved. Purpose This study aimed to evaluate whether peak frequency (PF) mapping can effectively identify far-field electrograms in the superior PVs following a redo PVI procedure. Methods Left atrium and PV activation and voltage bipolar 3D electroanatomical maps were generated using a steerable catheter with a 16-grid-patterned electrode configuration (HD-Grid) during coronary sinus pacing, both before and after the redo PVI. PF maps were developed offline using specialized experimental software. Only reconnected superior PVs from the redo PVI procedure were included in the analysis. Results Twenty consecutive patients (mean age 63±12 years, 12 male) were prospectively enrolled in the study, with 15 presenting reconnected PVs after the redo PVI. Conduction gaps were identified in the superior PVs of 9 patients (7 in the left superior PV, 5 in the right superior PV). Following the redo PVI, both voltage (0.96±1.1 mV vs. 0.49±1.21, P<0.01) and PF (285±134 vs. 153±112 Hz, P<0.001) were significantly reduced in both superior PVs. This reduction was more prominent in the right superior PV (0.83±0.75 vs. 0.20±0.39 mV, 299±159 vs. 132±116 Hz) than in the left superior PV (1.08±1.32 vs. 0.83±1.67 mV, 272±105 vs. 178±101 Hz). High-voltage (>0.3 mV) electrograms remained prevalent in the right (12%) and left (37%) superior PVs after the redo PVI. However, high PF (>250 Hz) electrograms significantly decreased following PVI in both the right (64% before vs. 6% after PVI) and left (66% before vs. 22% after PVI) PVs. Only a small percentage (5.3% in the right PV and 12% in the left PV) of all electrograms exhibited both high voltage and high PF following the PVI (see figure). Conclusion PF mapping proves to be a valuable tool in distinguishing far-field electrograms from atrial activity in the PVs, offering additional insights to complement voltage mapping, particularly in the context of redo PVI procedures.

Resting state EEG relates to short- and long-term cognitive functioning after cardiac arrest

BackgroundApproximately half of cardiac arrest survivors have persistent cognitive impairment. Guidelines recommend early screening to identify patients at risk for cognitive impairment, but there is no consensus on the best screening method. We aimed to identify quantitative EEG measures relating with short- and long-term cognitive function after cardiac arrest for potential to cognitive outcome prediction. MethodsWe analyzed data from a prospective longitudinal multicenter cohort study designed to develop a prediction model for cognitive outcome after cardiac arrest. For the current analysis, we used twenty-minute EEG registrations from 80 patients around one week after cardiac arrest. We calculated power spectral density, normalized alpha-to-theta ratio (nATR), peak frequency, and center of gravity (CoG) of this peak frequency. We related these with global cognitive functioning (scores on the Montreal Cognitive Assessment (MoCA)) at one week, three and twelve months follow-up with multivariate mixed effect models, and with performance on standard neuropsychological examination at twelve months using Pearson correlation coefficients. ResultsEach individual EEG parameter related to MoCA at one week (βnATR = 7.36; P < 0.01; βpeak frequency = 1.73, P < 0.01; βCoG = -9.88, P < 0.01). The nATR also related with the MoCA at three months ((βnATR = 2.49; P 0.01). No EEG metrics significantly related to the MoCA score at twelve months. nATR and peak frequency related with memory performance at twelve months. Results were consistent in sensitivity analyses. ConclusionEarly resting-state EEG parameters relate with short-term global cognitive functioning and with memory function at one year after cardiac arrest. Additional predictive values in multimodal prediction models need further study.

Peak frequency mapping characteristics in patients with scar-related atypical atrial reentrant tachycardias; findings from a novel automated annotation algorithm to detect near field signals

Abstract Background Atypical atrial tachycardias are commonly encountered rhythm disorders especially in patients with atrial low-voltage areas mainly due to previous catheter ablations or surgery. The peak frequency (PF) analysis of bipolar EGMs is a novel automated annotation tool which is mainly based on differentiation of near field signals from far field signals. Purpose In this study, we aimed to evaluate the association between PF analysis of voltage maps in low-voltage zones with the critical isthmus and termination sites of ATs. Methods In this retrospective analysis, we included a total of 36 patients (7 with right AT, 25 left AT, 4 biatrial). Omnipolar maps of RA and LA were created during AT using Ensite X Mapping system and HD-Grid catheter. Normal voltage is defined as ≥ 0.5 mV, borderline 0.1-0.5 mV and scar &amp;lt;0.1 mV. Only patients with acute termination of tachycardia with RF ablation were included. The sites within the 10 mm radius from the tachycardia termination site with RF were analysed in terms of voltage characteristics and PF analysis. Results The mean age of the study population was 53±15. Among 36 patients a total of 46 activation maps were created and 44 reentrant ATs were mapped. (24 (54.6%) ATs were macroreentry, 17 (38.6%) ATs were localized reentry and 3 ATs (6.8%) were dual-loop reentry). The low-voltage (LV) zones comprised 31.5±20.6% and 24.5±12.6% of total LA and RA, respectively. All AT termination sites using radiofrequency energy were located within the LV zones having high frequency activity using 250 Hz as the cut-off. The sensitivity of LV-NF zones to predict termination sites of re-entry was 97.2%. Conclusion The PF analysis of atrial substrate in the vicinity of the termination site of re-entrant ATs demonstrated high frequency signals within the low voltage zones. Therefore, addition of PF analysis with emphasis over voltage mapping may refine critical sites of reentry in LV regions.