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Electrocardiographic imaging (ECGI) is a non-invasive technique that combines patient-specific cardiac anatomy with numerous body-surface potentials to gain insight into the in vivo electrical epicardial activity across the whole heart. This review summarises some of the latest hardware developments for ECGI data acquisition as well as innovative software solutions to address the inverse problem of electrocardiography. It delves into some of the successful clinical applications of ECGI while highlighting the hurdles that still stand in the way of its more widespread roll-out to healthcare. As well as serving as a powerful tool for electrophysiological research, ECGI promises to play an increasingly valuable role in the personalised diagnosis and management of cardiac arrhythmias.

On the dayside of the Moon, the surface potential is primarily determined by (a) photoelectron emission by solar radiation and (b) the ambient plasma environment. Both of these drivers have large variability, but the resulting variability of the lunar surface potential has not been fully characterized yet. To investigate the solar activity dependence of the dayside lunar surface potential in the terrestrial magnetotail, we compared long‐term observations of lunar surface photoelectrons with numerical calculations of photo‐emitted electron energy spectra. The comparison demonstrates that the observed solar activity dependence of lunar photoelectrons is well reproduced by the model. The current balance surface potential based on this model predicts more positive potentials for higher solar activities, possibly exceeding +100V${+}100\\ \\mathrm{V}$in the magnetotail lobes during solar flares. These results highlight the importance of evaluating the lunar electrostatic environment under various conditions, including extreme solar events.

Electrocardiography imaging (ECGi) is a non‐invasive inverse reconstruction procedure which employs body surface potential maps (BSPM) obtained from surface electrode array measurements to improve the spatial resolution and interpretability of conventional electrocardiography (ECG) for the diagnosis of cardiac dysfunction. ECGi currently lacks precision, which has prevented its adoption in clinical setups. The introduction of high‐density electrode arrays could increase ECGi reconstruction accuracy but is not attempted before due to manufacturing and processing limitations. Advances in multiple fields have now enabled the implementation of such arrays which poses questions on optimal array design parameters for ECGi. In this work, a novel conducting polymer electrode manufacturing process on flexible substrates is proposed to achieve high‐density, mm‐sized, conformable, long‐term, and easily attachable electrode arrays for BSPM with parameters optimally selected for ECGi applications. Temporal, spectral, and correlation analysis are performed on a prototype array demonstrating the validity of the chosen parameters and the feasibility of high‐density BSPM, paving the way for ECGi devices fit for clinical application. A high‐density conducting polymer electrode array for body surface potential mapping (BSPM) is proposed, with parameters optimally selected for electrocardiographic imaging (ECGi) applications. Temporal, spectral, and correlation analyses performed on prototype arrays confirm the optimal set of parameters and demonstrate the feasibility of high‐density BSPM, paving the way for ECGi devices fit for clinical application.

Background In addition to different types of single-tip ablation catheters for pulmonary vein (PV) reisolation, a newly developed circular mapping and ablation catheter (nMARQ ® ) has been available since 2013 and is currently used only in initial PV isolation procedures. In this prospective registry we present feasibility and efficacy data for PV reisolation procedures with a single-catheter approach (nMARQ ® ) compared with a standard approach using a single-tip ablation catheter and a circular mapping catheter. Methods We included 35 carefully selected patients in this prospective registry and assigned them in a 2:1 ratio to undergo either PV reisolation with a single-tip ablation catheter together with a steerable circular mapping catheter (group 1) or with the nMARQ ® catheter only (group 2). The recurrence rate was calculated for atrial tachyarrhythmias with a duration of > 30 s during a mean follow-up of 12.7 months. Results Reisolation of all PVs was achieved in all patients of both groups. In group 2, all gaps could be correctly identified with the nMARQ ® catheter. PV isolation was clearly visible on the nMARQ ® catheter in all targeted veins. With the nMARQ ® catheter the ablation time decreased significantly (6.3 ± 3.0 vs. 18.6 ± 13.9 min, p  < 0.05). The recurrence rate of atrial fibrillation did not differ significantly between the two groups (37.5 vs. 45.5 %, p  = 0.66). Conclusion In selected patients, a complete PV reisolation procedure is feasible with a singular circular mapping and ablation catheter. The 12-months success rate is comparable to a classic approach with a combination of a single-tip ablation catheter and a circular mapping catheter.

Background Pulsed field ablation (PFA) of atrial fibrillation (AF) using a pentaspline multi-electrode catheter is commonly performed under fluoroscopic guidance. No data exist on the integration of this catheter within a three-dimensional electroanatomical mapping (3D-EAM) system for left atrial voltage and activation mapping, posterior wall isolation (PWI), or redo ablation. This technical report reviews an approach whereby mapping is performed using the pentaspline PFA catheter itself within an open architectural impedance–based 3D-EAM system. Methods Cases involved mapping with the PFA catheter itself, with real-time visualisation of the guidewire tip and catheter within the 3D-EAM system. In certain cases, additional 3D-EAM was performed with a grid-style high-density mapping catheter for comparison. Results In a series of 22 patients (45% female, mean age 63 ± 13 years, 55% paroxysmal AF, 27% redo procedures), mapping increased procedural times (mean 108 min vs. 68 min in fluoroscopy-only controls), without reducing fluoroscopy times. Three potential advantages of mapping with the PFA catheter were identified: (1) The technique helped identify sleeves of incomplete pulmonary vein isolation after index applications. (2) In the four cases mapped with both the PFA and grid-style catheters, voltage maps appeared concordant. (3) The technique helped facilitate robust PWI and identify inadvertent partial PWI. Conclusions 3D-EAM with a pentaspline PFA catheter itself is feasible, without the need for high-density mapping catheters. This approach has potential advantages over fluoroscopic-only guidance, although its long-term efficacy and cost-effectiveness require formal assessment. Graphical Abstract

Background The aim of this study was to evaluate the impact of contact force (CF) visualization on the incidence of low and high CF during left atrial (LA) mapping and pulmonary vein isolation (PVI). Methods CF was assessed in 70 patients who underwent PVI. Three highly experienced operators performed all procedures. The operators were blinded to CF in group A (35 patients), and CF was displayed in group B (35 patients). In group B, optimal CF was defined as mean CF between 10 and 39 g , and operators attempted to acquire points and ablate within this range. Results A total of 8401 mapping points were analyzed during LA mapping (group A: 4104, group B: 4297). Low CF <10 g and high CF ≥40 g were noted in a significantly larger number of points in group A (37.7 vs. 12.0 %, P  < 0.001; 11.5 vs. 1.5 %, P  < 0.001). At the mitral isthmus and ridge areas, CF was significantly lower (7.7 vs. 12.2 g , P  < 0.001; 5.3 vs. 11.7 g , P  < 0.001) in group A than in group B. PVI was successfully achieved in all patients. There were significant site-dependent CF differences between the two groups. Optimal CF was achieved in significantly more applications in group B ( P  < 0.001). There was no significant difference in atrial fibrillation (AF) recurrence rates after a minimum follow-up of 1 year between the two groups in this cohort ( P  = 0.24). No significant peri-procedural complications occurred in either group. Conclusions CF visualization can assist in avoiding both low and high CF, which may have the potential to improve lesion formation and patient safety profile. In this study, CF-guided ablation did not affect AF recurrence.

Few binding events are here shown to elicit an extended work function change in a large‐area Au‐surface biofunctionalized with ≈108 capturing antibodies. This is demonstrated by Kelvin probe force microscopy (KPFM), imaging a ≈105 µm2 wide Au‐electrodes covered by a dense layer (≈104 µm−2) of physisorbed anti‐immunoglobulin‐M (anti‐IgM). A 10 min incubation in 100 µL phosphate buffer saline solution encompassing ≈10 IgM antigens (10−19 mole L−1  102 × 10−21 m) produces a work function shift ΔW ≈ –60 meV. KPFM images prove that this shift involves the whole inspected area. Notably, no work function change occurs upon incubation in highly concentrated (3 × 10−15 m) nonbinding IgG solutions. The ΔW measured by KPFM is in quantitative agreement with the threshold voltage shift of an electrolyte‐gated single‐molecule large‐area transistor (SiMoT). The findings provide direct experimental evidence for the SiMoT ultrahigh sensitivity, by imaging the extensive shift of the gate work function, likely arising from collective surface phenomena, elicited by single‐molecule binding events. A few antigen–antibody bindings generate an extended work function shift, assessed by Kelvin probe atomic force microscopy (AFM), in a large‐area biofunctionalized Au‐surface covered by 108 antibodies. This striking result compares with the threshold voltage shift measured by electrolyte‐gated single‐molecule transistor sensors and demonstrates that an amplification mechanism of the electrostatic change triggered by a few affinity binding events works even on a barely physisorbed biolayer.

Background Invasive management of atrial tachycardias(ATs) requires proper diagnosis of the mechanism followed by elimination of the responsible substrate. A novel lattice-tip catheter with both high-density mapping and dual ablation properties(radiofrequency-RF/pulsed field ablation-PFA) has been recently introduced for catheter ablation of atrial fibrillation. We present the first study to assess its performance in the management of ATs (diagnostic and therapeutic). Methods Patients with documented ATs were selected. Activation mapping was used for the establishment of the AT mechanism. Confirmation with entrainment was performed, whenever appropriate. Accuracy of the activation mapping in diagnosis, acute ablation efficacy, and procedural characteristics were the study endpoints. Results Twenty patients were included (12 cavotricuspid isthmus-dependent atrial flutters, 5 mitral flutters, 2 roof flutters, and 2 focal ATs). Proper diagnosis was established by activation mapping in all cases. The mean mapping time was 7.85 ± 3.06 min with 296.82 ± 150.9 mean mapping points/minute. The mean ablation time was 54.25 ± 42.97 s. Conversion to sinus rhythm during ablation was achieved in all cases with the exception of a roof flutter that converted to mitral flutter and a case of a parahisian AT in which ablation was not attempted. Patients that received ablation did not experience any arrhythmia recurrence in a mean follow up of 4.14 ± 0.91 months. No major or minor complications occurred. Conclusion The lattice-tip catheter and its dedicated electroanatomical mapping system provided sufficiently detailed activation mapping for the diagnosis of the AT mechanism. The delivered lesions were highly effective acutely, with no adverse events. However, limitations exist and should be acknowledged. Graphical Abstract

Objective The purpose of this study is to explore the left atrium (LA) electrophysiologic abnormalities in atrial fibrillation (AF) patients detected during sinus rhythm and to determine the relationship between the type of AF and the electrophysiologic substrate in the LA. Methods Eighty patients with AF (30 paroxysmal AF, 22 persistent AF, and 28 long-standing AF) and 20 age- and sex-matched patients with left-sided accessory pathway were prospectively studied. High-density three-dimensional electroanatomic mapping was performed during sinus rhythm in LA, which was divided into six segments for regional analysis. Mean bipolar voltage, low voltage zone (LVZ) distribution, LA activation time, and electrogram complexity were assessed. Results The LA mean voltage was 3.67 ± 0.68 mV in no AF group, 2.16 ± 0.63 mV in the paroxysmal, 1.81 ± 0.36 mV in the persistent, and 1.48 ± 0.34 mV in the long-standing AF patients ( P  < 0.001). The total LA activation time was 75.3 ± 5.4 ms in no AF, 89.7 ± 12.3 ms in paroxysmal AF, 104.9 ± 6.1 ms in persistent AF, and 115.6 ± 12.1 ms in the long-standing AF patients, respectively ( P  < 0.001). With the progression of AF, there was a higher incidence of LVZ detection and increased prevalence of complex electrograms with 95 % of complex electrograms in areas with the bipolar voltage ≤ 1.3 mV in persistent and long-standing AF patients. Conclusion Patients with AF have abnormal electrophysiologic substrate in sinus rhythm characterized by lower mean bipolar voltage, more prevalent complex electrograms, and longer LA activation time. This substrate progresses parallel to progression of AF type.

Purpose In this study, we aimed to report our preliminary experience regarding the impact of the novel short-tip (ST) cryoballoon (CB) on procedural efficacy and signal quality during pulmonary vein (PV) isolation for both paroxysmal and persistent atrial fibrillation. Methods Between March, 2015, and August, 2015, we enrolled a total of 64 patients (47 patients male, 73 %) with a mean age of 60 ± 11 years. In the study population, 31 patients (48 %) underwent PVI using Advance (ADV) CB and 33 (52 %) patients with ST CB. In all patients, a 28-mm balloon was used. Results Acute procedural success rates were 100 % for the entire study population. A statistically insignificant increase in the percentage of PV signal recordings was observed with ST CB in all PVs compared to ADV CB [88 vs. 81 % for left superior PV (LSPV), 82 vs. 78 % for left inferior PV (LIPV), 85 vs. 84 % for right superior PV (RSPV), 82 vs. 71 % for right inferior PV (RIPV), p  < 0.05]. Additionally, the difference in minimum temperature reached during the procedure per PV was not statistically significant between ST CB and ADV CB except the LIPV (LSPV −44.2 ± 5.9 vs. −45.6 ± 5.3 °C, p  = 0.970; LIPV −38.7 ± 4.6 °C vs −44.6 ± 6.8 °C, p < 0.001; RSPV −45.6 ± 7.4 °C vs.−47.2 ± 6.1 °C, p = 0.168; RIPV −41.4 ± 5.1 °C vs.−43.7 ± 6.3 °C, p  = 0.360). Time to isolation for each PV was similar between ST and ADV CB ( p  > 0.05). Conclusion Our preliminary findings indicated similar acute procedural success for the novel ST CB compared with second generation ADV CB. The increase in the ratio of PV signal recordings obtained during the PVI using the novel ST CB was not significant.