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Ventricular tachycardia (VT) can originate from diseased myocardium resulting from ischemic or nonischemic cardiomyopathy. Scar-related VT is predominantly sustained by reentrant circuits within areas of myocardial scar. The therapeutic target within these circuits is the isthmus-an electrically insulated pathway bounded by electrical barriers. To elucidate the mechanisms of isthmus formation and the structural characteristics of VT circuits, electrophysiological mapping during VT has advanced in parallel with technological innovations, including intraoperative mapping, electroanatomical mapping, and, more recently, high-density mapping using multipolar catheters. We have recently characterized VT circuits involving the intramural component and proposed a hyperboloid model to conceptualize three-dimensional VT propagation. Furthermore, we demonstrated that the majority of isthmus boundaries are formed by anatomically fixed lines of conduction block, as identified by substrate mapping. Novel technologies, such as a frequency analysis of intracardiac electrograms and micro-mapping catheters for the coronary vessels, have also been developed to investigate intramural VT circuits.

Manganese (Mn) is a major element in various aqueous and soil environments that is sometimes highly concentrated in mine water and other mineral processing wastewater. In this study, we investigated Mn removal from alkaline mine water (pH > 9) with an Mn-coated silica sand packed into a pilot-scale column reactor and examined the specific reaction mechanism using X-ray absorption near-edge structure (XANES) analysis and geochemical kinetic modeling. The kinetic effect of dissolved Mn(II) removal by birnessite (δ-Mn(IV)O2) at pH 6 and 8 was evaluated at different Mn(II)/Mn(IV) molar ratios of 0.1–10. Our results confirmed the positive effect of the presence of δ-MnO2 on the short-term removal (60 min) of dissolved Mn. XANES analysis results revealed that δ-MnO2 was more abundant than Mn(III)OOH in the reactor, which may have accumulated during a long-term reaction (4 months) after the reactor was turned on. A gradual decrease in dissolved Mn(II) concentration with depth was observed in the reactor, and comparison with the kinetic modeling result confirmed that δ-MnO2 interaction was the dominant Mn removal mechanism. Our results show that δ-MnO2 contents could play a significant role in controlling Mn removability from mine water in the reactor.

Heart failure with a reduced ejection fraction (HFrEF) is a common and serious condition often associated with atrial fibrillation (AF) and ventricular arrhythmias, leading to poor outcomes such as rehospitalizations and death. Detecting asymptomatic arrhythmias remains challenging, as traditional monitoring methods like 12-lead electrocardiograms (ECGs) or Holter ECGs are insufficient for continuous surveillance. This study aims to evaluate the utility of continuous arrhythmia monitoring using an implantable loop recorder (ILR) to detect asymptomatic arrhythmias in HFrEF patients, particularly for AF and ventricular tachycardia (VT). This is a single-center, non-randomized exploratory study. Thirty-five patients with HFrEF (LVEF ≤ 40%) and no history of AF will receive ILR implants. Primary endpoints include the detection of new-onset AF lasting at least 6 minutes and sustained or non-sustained VT. Secondary endpoints include the identification of bradycardia, pauses, and other arrhythmias, along with cardiovascular outcomes such as death and hospitalization. Additionally, secondary endpoints will include arrhythmia treatments, including anticoagulation therapy, catheter ablation, and implant of therapy devices. Data will be collected via remote monitoring through the Medtronic CareLink system, with event rates estimated using Kaplan-Meier methods. Data collection will span three years, with analyses conducted in the first and third years. The LINQ2-HF trial is designed to detect new-onset AF and VT in HFrEF patients using ILR, with the aim of informing future strategies for arrhythmia management in this population. Japan Registry of Clinical Trials (jRCT). jRCTs032240593. https://jrct.niph.go.jp/en-latest-detail/jRCTs032240593.

PurposeRapid ventricular pacing (RVP) was reported to improve the cooling effects of the cryoballoon (CB). The aim of this study was to investigate the safety and efficacy of RVP for left atrial posterior wall isolation (PWI) by the CB.MethodsOne hundred consecutive patients (males 80, mean age 63 ± 10 years) with persistent atrial fibrillation underwent left atrial roof (LA-RB) and bottom block line (LA-BB) creation by CB to achieve PWI. Patients were randomized into two groups according to whether they underwent PWI with (RVP group, n = 50) or without RVP (control group, n = 50).ResultsThe nadir CB temperature (NCT) during the LA-RB and LA-BB creation was significantly lower in the RVP group than control group (LA-RB − 45.7 °C and − 43.9 °C, p < 0.001, and LA-BB − 42.4 °C and − 40.0 °C, p < 0.001). The success rate of the LA-RB creation was significantly higher in the RVP group than the control group (98% vs. 88%, p = 0.039), however, there were no significant differences regarding the LA-BB creation (66% vs. 52%, p = 0.15) and PWI (66% vs. 50%, p = 0.1) between the two groups. The PWI success rate did not differ whether CB freezing was prematurely terminated due to an excessive luminal esophageal temperature (LET) drop in the RVP group (65.8% vs. 66.7%, respectively, p = 0.96).ConclusionsRVP significantly decreased the NCT during the CB application resulting in the significant improvement of success rate of the LA-RB. The advantage of RVP in terms of the accomplishing PWI was not affected even when the CB freezing was prematurely terminated due to an excessive LET drop.

Background The innovative peak frequency mapping facilitates the quantification of electrogram sharpness. However, reference values for normal atrial tissue are currently undefined. In this study, we explored the distribution of peak frequency and omnipolar peak-to-peak voltage (V-max) in a normal heart. Methods Twenty-two patients with structurally normal heart were included. Either the right atrium (RA) and superior vena cava (SVC) or the left atrium (LA) and pulmonary veins (PVs) were mapped during sinus rhythm. Results In total, 13,654 points in the RA and 4143 points in the SVC from 15 patients and 4662 points in the LA and 2761 points in PVs from 7 patients were analyzed. The correlation between peak frequency and V-max was weak ( R  = 0.223). The median peak frequency was larger in the SVC than in the RA (441 [358–524] Hz vs. 358 [291–441] Hz, P  < 0.0001) and in PVs than in the LA (346 [253–441] Hz vs. 323 [262–397] Hz, P  < 0.0001). Conversely, the median V-max was smaller in the SVC than in the RA (1.96 [0.77–3.75] mV vs. 4.11 [2.10–6.83] mV, P  < 0.0001) and in PVs than in the LA (1.16 [0.33–3.17] mV vs. 4.42 [2.63–6.84] mV, P  < 0.0001). More than 95% of peak frequencies were > 174 Hz in the RA and > 185 Hz in the LA, and > 95% of V-maxes were > 0.52 and > 1.07 mV in the RA and LA, respectively. Conclusion Given the limited correlation between peak frequency and V-max, and recognizing their potential to provide distinct information, they can be used complementarily. Employing these parameters to extract varied insights can provide comprehensive understandings of tissue characteristics. Graphical abstract

Filamin C (FLNC), recently identified as a causative gene of cardiomyopathy, is widely expressed in cardiomyocytes and is involved in signal transduction between the sarcomere and the plasma membrane. In general, the FLNC truncating variant causes severe dilated cardiomyopathy. A 70-year-old female was referred to our hospital with advanced conduction defects and underwent pacemaker implantation. Cardiac MRI revealed mild hypertrophic cardiomyopathy. As her father also underwent pacemaker implantation due to a cardiac conduction defect, the presence of familial cardiac arrhythmia was suspected. A whole-exome sequencing identified the FLNC truncating variant (NM_001458.5 FLNC:c.592_593del, p.Cys198Argfs*40). We experienced an FLNC-related cardiomyopathy case with predominantly advanced conduction defects, which postulated that the variant mainly affected the conduction system.

Purpose Radiofrequency (RF) ablation with half-normal saline (HNS) irrigation is reported to potentially enlarge local lesion compared to normal saline (NS) in power-controlled ablation (PC-Abl). However, the effect of HNS-irrigation in temperature-flow-controlled ablation (TFC-Abl) on lesion characteristics is unknown. We compared this between TFC-Abl with QDOT-Micro™ catheter and PC-Abl with Thermocool SmartTouch SF™ catheter (STSF). Methods RF-application with NS ( n  = 480) and HNS ( n  = 480) irrigation were performed on swine myocardium placed in a circulating saline bath. Lesion characteristics without steam-pops under various conditions (target AI, 400/550; ablation power, 30/50 W; contact force, 10/20/30 g; catheter orientation, perpendicular/parallel) were assessed and compared between two irrigants. Results After matching, 343 lesions without steam-pops in each group were evaluated. In PC-Abl, lesion size did not differ between two groups (NS, 188 ± 97 vs. HNS, 200 ± 95 mm 3 , p  = 0.28 in volume; 33.9 ± 7.3 vs. 34.8 ± 9.5 mm 2 , p  = 0.34 in surface area; and 4.0 ± 1.0 vs. 4.0 ± 1.0 mm, p  = 0.81 in depth), but steam-pops were more frequently observed with HNS-irrigation (23.8% vs. 37.9%, p  = 0.001). Contrary, in TFC-Abl, HNS-irrigation produced significantly larger (214 ± 106 vs. 243 ± 128 mm 3 , p  = 0.017) and deeper (4.0 ± 1.0 vs. 4.3 ± 1.1 mm, p  = 0.002) lesions without increasing the risk of steam-pops (15.0% vs 15.0%, p  = 0.99). Automatic temperature-guided titration was more frequently observed in HNS-irrigation (54.8% vs. 78.5%, p  < 0.001). Conclusions TFC-Abl with QDOT-Micro™ catheter utilizing HNS-irrigation might increase volume and depth of local lesion without increasing the risk of stem-pops compared to NS-irrigation. Graphical abstract Power-controlled ablation with HNS-irrigation showed similar focal lesion with higher incidence of steam-pops (SPs) compared to normal saline (NS) irrigation. Contrary, temperature-flow-controlled ablation with HNS-irrigation provided larger and deeper lesion than NS-irrigation with similar incidence of SPs. ns, p  > 0.05; *, 0.01 <  p  ≤ 0.05; **, 0.005 <  p  ≤ 0.01. HNS, half-normal saline; NS, normal saline.

Background Lesion size is reported to become larger as contact force (CF) increases. However, this has not been systematically evaluated in temperature‐guided very high‐power short‐duration (vHPSD) ablation, which was therefore the purpose of this study. Methods Radiofrequency applications (90 W/4 s, temperature‐control mode) were performed in excised porcine myocardium with four different CFs of 5, 15, 25, and 35 g using QDOT‐MICRO™ catheter. Ten lesions for each combination of settings were created, and lesion metrics and steam‐pops were compared. Results A total of 320 lesions were analyzed. Lesion depth, surface area, and volume were smallest for CF of 5 g than for 15, 25, and 35 g (depth: 2.7 mm vs. 2.9 mm, 3.0 mm, 3.15 mm, p < .01; surface area: 38.4 mm2 vs. 41.8 mm2, 43.3 mm2, 41.5 mm2, p < .05; volume: 98.2 mm3 vs. 133.3 mm3, 129.4 mm3, 126.8 mm3, p < .01 for all pairs of groups compared to CF = 5 g). However, no significant differences were observed between CFs of 15–35 g. Average power was highest for CF of 5 g, followed by 15, 25, and 35 g (83.2 W vs. 82.1 W vs. 77.1 W vs. 66.1 W, p < .01 for all pairs), reflecting the higher incidence of temperature‐guided power titration with greater CFs (5 g:8.8% vs. 15 g:52.5% vs. 25 g:77.5% vs. 35 g:91.2%, p < .01 for all pairs except for 25 g vs. 35 g). The incidence of steam‐pops did not significantly differ between four groups (5 g:3.8% vs. 15 g:10% vs. 25 g:6.2% vs. 35 g:2.5%, not significant for all pairs). Conclusions For vHPSD ablation, lesion size does not become large once the CF reaches 15 g, and the risk of steam‐pops may be mitigated through power titration even in high CFs. This study demonstrates the effect of CF on 90 W/4 s ablation using QDOT‐MICRO catheter. Lesion sizes do not become larger once CF reaches 15 g. Steam‐pops do not increase with CF owing to the effective power titration with temperature limit.

Abstract PurposeThe size of the distal electrode and the method of measuring local impedance (LI) are different between the IntellaNav MiFi-OI™ (MiFi-OI) and IntellaNav STABLE POINT™ (SP) catheters. We investigated the impact of these differences on LI, efficacy, and safety of radiofrequency (RF) applications.MethodsRF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (10 g and 20 g), and durations (10–120 s) were performed in excised porcine hearts (N = 48). LI variation was defined by δLI-drop (= initial LI − post-RF LI) and %LI-drop (= δLI-drop/initial LI) × 100, and the relationship between lesion characteristics and LI variation was compared.Results A total of 576 lesions were examined. Although absolute δLI-drop during RF applications was significantly larger for the SP than MiFi-OI catheter (47[31–65]ohm for SP vs 37[24–51]ohm for MiFi-OI, p < 0.0001), %LI-drop was similar (23.3 [15.5–30.6]% in SP vs 24.9[17.3–32.5]% in MiFi-OI, p = 0.10). Although lesions produced by both catheters were similarly correlated with LI variation, the SP catheter produced generally larger lesions (depth; 5.0 [3.7–6.1]mm vs 4.7 [3.3–6.0]mm, p = 0.06; surface areas, 46.9 [36.8–58.8]mm2 vs 44.7 [34.3–55.5]mm2, p = 0.02; volume, 321 [165–533]mm3 vs 265[141–471]mm3, p = 0.02). Steam pops were similarly observed with both catheters. In both catheters, %LI-drop was superior to δLI-drop in correlation to lesion size (p < 0.0001) and in predicting steam pops (p < 0.01).ConclusionsAlthough no difference in safety profile is observed between MiFi-OI and SP catheters, the SP catheter produces larger lesions. %LI-drop is superior to δLI-drop in correlation to lesion size and in predicting steam pops as well as in normalizing the difference between catheters.

Introduction The safety of hyperbaric oxygen treatment (HBO2) in patients with cardiovascular implanted electronic devices (CIED) remains unclear. Methods We conducted a retrospective analysis of seven CIED patients (median age 79 [73–83] years, five males [71.4%]), including five with pacemakers and two with implantable cardioverter defibrillators (ICD), who underwent HBO2 between June 2013 and April 2023. During the initial session, electrocardiogram monitoring was conducted, and CIED checks were performed before and after the treatment. In addition, the medical records were scrutinized to identify any abnormal CIED operations. Results All seven CIED patients underwent HBO2 within the safety pressure range specified by the CIED manufacturers or general pressure test by the International Organization for Standardization (2.5 [2.5–2.5] atmosphere absolute × 18 [5–20] sessions). When comparing the CIED parameters before and after HBO2, no significant changes were observed in the waveform amplitudes, pacing thresholds, lead impedance of the atrial and ventricular leads, or battery levels. All seven patients, including two with the rate response function activated, exhibited no significant changes in the pacing rate or pacing failure. Two ICD patients did not deactivate the therapy, including the defibrillation; however, they did not experience any arrhythmia or inappropriate ICD therapy during the HBO2. Conclusion CIED patients who underwent HBO2 within the safety pressure range exhibited no significant changes in the parameters immediately after the HBO2 and had no observable abnormal CIED operations during the treatment. The safety of defibrillation by an ICD during HBO2 should be clarified. The patients with CIEDs who underwent HBO2 within the safety pressure range specified by the ICD manufacturers showed no significant changes in the CIED parameters before or immediately after HBO2, and there were no observable abnormalities in the CIED operation during HBO2.