Bipolar Voltage Research Articles

Local epicardial robotic-enhanced hybrid ablation efficacy predictors for persistent atrial fibrillation

BackgroundHybrid ablation can manage persistent atrial fibrillation (PsAF) and long-standing persistent AF (LSPAF). Robotic-enhanced hybrid ablation (RE-HA) offers greater precision and stability. However, biophysical predictors of effective local epicardial radiofrequency ablation (ELRF) during epicardial ablation are unknown. ObjectiveThis study aimed to compare the time course of biophysical predictors of ELRF and no-ELRF during the first stage of RE-HA in patients with PsAF and LSPAF. MethodsWe conducted a dual-center retrospective cohort study involving 92 consecutive patients with PsAF or LSPAF who underwent RE-HA between January 2021 and May 2024. Epicardial electrogram disappearance, defined as a reduction of bipolar voltages to <0.05mV, baseline impedance (BI), and impedance drop (ID), were compared between ELRF and no-ELRF cases. Univariate and multivariate logistic regression models were used to identify predictive variables. Optimal cutoff values were determined using ROC curves. ResultsAmong 2,474 RF applications, significant predictors of ELRF included BI and ID at 1 and 8 s, with optimal cutoff values of <107, 5–17, and 0–7 Ω. The composite predictive model had an area under the receiver operating characteristics of 0.775, with 94% sensitivity, 53% specificity, and 65% accuracy. Our predictive ELRF score ranged 0–4, and Youden’s J test identifying a cutoff value of 3 as optimal. ConclusionBI and progressive ID were strong predictors of local epicardial RE-HA efficacy. The composite model was a reliable tool for early identification of ELRF, potentially reducing RF delivery and enhancing procedural efficiency. Larger prospective studies are needed to validate these findings.

Anatomy of the Dynamics of the Nucleation of Skyrmions in Nanodots via the Voltage‐Controlled Magnetic Anisotropy

AbstractElectric fields can be employed to efficiently manipulate spin textures in low‐dimensional magnetic systems. In this work, the field‐free formation of magnetic skyrmions in ferromagnetic‐based patterned nanodots with perpendicular magnetic anisotropy and Dzyaloshinskii–Moriya interaction via the voltage‐controlled magnetic anisotropy is studied. By micromagnetic simulations it is demonstrated that by reducing the magnetic anisotropy via an electric voltage pulse with adequate intensity and raise and decay times, it is possible to achieve 100% skyrmion nucleation probability through an intermediate magnetic vortex. The nucleation path is investigated in a Graphene/Co/Pt nanodot varying Co thickness, temperature, and applied field. A complete nucleation/annihilation process via bipolar voltage pulses is also possible enabling the realization of a writing/deleting logic device. The results reveal the relevance of following a quasi‐equilibrium magnetization dynamical path and elucidates the relevance of the absolute stability of the magnetic skyrmion state against other possible magnetic configurations.

A single-center trial ofelectrographic flow mapping and concomitant voltage mapping in sinus rhythm and atrial fibrillation (FLOW EVAL-AF).

Electrographic flow (EGF) mapping reconstructs atrial electrical wavefront propagation, potentially revealing sources of atrial fibrillation (AF). Electrographic flow consistency (EGFC) measures the concurrence of wavefront patterns and may provide insights into atrial substrate health. This study aimed to compare EGF patterns during atrial fibrillation (AF) with sinus rhythm (SR) and explore the correlation between EGFC and regional bipolar voltage. In this single-center, prospective study, AF patients underwent mapping of the atria using bipolar voltage and EGF mapping. Mapping was performed during both AF and SR using a 16-electrode grid catheter (bipolar mapping) and a 64-pole basket catheter (EGF mapping). EGFC was computed as the average modulus of individual EGF vectors, reflecting flow pattern consistency. Ten patients were enrolled. EGF identified 11 sources with a mean source activity of 32 ± 9% during AF. Eight out of eleven sources in AF converted to passive "sinks" when mapped in SR. EGFC was significantly lower during AF compared to SR (0.74 ± 0.14 vs 1.0 ± 0.11 AUs, P < 0.01), consistent with EGFC quantifying the more chaotic wavefront propagation during arrhythmia. No spatial correlation between areas of high EGFC during AF and SR was observed. EGFC correlated with bipolar voltage across rhythms and atria (r = 0.647, P < 0.0001). EGF patterns varied by rhythm with AF showing lower EGFC values. EGFC correlated with bipolar voltage across rhythms and atria, suggesting its potential as an atrial myopathy marker akin to high-density voltage mapping and offering insights into atrial substrate health. Trial registration ClinicalTrials.gov Identifier: NCT06260670.

Abstract 4124323: Extensive atrial cardiomyopathy indicated by left atrial low-voltage areas predicts subsequent stroke after atrial fibrillation ablation

Background: Atrial fibrillation (AF) is a leading cause of stroke. However, predictors of stroke after AF ablation have not been well clarified, therefore, evidences of anticoagulation therapy after the procedure have been limited. Although left atrial low-voltage areas (LVAs) reflects atrial cardiomyopathy, which is a potential cause of thromboembolism, there are few reports of an association between LVAs and stroke. The purpose of this study was to investigate the association between atrial cardiomyopathy assessed by LVAs and stroke in patients undergoing AF ablation. Methods: The study design was a single center, retrospective observational study. This study included 1,486 (age, 68 ± 10 years; female, 501 [34%]; persistent AF, 905 [61%]) consecutive patients who underwent initial AF ablation from December 2014 to March 2022. The definition of LVAs were areas with a bipolar voltage of &lt;0.5 mV in the left atrium. The area of LVAs in the whole left atrium was divided into 3 groups, namely &lt;5cm 2 , 5-20 cm 2 and ≥20 cm 2 . Stroke after AF ablation was followed for 60 months. Results: Of 1,486 patients, LVAs were found in 352 (24%) patients, and 25 (1.7%) patients developed stroke (hemorrhagic stroke, 4 [16%] patients; ischemic stroke 21 [84%] patients). Freedom from stroke was significantly lower in patients with LVAs than in those without (&lt;5cm 2 : 98.3%, 5-20 cm 2 : 95.4%, ≥20 cm 2 : 88.8%, p&lt;0.001). Additionally, LVAs ≥20 cm 2 was an independent predictor of the development of stroke after AF ablation (hazard ratio 4.9, 95% confidence interval: 2.0-12; p=0.001, adjusted by estimated glomerular filtration rate and AF recurrence after ablation). Conclusion: In patients with initial AF ablation, freedom from stroke after AF ablation was significantly lower in patients with LVAs ≥20 cm 2 than in patients with LVAs 5-20 cm 2 and in patients with LVAs &lt;5cm 2 . Particularly, LVAs ≥20 cm 2 was an independent predictor of the development of stroke after AF ablation.

Abstract 4141438: Predictors of Left Atrial Low Voltage Areas Were Different among Age Groups in Patients with Atrial Fibrillation Ablation

Background: Catheter ablation is a well-established treatment for atrial fibrillation (AF). Left atrial low-voltage areas (LVAs) is associated with atrial remodeling following the progression of atrial cardiomyopathy, and poor rhythm outcome after catheter ablation. However, the predictors of LVAs presence have not been fully elucidated in different age groups. Purpose: The purpose of this study was to investigate predictors of the prevalence of LVAs in different age groups. Methods: 1,488 (age, 69 ± 10 years; female, 501 [34%]) consecutive patients who underwent initial ablation were included. Age groups were divided into three groups, namely &lt;60 years old (younger age, n=272), 60-75 years old (intermediate age, n=864), ≥75 years old (older age, n=352). The definition of LVAs was areas with a bipolar voltage of &lt;0.5 mV covering ≥5 cm2 of left atrial surface. Multivariate logistic regression analysis was performed to investigate the clinical predictors of LVAs. Results: Of 1,488 patients, LVAs existed in 352 (24%) patients. In the younger age group, C-reactive protein (odds ratio [OR], 4.5; [95% confidence interval {CI}: 1.5-13], p = 0.006) and previous history of heart failure (OR, 5.6; [95% CI: 1.2-26], p = 0.027) were the independent predictors of LVAs. In the intermediate age group, female (OR, 3.8; [95% CI: 2.6-5.7], p &lt; 0.001), persistent AF (OR, 2.6; [95% CI: 1.7-4.1], p &lt; 0.001), lower body mass index (OR, 0.93; [95% CI: 0.88-0.98], p = 0.004), lower hemoglobin (OR, 0.81; [95% CI: 0.72-0.93], p = 0.002), C-reactive protein (OR, 1.4; [95% CI: 1.0 1-2.0], p = 0.047), diabetes mellitus (OR, 1.8; [95% CI: 1.1-2,8], p = 0.01), left atrial diameter (OR, 1.04; [95% CI: 1.01-1.1], p = 0.007) were the independent predictors of LVAs. In the older age group, female (OR, 2.3; [95% CI: 1.4-3.7], p = 0.01), persistent AF (OR, 3.1; [95% CI: 1.8-5.2], p &lt; 0.001) and lower hemoglobin (OR, 0.83; [95% CI: 0.71-0.97], p = 0.017) were the independent predictors of LVAs. Conclusion: In patients with atrial fibrillation ablation, the independent predictors of LVAs were different among age groups.

Effect of electrode size and distance to tissue on unipolar and bipolar voltage electrograms and their implications for a near-field cutoff

Characteristics of electrograms depend on the electrode design and distance to the electric source. Our aim was to assess the impact of electrode design and distance from the myocardial electric source on the unipolar and bipolar electrograms to deduce a far-field cut-off. We retrospectively analyzed left atrial electroanatomical maps of 25 patients acquired using an ablation catheter with a 4.5 mm tip-, mini- and 2 mm ring electrodes. The unipolar and bipolar electrograms were characterized based on peak-to-peak amplitude, signal duration, maximal slope, and relative power of the high frequency spectrum above 50 Hz (HF_rel). The unipolar electrograms of ring electrodes showed an increased amplitude (140%), slope (150%) and HF_rel (16% vs. 11%) compared to the tip- and mini-electrodes. The median amplitude, slope, and HF_rel for the ring electrodes followed a power-law decay with distance with a steep decline up to 4 mm. This near-field cut-off can be identified based on a HF_rel above 10% in unipolar electrograms. In conclusion, we observed a higher unipolar amplitude for small ring-electrodes compared to larger tip-electrodes. The rapid decay of the amplitude, slope, and HF_rel up to a distance of 4 mm is suggestive for near-field cut-off identified based on HF_rel above 50 Hz.Clinical Trial Registration: NCT04095559.

Unipolar Voltage for Better Characterizing Left Atrium Substrates: Comparing the Predictive Efficacy for Recurrence Post Atrial Fibrillation Ablation in a Post Hoc Analysis of STABLE-SR-III Trial.

While bipolar voltage (BV) is acknowledged as an indicator of viable cardiomyocyte activation, unipolar recording has emerged as an alternative technique due to its advantage of providing a wider field of view. This study aims to compare the efficacy of unipolar voltage (UV) versus BV in predicting ablation recurrence in atrial fibrillation patients. In Substrate Ablation in the Left Atrium during Sinus Rhythm Trial III, 375 patients completed the follow-up with preserved mapping data were included in the analysis. For each patient, the mean UV and BV was obtained from the electrograms sampled in left atrium (LA). Totally 301 patients experience the primary endpoint within 23.0 ± 9.2 months. While both low UV and BV had significant associations with long-term recurrence of atrial tachyarrhythmia (ATa), only mean UV was independently associated with the outcome. The model by UV with ablation feature had higher discriminatory power to predict ATa recurrence compared with BV model (area under the curve [AUC]: 0.858 vs. 0.757, p < 0.001). In subgroup analysis, UV reveals more powerful predictive efficacy compared with BV, with the AUC 0.843 versus 0.751 (p < 0.001) in circumferential pulmonary vein isolation (CPVI) alone cohort and 0.882 versus 0.750 (p < 0.001) in CPVI plus cohort, respectively. UV exhibits higher efficacy for predicting long-term ATa recurrence after ablation compared with BV in elderly patients with atrial fibrillation regardless of whether the patient accepts substrate modification. The outcome suggests that unipolar recording may better characterize LA fibrosis by capturing more comprehensive transmural features than bipolar signals. ClinicalTrials.gov; URL: https://www. gov. Unique Identifier: NCT03462628.

Significance of the local largest bipolar voltage for the optimized ablation strategy using very high-power short duration mode.

Very high-power short-duration (vHPSD) ablation creates shallower lesions, potentially reducing efficacy. This study aims to identify factors leading to insufficient lesions during pulmonary vein antral isolation (PVAI) with vHPSD-ablation and to develop an optimized PVAI strategy using this technology. PVAI was performed on 41 atrial fibrillation patients using vHPSD-ablation (90 W/4 s). Lesion parameters were recorded and analyzed to identify predictors of insufficient lesions. An optimized PVAI strategy, based on these predictors, was tested in subsequent 42 patients. In total, 3099 RF-applications, including 103(3.3%) insufficient lesions, were analyzed. First-pass PVAI was achieved in 19/40(47.5%) right PVs and 24/41(58.5%) left PVs. Multivariate analysis identified significant predictors of insufficient lesions: local largest bipolar voltage (Bi-V), average contact force, baseline impedance, impedance drop, temperature rise, inter-lesion distance (ILD), and anatomical location (carina or not). An ILD:4-6 mm increased the risk of insufficient lesions 2.2-fold, and lesions at the carina increased it 3.6-fold for both ILD < 4 mm and ILD:4-6 mm. Local largest Bi-V was the strongest predictor for insufficient lesions. The optimized PVAI approach, utilizing vHPSD-ablation with an ILD < 4 mm in non-carinal areas with Bi-V < 4 mV, and high-power ablation-index guided ablation (HPAI, 50 W, ablation-index:450-550) in remaining areas, achieved first-pass PVAI in 92.7% of right PVs and 88.1% of left PVs, using vHPSD-ablation in approximately 65% of total RF-applications. The optimized PVAI achieved significantly higher first-pass PVI rate (p < .0001) with shorter ablation time (p = .04). Appropriate use of vHPSD and HPAI, based on local largest Bi-V and anatomical information, may achieve high first-pass PVAI rates in shorter ablation time with minimal energy delivery.

Exploring LGE areas in the atria: Insights from electroanatomical voltage mapping in AF patients

Abstract Introduction Late gadolinium enhancement MRI (LGE MRI) is a common method for the evaluation of the atrial substrate in atrial fibrillation (AF) patients. The extent of LGE is associated with atrial cardiomyopathy and ablation outcomes. However, previous studies have yielded inconsistent results in detecting low voltage areas (LVA) using bipolar electroanatomical mapping (EAM) in LGE regions. Objective Conduct a thorough analysis of the bipolar and unipolar voltage in LGE areas and its relationship with the voltage in non-LGE areas, utilizing high-density (HD) EAM generated by a multipolar HD-mapping catheter. Methods In this study, 20 patients undergoing AF ablation were examined using LGE-MRI. A 3D mesh integrating LGE data was generated. HD-EAM (&amp;gt; 4000 points) was performed in sinus rhythm. The EAM map and MRI mesh underwent manual alignment and registration. Using a nearest neighbor algorithm, EAM points nearest to LGE areas were identified, and the corresponding unipolar and bipolar voltage values, along with LGE voxel intensity, were exported for analysis. Results LGE areas exhibited a median bipolar voltage amplitude of 0.93 mV, median unipolar voltage of 1.73 mV. In contrast, areas without enhancement displayed median bipolar voltage of 2.33 mV, unipolar voltage of 3.58 mV. We observed a variation in voltage amplitudes across the different LGE areas: bipolar voltage ranged from 0.04 to 2.51 mV and unipolar voltage from 0.22 to 3.75 mV. This variation strongly correlated with voxel intensity in LGE areas (correlation coefficient r = -0.86 [p &amp;lt;0.001]). Irrespective of the voltage amplitude in the examined LGE areas, a significant voltage drop was observed, with an average reduction of 54% in bipolar and 51% in unipolar voltages, compared to the amplitudes in non-LGE areas within the same atria. Conclusion Variations in bipolar and unipolar voltage within LGE areas are significantly correlated with local voxel intensity. Despite the inconsistent overlap with the predefined bipolar threshold for LVA, LGE regions exhibit a pronounced and consistent reduction in both bipolar and unipolar voltage compared to non-LGE areas. This pattern suggests notable electrophysiological changes in these areas. These insights underscore the need for further investigation to better understand the implications and mechanisms underlying these alterations in LGE regions.

Tricuspid regurgitation in atrial fibrillation: correlation to left atrial myopathy and improvement post ablation

Abstract Background Atrial fibrillation (AF) closely correlates to left atrial (LA) myopathy, which in turn can cause functional mitral regurgitation (FMR). The correlation of LA myopathy to tricuspid regurgitation (TR) is still unknown. Data on the dynamic change of TR post AF ablation is still limited. Purpose We sought to investigate the correlation of LA myopathy to TR and furthermore if TR can be improved by AF ablation. Methods Consecutive patients presenting for first time AF ablation were prospectively enrolled. All patients underwent transthoracic echocardiography at baseline as well as 6 months after the ablation procedure. TR was graded as follows: minimal, mild, moderate and severe (I-IV). All study participants underwent high density bipolar voltagemaps prior to AF ablation to characterize the presence of atrial myopathy. Results Our final study cohort consisted of 143 patients (age 64±11 years, 47% female, 48% persistent AF). 15% had no, 21% minimal, 35% mild, 19% moderate and 9% severe TR, respectively. High density maps with 1325±736 mapping points and with an average bipolar voltage of 1.58±0.89mV were created. A significant decline of average LA bipolar voltage was obvious, when comparing patients without TR to any severity level of TR (p=0.015) (Figure 1), however there was no significant difference in LA bipolar voltage, when comparing different TR severity levels (Figure 1). After a follow up of 6 months a significant improvement of TR was observed (p&amp;lt;0.001) with a median level of improvement by one level. 27% had no, 21% minimal, 31% mild, 18% moderate and 2% severe TR, respectively. Conclusion In patients presenting for AF ablation TR closely correlates with LA myopathy according to decreased levels of LA bipolar voltage. AF ablation results in highly significant TR level improvement.

Unipolar electroanatomical mapping outperforms bipolar voltage in detecting LGE areas in the left atrium

Abstract Introduction In atrial fibrillation (AF) management, understanding left atrial substrate is crucial. While both electroanatomical mapping (EAM) and late gadolinium enhancement MRI (LGE MRI) are reliable methods in assessing atrial substrate and are associated with the ablation outcome, recent findings have highlighted significant discrepancies between bipolar low voltage areas (LVA) in EAM and LGE areas. Objective Explore the relationship between LGE areas and unipolar LVAs by utilizing multipolar high-density (HD) mapping. Methods Nineteen patients scheduled for AF ablation underwent pre-ablation LGE-MRI. Left atrial (LA) segmentation was conducted using a convolutional neural network, which subsequently generated a 3D mesh integrating the LGE data. HD-EAM was performed in sinus rhythm for each patient, capturing at least 4000 points. The EAM map and LGE MRI mesh were co-registered. LVA areas were defined using voltage cut-offs of 0.5 mV for bipolar and 2.5 mV for unipolar measurements. Correspondence between LGE areas and LVAs on the anterior and posterior LA wall was analyzed. Results Both bipolar and unipolar LVA demonstrated high precision in detecting LGE areas (100% and 88% respectively). However, unipolar LVA exhibited a remarkable accuracy of 81% for detecting LGE areas specifically, whereas bipolar LVA displayed a significantly lower accuracy of 28%. These findings were consistent across the different atrial walls. Conclusion Incorporating unipolar voltage data into electroanatomical mapping in the atrium may bridge the observed gap between LGE areas and bipolar LVAs. Our findings highlight the significance of unipolar voltage in evaluating the left atrial substrate, potentially offering a more comprehensive insight into the different layers of atrial walls, and opening the door for new approaches in AF therapy.

Impact of left atrial stiffness measurement as a pre-procedural predictor of an extensive left atrial low-voltage area

Abstract Background The presence of a left atrial (LA) low-voltage area (LVA) after pulmonary vein isolation for atrial fibrillation (AF) is a strong predictor of recurrence and LVAs are often an additional ablation target. However, predicting the presence of an LVA before the procedure remains challenging. Purpose To assess the LA stiffness index as a preprocedural predictor of an extensive LVA. Methods We prospectively evaluated 74 patients who underwent catheter ablation for AF and high-density bipolar LA voltage mapping during sinus rhythm or high right atrial pacing. "LVA" was defined as an area with bipolar electrograms (&amp;lt;0.5 mV), while "extensive LVA" was defined as the presence of an LVA that covered more than 15% of the LA surface. Echocardiographic measurements, including the LA volume index (LAVi), E/e' ratio, LA reservoir strain (LASr), and LA stiffness index, calculated as the ratio of E/eʹ to LASr, were performed prior to catheter ablation in all patients. Results Overall, 17 patients (23.0%) had an extensive LVA. Patients with extensive LVAs were older (73 ± 7 vs. 66 ± 8 years; P=0.003), predominantly female (59% vs. 23%; P=0.01), and more frequently showed persistent AF (59% vs. 30%; P=0.04) in comparison to patients without extensive LVAs. According to a receiver operating characteristic curve analysis, the LA stiffness index was more accurate than the LAVi or LASr for predicting extensive LVAs (Figure), allowing using a cutoff value ≥0.6 with 73% sensitivity and 91% specificity. A multivariate logistic regression analysis revealed that the LA stiffness index was an independent predictor of an extensive LVA (odds ratio [OR], 44.11; 95% CI 3.83–507.47, P=0.002). Conclusion The LA stiffness index was a robust predictor of the extent of LVAs in AF patients and thus could be useful for the preprocedural selection of candidates for catheter ablation and to determine the most effective ablation strategies.

Severity of anemia is correlated with the prevalence of left atrial low-voltage areas in patients with atrial fibrillation ablation

Abstract Background Although left atrial low-voltage areas (LVAs) are well-known indicator of atrial fibrosis and atrial fibrillation (AF) recurrence after catheter ablation, the association between anemia and prevalence of LVAs has not been clarified. We hypothesized that LVAs were more frequently found in patients with anemia than in those with normal hemoglobin levels. Purpose The purpose of this study was to investigate the association between hemoglobin levels and the prevalence of LVAs in patients with AF ablation. Methods In total, 1,473 (age, 68±10 years; female, 492 [33%]; persistent AF, 895 [61%]; CHA2DS2-VASc score, 2.5±1.5 points) consecutive patients who underwent initial AF ablation were enrolled in this study. Hemoglobin levels were measured before the ablation procedure, and anemia was defined as hemoglobin levels &amp;lt; 13.5 g/dL in male and &amp;lt; 12.0 g/dL in female. LVAs was defined as areas with bipolar voltage of &amp;lt;0.5 mV covered ≥5 cm² of left atrial surface area. Results Of 1,473 patients, LVAs existed in 348 (24%) patients. Hemoglobin levels was significantly lower in patients with LVAs than those without (13.4 ± 1.7 vs. 14.2 ± 1.5 g/dL, p &amp;lt;0.001). On classification by gender, only in male, hemoglobin levels were significantly lower in patients with LVAs than those without (Figure 1). The prevalence of LVAs increased with decreasing hemoglobin levels (Figure 2). On multivariate analysis including gender as a variable, anemia was an independent predictor of LVAs (odds ratio, 1.6; 95% confidence interval: 1.1–2.3; p=0.03). Conclusions The prevalence of LVAs increased with decreasing hemoglobin levels in patients with AF ablation. In particular, hemoglobin levels &amp;lt; 13.5 g/dL in male and &amp;lt; 12.0 g/dL in female was an independent predictor of LVA presence.Hemoglobin levels and LVAs presenceHemoglobin and the prevalence of LVAs

Preliminary results of the non-invasive cardiac radioablation for ventricular tachycardia study; an in silico dosimetric comparison of photon vs proton radiotherapy for ventricular arrhythmias

Abstract Background Stereotactic arrhythmia radio-ablation (STAR) has been proposed as an alternative treatment for refractory ventricular arrhythmias (VA) in patients who are unsuitable or refractory to standard catheter ablation (CA). It consists in the application of external beam radiotherapy in a single dose of 25 Gy to the target areas. Most of the STAR treatments performed so far used photon radiotherapy. As compared to photons, particle therapy with protons, based on its finite penetration depth in tissue, might have the potential to reduce the dose to surrounding healthy tissues thus lowering the risk of side effects. Purpose The purpose of this in silico simulation study was to evaluate the feasibility of STAR with protons in patients with VA and to compare the doses of the organs at risk (OARs) in photon and proton treatment plans. Methods 14 patients (11 males) candidates to standard CA for VA were enrolled. ECG gated CT scans in expiratory breath-hold, and standard electroanatomical mapping were performed in each patients to reconstruct a 3D bipolar voltage map and identify the ablation target. Based on the information obtained by the contouring of the ablation target three treatment plans were simulated: one with photons, and two with protons - with and without cardiac gating- to assess the doses at the OARs. Results The median age was 68.5 (63.25-71.5), all patients had a history of recurrent VA and the indication for treatment with CA. 7 patients had an ischemic cardiomyopathy, 4 an idiopathic cardiomyopathy and 3 ventricular ectopic beats without structural heart disease. The mean left ventricular ejection fraction was 40±11% and 8 out of 14 patients were ICD carriers. Both photons and protons treatment plans reached the goals for target coverage (25 Gy on 98% of the target volume). A statistically significant reduction in the mean maximum dose (Dmax) to some OARs was observed in proton compared to photon plans (see table 1). Specifically, the Dmax delivered to the mitral valve, vena cava, descending aorta, esophagus and to the lungs have been largely reduced with the proton plans. However, in some specific cases, a higher maximum dose was observed for protons in structures close or overlapping with the target, mainly due to the need of an additional margin in the treatment plan to account for proton range uncertainty. The use of cardiac gating did not show a significant dose reduction to OARs compared to the non-gated proton plan. Conclusion The preliminary results of our in silico simulation study suggest that STAR therapy with the use of protons might be associated with a significant dose reduction to the surrounding organs. Nevertheless, the choice of the best treatment should be evaluated on a case by-case strategy since some specific cases may be better suitable for photon treatment.Table 1

A Wearable Multichannel Electrical Stimulator for Tremor Suppression

Abstract Pathological wrist and finger tremors can be mitigated by out-of-phase stimulation of the sensory nerves in the flexor and extensor muscles. This study endeavors to develop a portable, multichannel electrical stimulator designed to deliver high-frequency, low-intensity, biphasic charge-balanced current pulses within a practical load range to effectively suppress wrist and finger tremors. The circuit architecture integrates an Arduino Nanomicrocontroller, a four-channel digital potentiometer, and four Howland current pumps. The Howland current pump, employing an operational amplifier, generates bipolar currents by accepting bipolar voltages, whereas the digital potentiometer offers programmable bipolar voltages via its wiper terminals. Experimental results indicate that the pulse frequency can be adjusted between 50 Hz and 200 Hz, and the current level can be modulated within a range of −10 mA to +10 mA, with load resistance spanning 100 Ω to 1.3 kΩ. This portable and multichannel device is effective in delivering high-frequency, low-intensity sensory nerve stimulation through programmable biphasic charge-balanced current pulses. The proposed stimulator has the potential to enable adaptive muscle activation, thereby initiating, promoting, and generating movements, and facilitating interactive in-home neurorehabilitation for disabled patients. The portability and programmability of this device make it a promising tool for personalized tremor management and rehabilitation, enhancing the quality of life for individuals with motor impairments.

Dynamic Voltage Mapping of the Post-infarct Ventricular Tachycardia Substrate: A Practical Technique to Help Differentiate Scar from Borderzone Tissue.

During catheter ablation of post-infarct ventricular tachycardia (VT), substrate mapping is used when VT is non-inducible or poorly tolerated. Substrate mapping aims to identify regions of slowly conducting myocardium (borderzone) within and surrounding myocardial scar for ablation. Historically, these tissue types have been identified using bipolar voltage mapping, with areas of low bipolar voltage (<0.50 mV) defined as scar, and areas with voltages between 0.50 mV and 1.50 mV as borderzone. In the era of high-density mapping, studies have demonstrated slow conduction within areas of bipolar voltage <0.50 mV, suggesting that this historical cut-off is outdated. While electrophysiologists often adapt voltage cut-offs to account for this, the optimal scar-borderzone threshold is not known. In this review, we discuss dynamic voltage mapping, a novel substrate mapping technique we have developed, which superimposes data from both activation and voltage maps, to help delineate the post-infarct VT circuit through identification of the optimal scar-borderzone voltage threshold.

Performance of a Bipolar Output Voltage DC-DC Converter for Voltage Regulation for Solar PV System Application

Performance of a Bipolar Output Voltage DC-DC Converter for Voltage Regulation for Solar PV System Application

Unipolar voltage electroanatomic mapping detects structural atrial remodeling identified by LGE-MRI

BackgroundIn atrial fibrillation (AF) management, understanding left atrial (LA) substrate is crucial. While both electroanatomic mapping (EAM) and late gadolinium enhancement magnetic resonance imaging (LGE-MRI) are accepted methods for assessing the atrial substrate and are associated with ablation outcome, recent findings have highlighted discrepancies between low-voltage areas (LVAs) in EAM and LGE areas. ObjectiveThe purpose of this study was to explore the relationship between LGE regions and unipolar and bipolar LVAs using multipolar high-density mapping. MethodsTwenty patients scheduled for AF ablation underwent preablation LGE-MRI. LA segmentation was conducted using a deep learning approach, which subsequently generated a 3-dimensional mesh integrating the LGE data. High-density EAM was performed in sinus rhythm for each patient. The electroanatomic map and LGE-MRI mesh were coregistered. LVAs were defined using cutoffs of 0.5 mV for bipolar voltage and 2.5 mV for unipolar voltage. The correspondence between LGE areas and LVAs in the LA was analyzed using confusion matrices and performance metrics. ResultsA considerable 87.3% of LGE regions overlapped with unipolar LVAs, compared with only 16.2% overlap observed with bipolar LVAs. Across all performance metrics, unipolar LVAs outperformed bipolar LVAs in identifying LGE areas (precision: 78.6% vs 61.1%; sensitivity: 87.3% vs 16.2%; F1 score: 81.3% vs 26.0%; accuracy: 74.0% vs 35.3%). ConclusionOur findings demonstrate that unipolar LVAs strongly correlate with LGE regions. These findings support the integration of unipolar mapping alongside bipolar mapping into clinical practice. This would offer a nuanced approach to diagnose and manage AF by revealing critical insights into the complex architecture of the atrial substrate.

Heart Failure with Preserved Ejection Fraction Correlates with Fibrotic Atrial Myopathy in Patients Undergoing Atrial Fibrillation Ablation.

Background: The incidence of atrial fibrillation (AF) in patients with heart failure with preserved ejection fraction (HFpEF) is high. Impaired left atrial (LA) function is a major determinant in HFpEF. However, the extent of electrical LA tissue degeneration in HFpEF is unknown. Therefore, we sought to investigate the amount of arrhythmogenic and fibrotic LA tissue degeneration in HFpEF patients presenting for AF ablation. Methods: We prospectively screened consecutive patients presenting for first time AF ablation. The HFA-PEFF score was used to identify HFpEF patients. Bipolar high-density voltage mapping was created in sinus rhythm prior to ablation to evaluate the general LA bipolar voltage and quantify areas of low voltage. LVAs were defined as areas with bipolar voltage < 0.5 mV. Results: In total, 187 patients were prospectively enrolled (age 65 ± 11 years, 45% female, 46% persistent AF, 25% HFpEF) in this study. HFpEF patients were older and had a higher CHA2DS2-VASc score (70 ± 9 vs. 63 ± 11 years and 3.2 ± 1.5 vs. 2.3 ± 1.5, each p < 0.001, respectively). Overall, low-voltage areas (LVAs) were present in 97 patients (52%), whereas 76% of the HFpEF population had LVA, as compared to 44% of patients without HFpEF (p < 0.001). HFpEF was associated with generally decreased LA bipolar voltage (1.09 ± 0.64 vs. 1.83 ± 0.91 mV; p < 0.001) and predictive of the presence of low-voltage areas (76% vs. 44% p < 0.001). The HFA-PEFF score inversely correlated with LA bipolar voltage (=-0.454; p < 0.001). Conclusions: HFpEF closely relates to generally decreased LA bipolar voltage and to the existence of fibrotic and arrhythmogenic LA tissue degeneration.

The effect of fixed and functional remodelling on conduction velocity, wavefront propagation, and rotational activity formation in atrial fibrillation.

Pathophysiology of atrial fibrillation (AF) remains unclear. Interactions between scar and conduction velocity (CV) and their impact on wavefront propagation in sinus rhythm (SR) and rotational activity burden in AF were evaluated. Local activation times (LATs) and voltage data were obtained from patients undergoing ablation for persistent AF. Omnipolar voltage (OV) and bipolar voltage (BV) data were obtained during AF and SR at pacing intervals of 600 and 250 ms. Local activation times were used to determine CV dynamics and their relationship to the underlying voltage and pivot points in SR. Computational modelling studies were performed to evaluate the impact of CVs and fibrosis on rotational activity burden in AF. Data from 60 patients with a total of 2 768 400 LAT and voltage points were analysed (46 140 ± 5689 points/patient). Voltage determined CV dynamics. Enhanced CV heterogeneity sites were predominantly mapped to low-voltage zones (LVZs) (0.2-0.49 mV) (128/168, 76.2%) rather than LVZs (<0.2 mV) and frequently co-located to pivot points (151/168, 89.9%). Atrial fibrillation OV maps correlated better with SR BV 250 ms than 600 ms maps, thereby representing fixed and functional remodelling. Sinus rhythm maps at 250 ms compared with 600 ms harboured a greater number of pivot points. Increased CV slowing and functional remodelling on computational models resulted in a greater rotational activity burden. Conduction velocity dynamics are impacted by the degree of scar. Conduction velocity heterogeneity and functional remodelling impacts wavefront propagation in SR and rotational activity burden in AF. This study provides insight into the pathophysiology of AF and identifies potential novel ablation targets.