Interelectrode Distance Research Articles

Evaluation and assessment of clique arrangements for the estimation of omnipolar electrograms in high density electrode arrays: an experimental animal model study

High-density catheters combined with Orientation Independent Sensing (OIS) methods have emerged as a groundbreaking technology for cardiac substrate characterisation. In this study, we aim to assess the arrangements and constraints to reliably estimate the so-called omnipolar electrogram (oEGM). Performance was evaluated using an experimental animal model. Thirty-eight recordings from nine retrospective experiments on isolated perfused rabbit hearts with an epicardial HD multielectrode were used. We estimated oEGMs according to the classic triangular clique (4 possible orientations) and a novel cross-orientation clique arrangement. Furthermore, we tested the effects of interelectrode spacing from 1 to 4 mm. Performance was evaluated by means of several parameters that measured amplitude rejection ratios, electric field loop area, activation pulse width and morphology distortion. Most reliable oEGM estimations were obtained with cross-configurations and interelectrode spacings le 2 mm. Estimations from triangular cliques resulted in wider electric field loops and unreliable detection of the direction of the propagation wavefront. Moreover, increasing interelectrode distance resulted in increased pulse width and morphology distortion. The results prove that current oEGM estimation techniques are insufficiently accurate. This study opens a new standpoint for the design of new-generation HD catheters and mapping software.

Newly Developed Electrochemiluminescence Based on Bipolar Electrochemistry for Multiplex Biosensing Applications: A Consolidated Review.

Recently, there has been an upsurge in the extent to which electrochemiluminescence (ECL) working in synergy with bipolar electrochemistry (BPE) is being applied in simple biosensing devices, especially in a clinical setup. The key objective of this particular write-up is to present a consolidated review of ECL-BPE, providing a three-dimensional perspective incorporating its strengths, weaknesses, limitations, and potential applications as a biosensing technique. The review encapsulates critical insights into the latest and novel developments in the field of ECL-BPE, including innovative electrode designs and newly developed, novel luminophores and co-reactants employed in ECL-BPE systems, along with challenges, such as optimization of the interelectrode distance, electrode miniaturization and electrode surface modification for enhancing sensitivity and selectivity. Moreover, this consolidated review will provide an overview of the latest, novel applications and advances made in this field with a bias toward multiplex biosensing based on the past five years of research. The studies reviewed herein, indicate that the technology is rapidly advancing at an outstanding purse and has an immense potential to revolutionize the general field of biosensing. This perspective aims to stimulate innovative ideas and inspire researchers alike to incorporate some elements of ECL-BPE into their studies, thereby steering this field into previously unexplored domains that may lead to unexpected, interesting discoveries. For instance, the application of ECL-BPE in other challenging and complex sample matrices such as hair for bioanalytical purposes is currently an unexplored area. Of great significance, a substantial fraction of the content in this review article is based on content from research articles published between the years 2018 and 2023.

Factors affecting electrogram sensing in an insertable cardiac monitor: Insights from surface electrocardiogram mapping analysis

Fidelity of electrogram sensing may reduce false alerts from an insertable cardiac monitor (ICM). The purpose of this study was to assess the effect of vector length, implant angle, and patient factors on electrogram sensing using surface electrocardiogram (EKG) mapping. Twelve separate precordial single-lead surface EKGs were acquired from 150 participants at 2 interelectrode distances (75 and 45 mm), at 3 vector angles (vertical, oblique, and horizontal), and in 2 postures (upright and supine). A subset of 50 patients also received a clinically indicated ICM implant in 1:1 ratio (Reveal LINQ [Medtronic, Minneapolis, MN]/BIOMONITOR III [Biotronik, Berlin, Germany]). All EKGs and ICM electrograms were analyzed by blinded investigators using DigitizeIt software (V2.3.3, Braunschweig, Germany). The P-wave visibility threshold was set at >0.015 mV. Logistic regression was used to identify factors affecting P-wave amplitude. A total of 1800 tracings from 150 participants (44.5% female; median 59 years) were assessed. Median P and R waves were 45% and 53% larger with vector lengths of 75 and 45 mm, respectively (P < .001 for both). The oblique orientation yielded the best P- and R-wave sensing, while posture change did not affect P-wave amplitude. Mixed effects modeling found that visible P waves occur more frequently with a vector length of 75 mm than with 45 mm (86% vs 75%, respectively; P < .0001). A longer vector length improved both P-wave amplitude and visibility in all body mass index categories. There was a moderate correlation of P and R waves from the ICM electrograms to those from surface EKG recordings (ICC 0.74 and 0.80, respectively). Longer vector length and oblique implant angle yielded the best electrogram sensing and are relevant considerations for ICM implantation procedures.

Comparison of Circular and Rectangular-Shaped Electrodes for Electrical Impedance Myography Measurements on Human Upper Arms.

Electrical Impedance Myography (EIM) is a painless, noninvasive approach for assessing muscle conditions through the application of a high-frequency, low-intensity current to the muscle region of interest. However, besides muscle properties, EIM measurements vary significantly with changes in some other anatomical properties such as subcutaneous skin-fat (SF) thickness and muscle girth, as well as non-anatomical factors, such as ambient temperature, electrode shape, inter-electrode distance, etc. This study has been conducted to compare the effects of different electrode shapes in EIM experiments, and to propose an acceptable configuration that is less dependent on factors other than the cellular properties of the muscle. Initially, a finite element model with two different kinds of electrode shapes, namely, rectangular (the conventional shape) and circular (the proposed shape) was designed for a subcutaneous fat thickness ranging from 5 mm to 25 mm. The study concludes, based on the FEM study, that replacing the conventional electrodes with our proposed electrodes can decrease the variation in EIM parameters due to changes in skin-fat thickness by 31.92%. EIM experiments on human subjects with these two kinds of electrode shapes validate our finite element simulation results, and show that circular electrodes can improve EIM effectiveness significantly, irrespective of muscle shape variation.

Impact of a standardized pacing protocol on end point verification and first pass isolation using a multipolar pulsed-field ablation catheter for pulmonary vein isolation

Pulsed-field ablation (PFA) has emerged as a novel treatment strategy for patients with atrial fibrillation (AF) ( 1 Badertscher P, Weidlich S, Serban T, et al. Pulsed-field ablation versus single catheter high-power short-duration radiofrequency ablation for atrial fibrillation: procedural characteristics, myocardial injury and midterm outcomes. Heart Rhythm 2023. Google Scholar , 2 Reddy VY, Dukkipati SR, Neuzil P, al. Pulsed Field Ablation of Paroxysmal Atrial Fibrillation: 1-Year Outcomes of IMPULSE, PEFCAT, and PEFCAT II. JACC Clin Electrophysiol 2021; 7(5):614–627. Google Scholar ). In general, acute pulmonary vein isolation (PVI) may be confirmed by entrance and exit block ( 3 Duytschaever M. Meyer G de Acena M. et al. Lessons from dissociated pulmonary vein potentials: entry block implies exit block. Europace. 2013; 15: 805-812 Crossref PubMed Scopus (25) Google Scholar ). The penta-spline PFA catheter only provides larger electrodes and wider inter-electrode distance making such an assessment less reliable. Little is known about the required number of applications when using PFA as systematically assessed via exit block testing. Likewise, since close proximity of the PFA catheter to the PV ostium seems to be of importance ( 2 Reddy VY, Dukkipati SR, Neuzil P, al. Pulsed Field Ablation of Paroxysmal Atrial Fibrillation: 1-Year Outcomes of IMPULSE, PEFCAT, and PEFCAT II. JACC Clin Electrophysiol 2021; 7(5):614–627. Google Scholar ), catheter positioning might be optimized by pacing before the first PFA application and adjusting contact depending on the ability to capture atrial myocardium. Thus, our aim was to assess the number of PFA applications per PV until acute PVI was observed and to assess the impact of a standardized pacing protocol on first pass isolation (FPI) confirmed via electroanatomical mapping (EAM). We prospectively enrolled consecutive patients undergoing their first PVI. In brief, the PFA 31 mm Farawave© catheter (Boston Scientific, Marlborough, MA) was inserted into the left atrium via a single transseptal puncture. PVI was performed as described previously ( 2 Reddy VY, Dukkipati SR, Neuzil P, al. Pulsed Field Ablation of Paroxysmal Atrial Fibrillation: 1-Year Outcomes of IMPULSE, PEFCAT, and PEFCAT II. JACC Clin Electrophysiol 2021; 7(5):614–627. Google Scholar ). In group 1 no standardized pacing protocol was applied prior or after PVI. In group 2, pacing was performed prior to the first application across all five bipoles to assess proximity of the PFA catheter to the PV ostium. Entrance and exit block were then assessed after each PFA application per PV separately. PVI was subsequently confirmed via EAM. The study was approved by the local ethics committees and adhered to the Helsinki Declaration.

Study of the omnipolar EGM reconstruction for robustness against wavefront propagation in epicardial signals

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): National Research Program, Ministerio de Ciencia e Innovación, Spanish Government, Instituto de Salud Carlos III. Background Characterisation of electrophysiological substrate is commonly performed by examining cardiac tissue locally by using high-density (HD) arrays of equispaced electrodes – e.g. Advisor™ HD Grid Mapping Catheter, Sensor Enabled™ (SE). These allow creating activation maps of local tissue and substrate exploration. Recently, a novel operation mode arouse: the omnipole, which overcomes many limitations of bipolar and unipolar electrograms, as they are claimed to be orientation independent. Nevertheless, the current technique to reconstruct omnipolar EGMs has pitfalls as the estimation of some incidence angles of the propagation wavefront. We propose a novel reconstruction method to estimate omnipolar EGMs which overcomes the angle dependence weakness of the current one, providing a more robust EGM representation. We hypothesise that this technique will improve reconstruction of electrophysiological signals. Methods Prior electrophysiological experiments on isolated rabbit hearts were used [1], including recordings with a 128-electrode array 1mm apart over ventricular epicardium at 37ºC, with bipolar electrode stimulation. Four-electrodes cliques were designed from these experiments, with different inter-electrode distances as depicted in fig. 1A, reconstructing the current, and novel omnipolar configuration. Metrics to assess the quality of the EGM signals were designed, including the bipolar loop area, and the ratio of the bipolar components of the omnipole (ox and oy) – see fig. 1B. The bipoles were calculated from unipolar EGMs, the signal was corrected with the 45º offset in the cross, the propagation angle was then detected, and the local activation time (LAT) was estimated. Results In the bipole plots, it was observed that the morphology of the bipolar loop gets distorted with an increase in the interelectrode distance – thinner for distances &amp;lt;2mm. There is a direct relation between the areas in the bipolar loop and the inter-electrode distance (see fig. 2A). Furthermore, the values of the area in the cross are always comparable to the best performing triangular clique. For the ratio of bipoles, the relation is inversely to distance (see fig. 2B), similarly, the performance of the cross is comparable to the best performing triangular omnipole. Conclusion For reconstructing omnipolar EGMs, inter-electrode distances smaller than 2mm should be employed. Furthermore, if that condition is satisfied, the novel omnipolar reconstruction method proposed based on the cross configuration is more accurate and robust to wavefront propagation, given that the omnipolar EGM performs similarly or better than the best triangular configuration – and which triangle is fixed for the whole procedure, being the current reconstruction method less robust. Thus, a new standpoint to omnipolar reconstruction in high density electrode catheters is open, towards the design of new devices, and the practice in the clinic.

Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: a dual-center experience

Abstract Funding Acknowledgements Type of funding sources: None. Background The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. Objective we conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). Methods We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n=14) or recurrent VT (n=7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n=9). The associations of peak-to-peak maximum standard bipolar (BVc) and minibipolar (PentaRay, BVp) with microbipolar (BVμMax) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. Results BVμMax was moderately associated with both BVc (β=0.85, p&amp;lt;0.01) and BVp (β=0.56, p&amp;lt;0.01). BVμMax was 0.98 (95% CI, 0.93-1.04, p&amp;lt;0.01) mV larger than corresponding BVc, and 0.27 (95% CI, 0.16-0.37, p&amp;lt;0.01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm2, p&amp;lt;0.01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm2, p=0.03) regions in microbipolar maps compared to standard bipolar maps. At sites of VT termination (n=14), μBE were of higher amplitude (0.9 [0.8] mV versus 0.4 [0.2] mV, p&amp;lt;0.01), longer duration (117 [66] ms versus 74 [38] ms, p&amp;lt;0.01), and with greater number of peaks (4 [2] versus 2 [1], p&amp;lt;0.01) in sinus rhythm compared to BE. Conclusions Microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for catheter ablation.

Myeloperoxidase causes both arrhythmogenic structural and electrical remodelling in neonatal rat ventricular myocyte monolayers

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study was supported by Netherlands Organization for Health Research and Development Background Myeloperoxidase (MPO), an enzyme most abundantly expressed by neutrophils, is increased in the atrial tissue of AF patients and is associated with treatment failure. Moreover, MPO increases fibrosis and AF susceptibility in mouse atria. However, how MPO promotes AF has yet to be fully established. Purpose To investigate the role of MPO in electrophysiological and structural remodelling. Methods We incubated cultured neonatal rat ventricular myocyte (NRVM) monolayers with 1 μg/mL MPO or vehicle for 24 hours. We then performed electrophysiological mapping using an 8x8 multielectrode array (MEA) setup with 100 μm-sized electrodes and 700 μm inter-electrode distance (n=8 MPO, n=7 control) and recorded action potentials (AP) using a microelectrode during pacing. Additionally, we quantified the number of fibroblasts using vimentin staining (n=5/group) and the expression of extracellular matrix (ECM) genes (COL1A1, COL8A2, FN1, CTGF, TNC, THBS2, MMP2, MMP12) using qPCR (n=4/group). Multielectrode data were analyzed with custom-made software in MATLAB. Statistical analysis was performed in R. Data presented as median [interquartile range]. Results NRVM monolayers incubated with MPO were unresponsive to pacing (5/8 vs 0/7 control) or had a higher pacing threshold (1300 [1000-2500] vs 500 [400-600] μA) (p=0.02). The percent of excitable tissue was lower in the MPO than in the control group, and the propagation of spontaneous activations was slower and more heterogeneous (index: 5 [3.6-9.5] vs 2 [1.5-3], p=0.004). More fractionated electrograms were present in MPO than in the control (29 [25-40] vs 11 [4-23] electrodes per grid, p=0.02). Re-entry was observed in 3/8 MPO-incubated monolayers vs 0/7 controls. Intracellular recordings revealed a less negative resting membrane potential (-50 [-24- -52] vs -69 [-56- -79] mV, p=0.04) and lower AP upstroke velocity (4 [2.5-14] vs 26 [22-28] V/s, p=0.01) in MPO-incubated cardiomyocytes than in the control. Moreover, relative to the control, MPO significantly increased the number of fibroblasts (126 [120-128] vs 87 [70-106] cells/0.26 mm^2, p=0.02) and the expression of MMP12 (1.17 (fold-change), p=0.04), whereas a trend toward increase was observed for other ECM genes, such as COL8A2 (1.5 (fold change), p=0.1). Conclusion Incubation of NVRM with MPO results in depolarization of cardiomyocytes and an increase in the number of fibroblasts and ECM gene expression. Thereby, MPO increases conduction heterogeneity and susceptibility to re-entry.

Sono-alternating current-electro-Fenton process for the removal of color, COD and determination of power consumption from distillery industrial wastewater

In this study, a variety of electrochemical and advanced oxidation processes (AOPs), such as sono (US), US/hydrogen peroxide (H2O2), direct/alternating current-electro-Fenton (DCEF / ACEF), and sono-direct/alternating current-electro-Fenton (US + DCEF / US + ACEF) processes were compared in terms of their ability to remove a certain percentage of color and chemical oxygen demand (COD) from distillery industrial wastewater (DIW), as well as their impact on the amount of power required to treat the wastewater. According to experimental findings, the hybrid US + ACEF process produced complete color-100% and COD-100% removal efficiencies with a lower power consumption of 3.40kWhr m−3 than single like US, DCEF, ACEF processes, and hybrid US/H2O2 and US + DCEF processes. The consequences of significant operational parameters such as treatment time (30–210 min), sonication power (20–100 W) current density (0.1–0.6A dm−2), pH (1–5), COD concentration (1500–7500 mg L−1), inter-electrode distance (1–4 cm), H2O2 concentration (100–350 mg L−1), pulse duty cycle (0.14–1.00) and combination of electrode (Al/Fe, Al/Al, Fe/Fe, Fe/Al) on the % COD removal efficiency and power consumption of DIW were investigated by using hybrid US + ACEF process. The synergistic index and water recovery between US and ACEF process were also investigated and reported in this work. When compared to the other processes, the US + ACEF method is the most appropriate since it can be used effectively and efficiently to remove pollutants from wastewater and industrial effluent.

Computational modeling of endovascular peripheral nerve stimulation using a stent-mounted electrode array

Objective. Endovascular neuromodulation has attracted substantial interest in recent years as a minimally invasive approach to treat neurological disorders. In this study, we investigated with a computational model the feasibility of stimulating peripheral nerves with an endovascular stent-mounted electrode array. Approach. Anatomically realistic FEM models were constructed for the pudendal and vagal neurovascular bundles. The electromagnetic fields generated from electrical stimuli were computed using Sim4Life NEURON models to predict dynamic axonal responses. Main results. The models predict that the stimulation thresholds of the endovascular stent-electrode array configurations tested are comparable to that of ring electrodes and are dependent on the inter-electrode distance and orientation of the device. Arranging multiple electrodes along the longitudinal axis of the nerve lowers surface charge density without sacrificing axon recruitment, whereas arranging electrodes along the circumference of the blood vessel reduces the risk of misalignment but lowers axon recruitment. Significance. Overall, this study predicts that the endovascular stent-electrode array is a feasible stimulation option for peripheral nerves, and the electrode array can be flexibly optimized to achieve the lowest stimulation threshold.

TCAD Analysis of Leakage Current and Breakdown Voltage in Small Pitch 3D Pixel Sensors.

Small-pitch 3D pixel sensors have been developed to equip the innermost layers of the ATLAS and CMS tracker upgrades at the High Luminosity LHC. They feature 50 × 50 and 25 × 100 μm2 geometries and are fabricated on p-type Si-Si Direct Wafer Bonded substrates of 150 μm active thickness with a single-sided process. Due to the short inter-electrode distance, charge trapping effects are strongly mitigated, making these sensors extremely radiation hard. Results from beam test measurements of 3D pixel modules irradiated at large fluences (1016neq/cm2) indeed demonstrated high efficiency at maximum bias voltages of the order of 150 V. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, meaning that premature electrical breakdown due to impact ionization is a concern. In this study, TCAD simulations incorporating advanced surface and bulk damage models are used to investigate the leakage current and breakdown behavior of these sensors. Simulations are compared with measured characteristics of 3D diodes irradiated with neutrons at fluences up to 1.5 × 1016neq/cm2. The dependence of the breakdown voltage on geometrical parameters (e.g., the n+ column radius and the gap between the n+ column tip and the highly doped p++ handle wafer) is also discussed for optimization purposes.

Toward noninvasive monitoring of plant leaf water content by electrical impedance spectroscopy

Plant water content is one key factor that affects the wellbeing of plants. Furthermore, detecting plant water needs in a timely manner is important when considering irrigation strategies (water management). A first step toward plant water monitoring is the availability of a portable and cost-effective system that yields reliable information. Electrical impedance spectroscopy (EIS) has previously been used invasively to provide such data and can be implemented at an acceptable cost. In this work, a cost-effective impedance analyzer capable of performing noninvasive four-electrode measurements was built. In addition, data fitting has been improved by using a modified equivalent circuit model, yielding relevant information about the plant water status. The results show that the resistor that models the extracellular fluid can track the change in the water content of a plant leaf while it is drying at room temperature. On the other hand, impedance data might provide information about the leaf tissue structure at small interelectrode distances.

Titanium dioxide effect on the decolourisation of organic dyes Remazol Black B using electrocoagulation in situ-Fe2O3

ABSTRACT In this research, combination of TiO2 pillared clay with electrocoagulation in situ-Fe2O3 provides excellent performance to remove dyes water waste Remazol Black B(RBB). The best TiO2:clay ratio is 1:6, with highest degradation performance 89.8% in 30 minutes photodegradation process under UV light 254 nm. The excellent performance of pillared clay causes mesoporous pore that can be achieved by pillarisation of the clay layer using titanium dioxide sol which was made by diluting TiCl4 in ethanol solution. Besides, the excellent electrocoagulation performance was conducted by dual compartment system using 10ppm of RBB in the alkaline system containing 1 g NaCl as an electrolyte at potential apply+6 V with 98% degradation efficiency in 3 hours running compared to the 78% in single compartment system towards the formation of in situ-Fe2O3 that is directly driven by formation of intermediate species Fe(OH)3. This optimum decolourisation efficiency was gained at 0.1 A, pH 7.2 and 2 cm of inter-electrode distance. The power consumption was very low with the excellent and fast degradation performance towards organic dyes Remazol Black B, where this tandem cell can produce 100 mL clean water using 0.0052 kWh energy with cheaper cost operation.

Structural Regulation of Mechanical Gating in Molecular Junctions

In contrast to silicon-based transistors, single-molecule junctions can be gated by simple mechanical means. Specifically, charge can be transferred between the junction's electrodes and its molecular bridge when the interelectrode distance is modified, leading to variations in the electronic transport properties of the junction. While this effect has been studied extensively, the influence of the molecular orientation on mechanical gating has not been addressed, despite its potential influence on the gating effectiveness. Here, we show that the same molecular junction can experience either clear mechanical gating or none, depending on the molecular orientation in the junctions. The effect is found in silver-ferrocene-silver break junctions and analyzed in view of ab initio and transport calculations, where the influence of the molecular orbital geometry on charge transfer to or from the molecule is revealed. The molecular orientation is thus a new degree of freedom that can be used to optimize mechanically gated molecular junctions.

PO-02-152 EFFECTS OF SYMPATHETIC STIMULATION ON REPOLARIZATION AND ARRHYTHMOGENESIS DURING LEFT LATERAL MYOCARDIAL ISCHEMIA

Left stellate ganglion stimulation (LSGS) is arrhythmogenic during acute myocardial ischemia of the anterior wall of the left ventricle. We hypothesized, as a counterpart, that right stellate ganglion stimulation (RSGS) is proarrhythmic when ischemia is produced by occlusion of the circumflex coronary artery. In 7 anesthetized female open-chested pigs, ventricular repolarization was measured in unipolar electrograms from 128 epicardial sites on the left lateral ventricular wall in an electrode grid of 14x30 mm (interelectrode distance 2 mm). Seven subsequent episodes of 5 minutes of acute ischemia (5 minutes occlusion of the circumflex coronary artery with 20 minutes reperfusion). Right atrial pacing was performed throughout the experiment at cycle length of 450 ms. The second occlusion served as a control. During the third and fourth occlusion, left or right stellate ganglion stimulation (LSGS or RSGS), respectively, was initiated after 3 minutes of ischemia for 30 seconds. The protocol was repeated after decentralization of both stellate ganglia and bilateral cervical vagotomy. Between 3 and 5 minutes of ischemia, RSGS caused a median of 9 (interquartile range 3-12), ventricular premature beats and in 2 instances ventricular tachycardia and fibrillation. The number of ventricular premature beats was significantly less during LSGS and control conditions (Figure, panel A), during which no ventricular tachycardia or fibrillation occurred. Following decentralization, RSGS was no longer significantly more arrhythmogenic than LSGS or control conditions (Figure, panel A). Additionally, we found that LSGS-induced changes in repolarization are evident in non-ischemic tissue, but not in ischemic tissue, during coronary occlusion (Figure, panel B, note the overlapping T-waves in the ischemic region). LSGS no longer has an effect on myocardium that has been ischemic for 3 minutes by occlusion of the circumflex coronary artery. RSGS was arrhythmogenic in this setting, while LSGS was not. This supports the clinical findings that bilateral sympathectomy is superior to left sympathectomy alone.

PO-01-142 ACUTE ATRIAL DILATION INCREASES REFRACTORY PERIOD AND CONDUCTION ABNORMALITIES: EVIDENCE FROM IN-VIVO MAPPING AND IN-VITRO LIVING ATRIAL SLICES

Atrial dilation shows strong clinical association with atrial fibrillation (AF) and its proarrhythmic nature is confirmed by various studies. However, previous (animal) models reproducing acute dilation yielded in conflicting effects on the functional refractory period (FRP). Shortcomings of previous studies included lack of in-human measurements, high-density mapping, atrial conduction characterization and titration of dilation. To evaluate the effect of acute atrial dilation on human atrial refractoriness and conduction with a two-way approach of in-vivo high-density mapping and in-vitro living atrial slices. Epicardial mapping with a 192-electrode array (inter-electrode distance 2.0 mm) was performed in 4 patients undergoing mitral valve surgery, without history of right atrial (RA) dilation and AF. Mapping was performed on the mid RA during baseline and overloaded conditions (echocardiographic RA diameter increase 10-20%) by positioning patients in Trendelenburg. Atrial FRP and conduction were evaluated with programmed extrastimulation, consisting of a S1-sequence with cycle length (CL) of 400ms followed by S2 stimuli of 300ms with decrements of 20ms. In addition, 23 living myocardial slices (LMS) (thickness: 300μm) were produced from RA left-over material from cardiac surgeries and cultured under electromechanical stimulation (diastolic preload 1mN, electrical stimulation 1.0Hz). These LMS were overloaded with 10–40% extra uniaxial lengthening for evaluation of FRP and early aftercontractions (EAC). FRP significantly increased during acute dilation both in in-vitro LMS (211±49 vs. 271±34ms, p=0.01) and during in-vivo electrophysiological mapping (255±30 vs. 280±23ms, p=0.042). FRP further increased with increasing dilation and EAC were more present in dilated LMS (Table 1). During acute dilation, S2 pacing (CL: 300ms) resulted in an increase in total activation time (TAT) (31 (29–39) vs. 67 (49–82) ms), conduction block (0.6 (0.0–3.0) vs. 12.9 (8.4-16.7)%) and total length of conduction block (2 (0–9) vs. 48 (21–72) mm). Moreover, the S2 stimulus with shortest coupling interval showed even more abnormalities in atrial conduction during dilation compared to baseline (Table 1). This first in-human study showed an unambiguous increase in atrial FRP and frequency-dependent conduction abnormalities during acute atrial dilation. These observations provide novel insights in the enhanced vulnerability for the development of AF in patients with dilated atria.Tabled 1Table 1In-vivo: EP mappingBaselineDilationRA Ø (cm)4.6 ± 1.05.6 ± 1.2CVP (mmHg)8 ± 418 ± 8FRP (ms)255 ± 30280 ± 23S1 400 msTAT (ms)34 (32 – 41)44 (40 – 52)CV (cm/s)85.5 (81.1 – 86.1)80.9 (77.7 – 83.8)CB (%)1.5 (1.1 – 2.1)3.1 (1.7 – 4.4)Length CB (mm)7 (5 – 9)16 (9 – 22)S2 300 msTAT (ms)31 (29 – 39)67 (49 – 82)CV (cm/s)82.1 (75.3 – 86.0)68.9 (61.6 – 79.8)CB (%)0.6 (0.0 – 3.0)11.7 (5.6 – 16.7)Length CB (mm)2 (0 – 9)48 (21 – 72)S2 with shortest coupling intervalTAT (ms)49 (41 – 61)82 (75 – 84)CV (cm/s)72.2 (67.0 – 78.3)66.7 (61.6 – 73.2)CB (%)6.0 (2.9 – 11.3)12.9 (8.4 – 16.7)Length CB (mm)30 (11 – 49)53 (33 – 72)In-vitro: LMSBaselineDilationAcute 20% (n=10)FRP (ms)211 ± 49271 ± 34EAC (%)0%50%Titration (n=13)10%20%30%40%FRP (ms)241 ± 46263 ± 68278 ± 63297 ± 75330 ± 79 Open table in a new tab

PO-01-231 IDENTIFICATION OF ATRIAL ENDO-EPICARDIAL ASYNCHRONY USING SIGNAL FINGERPRINTING

Atrial three-dimensional (3D) dissociation in conduction facilitates the development of atrial fibrillation (AF). Previous mapping studies revealed that patients with persistent AF have more endo-epicardial asynchrony (EEA) during SR than those without AF. Areas of EEA can be accurately identified by using unipolar electrograms (EGM). Alterations in endo-epicardial unipolar EGM features within EEA areas may provide novel insight into the electrical substrate of AF. To develop a novel method for estimating the degree of EEA by using unipolar EGM characteristics recorded from either the endo- and/or epicardium. During SR, intra-operative simultaneous endo-epicardial mapping (256 electrodes, 2 mm interelectrode distance) of the right atrium was performed in 86 patients. EEA was defined as an endo-epicardial dissociation exceeding 15 ms. EGM features, including voltages, low voltage areas (LVAs, <1.0 mV), potential types (single, short/long double and fractionated potentials) and fractionation duration (FD) were analyzed and correlated to EEA areas. The Asynchrony Fingerprinting Score (AFS) was developed based on uni- and multivariable logistic regression analyses. Three AFSs (Epi-AFS, Endo-AFS and EE-AFS) were established and assessed. EEA areas were characterized by a decrease in potential voltages, an increase in the number of long double potentials (LDPs) and fractionated potentials (FPs) and prolongation of double potentials (DPs) and FPs compared to non-EEA areas. Epi-AFS contained epicardial median voltage and the proportion of LDP, whereas the Endo-AFS contained the endocardial proportion of LVAs and single potentials (SPs). The EE-AFS, containing the proportion of endocardial LVAs, and the FD of epicardial DPs, showed the highest predictive value (AUC: 0.913) in determining the degree of EEA, although both Epi- and Endo-AFS also showed good predictive value with AUCs of 0.830 and 0.901 respectively. EEA is characterized by increased amounts of LVAs, LDPs and FPs, as well as an increase in the duration of both DPs and FPs. Epi-, Endo- and EE-AFS all showed good accuracy in identifying EEA areas. Therefore, AFS, as a novel approach utilizing integrated data from endo- or/and epicardium, may enable precise identification of EEA degree, including potentially arrhythmogenic substrates.

PO-03-097 DEFINING ELECTRODE CONFIGURATION FOR MAPPING MICROANATOMIC REENTRIES SUSTAINING ATRIAL FIBRILLATION

A major challenge in mapping atrial fibrillation (AF) to guide ablation is that it is unclear what resolution is required to map potential regions of interest such as those microanatomic reentries revealed by optical mapping of ex-vivo human hearts (fig. A). The goal of the study was to define the electrode configurations that can identify potential ablation targets as specific EGM traces generated during the conduction through the common path of AF microanatomic reentry. We simulated a microanatomic reentry sustaining AF in anisotropic 3D model of atrial tissue of 40x40x3 mm with an endocardial pectinate muscle of 3x3x15 mm (0.25 mm resolution, fig. B), using Koivumäki-cellular model of human atrial action potential. The simulation also included recordings of endocardial unipolar and bipolar electrodes (3 mm inter-electrode distance, 1 mm length, 2 mm diameter) with different distances and orientations from the pectinate muscle (fig. B). Local activation time map (fig. C) of the simulation showed sub-endocardial microanatomic reentry, with the common path through the pectinate muscle with a cycle length of 110 ms. The electrical activation through the pectinate muscle and atrial wall below the electrodes (Fig. D) was compared to the simulated EGM traces at different distances from the common path (fig. E). On EGMs close to the pectinate muscle (<2mm) electrical activity of reentrant common path can be identified in both unipolar and bipolar EGM signals by peak with amplitude similar or larger than the main atrial wall activation (figs E-F). When bipolar electrodes were perpendicular to the pectinate muscle, the peak amplitude of the common path activity was lower than 25% of the atrial wall peak amplitude. Our simulation suggested that inter-electrode distance to detect sub-endocardial microanatomic reentries sustaining AF should be < 4mm. Mapping was more reproducible for unipolar than for bipolar mapping, as bipolar electrodes were highly sensitive to orientation relative to the common path conduction.

First review of capacitance-based self-sensing in structural materials

This is the first review of the emerging field of capacitance-based self-sensing in structural materials. Capacitance-based self-sensing is rich in both science and applications. It is applicable to materials ranging from insulators to conductors, whereas the longstanding resistance-based self-sensing is only applicable to conductors. The attributes sensed include the stress/strain, temperature and damage. The stress/strain sensing exploits piezopermittivity, which is typically positive. The temperature sensing exploits pyropermittivity, which is typically positive. The damage sensing exploits the fact that defects reduce the permittivity. The dielectric behavior of highly conductive materials is consistent with the 1999 theoretical prediction by Jonscher concerning charge-carrier polarization and the consequent “giant polarizability”. The materials for which capacitance-based self-sensing has been shown include 3D-printed polymer, asphalt (bitumen-based material), cement-based materials (without or with conductive admixture), continuous carbon fiber polymer-matrix composite, carbon-carbon composite, steel and aluminum. For the conductors, the polarization hinges on the carrier-atom interaction. For the electronic conductors (carbons and metals), the carriers are electrons. For the ionic conductors (cement-based material without conductive admixture), the carriers are ions. For the nonconductors (3D-printed polymer and asphalt), the molecules present align to cause polarization. This work is focused on the ordinary frequencies (such as kHz). For the conductors, the capacitance measurement using an LCR meter needs to be performed with a dielectric film between the specimen and an electrode. For determining the permittivity, the capacitance should be measured for three or more different values of the inter-electrode distance, so that the specimen volumetric capacitance and the interfacial capacitance of the specimen-electrode interface are decoupled.

Evaluation of Novel Embroidered Textile-Electrodes Made from Hybrid Polyamide Conductive Threads for Surface EMG Sensing.

Recently, there has been an increase in the number of reports on textile-based dry electrodes that can detect biopotentials without the need for electrolytic gels. However, these textile electrodes have a higher electrode skin interface impedance due to the improper contact between the skin and the electrode, diminishing the reliability and repeatability of the sensor. To facilitate improved skin-electrode contact, the effects of load and holding contact pressure were monitored for an embroidered textile electrode composed of multifilament hybrid thread for its application as a surface electromyography (sEMG) sensor. The effect of the textile's inter-electrode distance and double layering of embroidery that increases the density of the conductive threads were studied. Electrodes embroidered onto an elastic strap were wrapped around the forearm with a hook and loop fastener and tested for their performance. Time domain features such as the Root Mean Square (RMS), Average Rectified Value (ARV), and Signal to Noise Ratio (SNR) were quantitatively monitored in relation to the contact pressure and load. Experiments were performed in triplicates, and the sEMG signal characteristics were observed for various loads (0, 2, 4, and 6 kg) and holding contact pressures (5, 10, and 20 mmHg). sEMG signals recorded with textile electrodes were comparable in amplitude to those recorded using typical Ag/AgCl electrodes (28.45 dB recorded), while the signal-to-noise ratios were, 11.77, 19.60, 19.91, and 20.93 dB for the different loads, and 21.33, 23.34, and 17.45 dB for different holding pressures. The signal quality increased as the elastic strap was tightened further, but a pressure higher than 20 mmHg is not recommended because of the discomfort experienced by the subjects during data collection.