Termination Sites Research Articles

Nuclear-localized pyruvate kinases control phosphorylation of histone H3 on threonine 11.

Phosphorylation of histone H3 at threonine 11 (H3T11ph) affects transcription and chromosome stability. However, the enzymes responsible for depositing H3T11ph and the functions of H3T11ph in plants remain unknown. Here we report that in Arabidopsis thaliana, PYRUVATE KINASE 6 (PK6), PK7 and PK8 enter the nucleus under conditions of sufficient glucose and light exposure, where they interact with SWI2/SNF2-RELATED 1 COMPLEX 4 (SWC4) and phosphorylate H3 at threonine 11. Mutations in these kinases or knockdown of SWC4 resulted in FLC-dependent early flowering, short hypocotyls and short pedicels. Genome-wide, H3T11ph is highly enriched at transcription start sites and transcription termination sites, and positively correlated with gene transcript levels. PK6 and SWC4 targeted FLC, MYB73, PRE1, TCP4 and TCP10, depositing H3T11ph at these loci and promoting their transcription, and PK6 occupancy at these loci requires SWC4. Together, our results reveal that nuclear-localized PK6, PK7 and PK8 modulate H3T11ph and plant growth.

Chalcogen and halogen surface termination coverage in MXenes—structure, stability, and properties

MXenes are a diverse family of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides. They can be synthesized through both top-down approaches, such as selective etching of A-layers from MAX phases using acids or molten salts, and bottom-up approaches, such as direct synthesis using chemical vapor deposition. However, the degree of the surface termination coverage depends on the synthesis route and is one key parameter for controlling its properties. This study focuses on halogen- and chalcogen-terminated MXenes, particularly M2CTx where M = Ti, Zr, V, Nb, Ta, and T = S, Se, Te, Cl, Br, I, and with surface termination coverage ranging from 100% (ideal, x = 2) to 50% (x = 1). The incorporation of oxygen on vacant termination sites was also evaluated. Using density functional theory (DFT) calculations, we investigated the structural, electronic, and mechanical properties of these MXenes. Our findings reveal that non-ideal termination coverage (x < 2) is more favorable for MXenes terminated with a larger size of T, such as Ti2CBrx, Nb2CClx, and Ta2CClx, and leads to mixed termination sites and lower binding energies. A reduced binding energy may facilitate delamination into single sheets, however, too low termination coverage may also cause structural collapse. Electronic properties showed an increased number of states at the Fermi level under non-ideal coverage, potentially enhancing the conductivity. Mechanically, we find the moduli of MXenes to be comparable to other 2D materials, such as transition metal chalcogenides and hexagonal boron nitride, indicating their suitability for applications requiring flexibility and durability. This study underscores the potential of tailoring MXene properties through precise control of termination coverage and composition, paving the way for enhanced application-specific performance.

Inhibition Clathrin Mediated Endocytosis: Pitstop 1 and Pitstop 2 Chimeras.

Twenty-five chimera compounds of Pitstop 1 and 2 were synthesised and screened for their ability to block the clathrin terminal domain-amphiphysin protein-protein interaction (NTD-PPI using an ELISA) and clathrin mediated endocytosis (CME) in cells. Library 1 was based on Pitstop 2, but no notable clathrin PPI or in-cell activity was observed. With the Pitstop 1, 16 analogues were produced with 1,8-naphthalic imide core as a foundation. Analogues with methylene spaced linkers and simple amides showed a modest to good range of PPI inhibition (7.6-42.5 μM, naphthyl 39 and 4-nitrophenyl 40 respectively) activity. These data reveal the importance of the naphthalene sulfonate moiety, with no des-SO3 analogue displaying PPI inhibition. This was consistent with the observed analogue docked poses within the clathrin terminal domain Site 1 binding pocket. Further modifications targeted the naphthalene imide moiety, with the installation of 5-Br (45 a), 5-OH (45 c) and 5-propyl ether (45 d) moieties. Among them, the OH 45 c and propyl ether 45 d retained PPI inhibition, with propyl ether 45 d being the most active with a PPI inhibition IC50=7.3 μM. This is 2x more potent than Pitstop 2 and 3x more potent than Pitstop 1.

Spontaneous termination of ventricular tachycardia in the human heart.

Understanding the spatiotemporal location of the spontaneous termination of ventricular tachycardia (VT) may provide new insights for ablation. To test the hypothesis that spontaneous VT termination most frequently occurs at the VT exit due to source-sink mismatch and to characterize electrophysiological properties of the sites termination during VT and with extra-stimulus technique. Retrospective analysis of intraoperative mapping studies of nine patients with ischemic cardiopathy or repaired tetralogy of Fallot. Simultaneous endocardial and epicardial mapping was performed in both ventricles using a custom mapping array during VT. Electrogram (EGM) characteristics before and at the moment of termination were analyzed including: cycle length oscillations, EGM heterogeneity and a variation in the systolic/diastolic path. The decrements to extra stimulus were analysed for termination sites and other diastolic sites. Nine VTs in seven patients demonstrated spontaneous VT termination. Seven VTs (77.8%) spontaneously terminated in the final third of the systolic interval, one (11.1%) in early diastole and one (11.1%) in mid diastole. Cycle length oscillations (prolongation, shortening, and no change) were seen in equal frequency. Four VTs (44.4%) showed alternans in the local EGM at the site of termination and this was more prevalent than alternans at other sites in the diastolic pathway (p < .001). Only one-third of VTs showed a change in activation pattern before termination. There was no difference based on etiology. During substrate characterization with extra-stimulus pacing, sites of spontaneous termination showed greater decrement than other sites of the VT circuit during pacing (43.5 ± 14.5 ms vs. 31.2 ± 31.2 ms; p = .003). The entrance zone rather than the exit is the commonest site for the spontaneous termination of VT in the human heart. These sites tend to demonstrate EGM alternans during VT and greater decrement during extrastimulus pacing. These findings may help guide future studies into improving the success of VT ablation.

Full-Length Transcriptome Profiling of the Complete Mitochondrial Genome of Sericothrips houjii (Thysanoptera: Thripidae: Sericothripinae) Featuring Extensive Gene Rearrangement and Duplicated Control Regions.

The mitochondrial genome (mitogenome) of Thysanoptera has extensive gene rearrangement, and some species have repeatable control regions. To investigate the characteristics of the gene expression, transcription and post-transcriptional processes in such extensively gene-rearranged mitogenomes, we sequenced the mitogenome and mitochondrial transcriptome of Sericothrips houjii to analyze. The mitogenome was 14,965 bp in length and included two CRs contains 140 bp repeats between COIII-trnN (CR1) and trnT-trnP (CR2). Unlike the putative ancestral arrangement of insects, S. houjii exhibited only six conserved gene blocks encompassing 14 genes (trnL2-COII, trnD-trnK, ND2-trnW, ATP8-ATP6, ND5-trnH-ND4-ND4L and trnV-lrRNA). A quantitative transcription map showed the gene with the highest relative expression in the mitogenome was ND4-ND4L. Based on analyses of polycistronic transcripts, non-coding RNAs (ncRNAs) and antisense transcripts, we proposed a transcriptional model of this mitogenome. Both CRs contained the transcription initiation sites (TISs) and transcription termination sites (TTSs) of both strands, and an additional TIS for the majority strand (J-strand) was found within antisense lrRNA. The post-transcriptional cleavage processes followed the "tRNA punctuation" model. After the cleavage of transfer RNAs (tRNAs), COI and ND3 matured as bicistronic mRNA COI/ND3 due to the translocation of intervening tRNAs, and the 3' untranslated region (UTR) remained in the mRNAs for COII, COIII, CYTB and ND5. Additionally, isoform RNAs of ND2, srRNA and lrRNA were identified. In summary, the relative mitochondrial gene expression levels, transcriptional model and post-transcriptional cleavage process of S. houjii are notably different from those insects with typical mitochondrial gene arrangements. In addition, the phylogenetic tree of Thripidae including S. houjii was reconstructed. Our study provides insights into the phylogenetic status of Sericothripinae and the transcriptional and post-transcriptional regulation processes of extensively gene-rearranged insect mitogenomes.

Lessons from ablation responses to preferential wavefront in typical atrial flutter.

The heterogeneous conduction properties through the cavotricuspid isthmus (CTI) in typical atrial flutter (AFL) have not yet been well elucidated. We sought to investigate preferential conduction through the CTI and the efficacy of ablation targeting preferential wavefront (PW) guided by ultra-high-resolution mapping. In retrospective study, 28 patients were enrolled. Wavefront propagation patterns through the CTI and ablation responses at the location of PW were evaluated. In the following prospective study, 23 patients with predominant PW across the CTI were enrolled and assigned to the arm of PW prior ablation and the arm of conventional ablation. Five activation patterns were noticed in the retrospective study. The termination sites were exactly located at the PW in 18 of 28 patients (64.3%). The width of the PW in direct termination group was significantly narrower than that in the CL prolongation before termination group (16.6 ± 1.0mm vs. 23.3 ± 3.4mm, respectively, p = 0.025). In the prospective study, the voltage of PW region was significantly higher than non-PW regions both from unipolar and bipolar mapping. 21 of 23 patients (91.3%) were terminated at PW. AFL could no longer be induced immediately after termination. The time from radiofrequency application to AFL termination and to achieve bidirectional conduction block was significantly shorter in PW prior ablation arm than that in conventional ablation group (p < 0.05). Ablation targeting the PW first could be more efficient to terminate typical AFL and to achieve the endpoint of bidirectional conduction block.

Morphological and Histological Description of Spiny Dogfishshark Liver, Squalusacanthais(Linnaeus,1758),Elasmobranchii,Squaliformes

The current study describes the morphological and histological appearance of the liver of the spiny dogfish Squalusacanthais, which is classified as Class: Chondrichthyes, Subclass: Elasmobranchi. Morphologically, the liver was observed as large, and consists of two symmetrical lobes connected from the upper side, and the gallbladder was observed in the right lobe. Histologically, liver sections were prepared with H&amp;E stain, and examined with a light microscope. Hepatic parenchyma was surrounded by a capsule of connective tissue and primarily composed of hepatocytes. The nuclei of these cells were observed at the terminal site, with lipid droplets in the cytoplasm. Central veins were observed, surrounded by connective tissue and lined with a squamous epithelial layer. Hepatocytes were, separated by numerous blood sinusoids with connective tissue. Blood arteries were observed, surrounded by thick muscular fiber walls and narrow lumens compared to veins. The portal vein was observed, along with the artery and bile duct, surrounded by a thick connective tissue. The bile duct was surrounded by a layer of muscular fibers, lined with a simple columnar epithelial layer with clear nuclei, and a connective tissue layer. Melanin-containing cells were observed, but no hepatic lobules or connective tissue were seen between them. Additionally, Hepato-pancreatic tissue was not identified.

Optimizing the production of dsRNA biocontrols in microbial systems using multiple transcriptional terminators.

Crop pests and pathogens annually cause over $220 billion in global crop damage, with insects consuming 5%-20%of major grain crops. Current crop pest and disease control strategies rely on insecticidal and fungicidal sprays, plant genetic resistance, transgenes, and agricultural practices. Double-stranded RNA(dsRNA) is emerging as a novel sustainable method of plant protection as an alternative to traditional chemical pesticides. Successful commercialization of dsRNA-based biocontrols requires the economical production of large quantities of dsRNA combined with suitable delivery methods to ensure RNAi efficacy against the target pest. In this study, we have optimized the design of plasmid DNA constructs to produce dsRNA biocontrols in Escherichia coli, by employing a wide range of alternative synthetic transcriptional terminators before measurement of dsRNA yield. We demonstrate that a 7.8-fold increase of dsRNA was achieved using triple synthetic transcriptional terminators within a dual T7 dsRNA production system compared to the absence of transcriptional terminators. Moreover, our data demonstratethat batch fermentation production dsRNA using multiple transcriptional terminators is scalable and generates significantly higher yields of dsRNA generated in the absence of transcriptional terminators at both small-scale batch culture and large-scale fermentation. In addition, we show that application of these dsRNA biocontrols expressed in E. coli cells results in increased insect mortality. Finally, novel mass spectrometry analysis was performed to determine the precise sites of transcriptional termination at the different transcriptional terminators providing important further mechanistic insight.

Analysis of RNA translation with a deep learning architecture provides new insight into translation control.

Accurate annotation of coding regions in RNAs is essential for understanding gene translation. We developed a deep neural network to directly predict and analyze translation initiation and termination sites from RNA sequences. Trained with human transcripts, our model learned hidden rules of translation control and achieved a near perfect prediction of canonical translation sites across entire human transcriptome. Surprisingly, this model revealed a new role of codon usage in regulating translation termination, which was experimentally validated. We also identified thousands of new open reading frames in mRNAs or lncRNAs, some of which were confirmed experimentally. The model trained with human mRNAs achieved high prediction accuracy of canonical translation sites in all eukaryotes and good prediction in polycistronic transcripts from prokaryotes or RNA viruses, suggesting a high degree of conservation in translation control. Collectively, we present a general and efficient deep learning model for RNA translation, generating new insights into the complexity of translation regulation.

Cell biology: Converging paths to cohesion

Cohesin holds together the sister chromatids from DNA replication onwards. How cohesion is established has long remained a black box. Through recent studies, a model is emerging in which a replisome-cohesin encounter results in the establishment of cohesive linkages at sites of replication termination.

Where Do Core Thalamocortical Axons Terminate in Mammalian Neocortex When There Is No Cytoarchitecturally Distinct Layer 4?

Although the mammalian cerebral cortex is most often described as a hexalaminar structure, there are cortical areas (primary motor cortex) and species (elephants, cetaceans, and hippopotami), where a cytoarchitecturally indistinct, or absent, layer 4 is noted. Thalamocortical projections from the core, or first order, thalamic system terminate primarily in layers 4/inner 3. We explored the termination sites of core thalamocortical projections in cortical areas and in species where there is no cytoarchitecturally distinct layer 4 using the immunolocalization of vesicular glutamate transporter 2, a known marker of core thalamocortical axon terminals, in 31 mammal species spanning the eutherian radiation. Several variations from the canonical cortical column outline of layer 4 and core thalamocortical inputs were noted. In shrews/microchiropterans, layer 4 was present, but many core thalamocortical projections terminated in layer 1 in addition to layers 4 and inner 3. In primate primary visual cortex, the sublaminated layer 4 was associated with a specialized core thalamocortical projection pattern. In primate primary motor cortex, no cytoarchitecturally distinct layer 4 was evident and the core thalamocortical projections terminated throughout layer 3. In the African elephant, cetaceans, and river hippopotamus, no cytoarchitecturally distinct layer 4 was observed and core thalamocortical projections terminated primarily in inner layer 3 and less densely in outer layer 3. These findings are contextualized in terms of cortical processing, perception, and the evolutionary trajectory leading to an indistinct or absent cortical layer 4.

Deletion of the 3′ End of the Introduced cry1Ac Gene Retains the Insecticidal Activity in Transgenic Cotton

The structure and expression of exogenous genes in transgenic crops are critical for the target traits. R7569 has the same exogenous insertion structure as the transgenic insect-resistant cotton MON531 but with a deletion in the 3′ end of the cry1Ac gene and the terminator region. Thus, in the present study, transcription, expression, and insecticidal activity assays were conducted to determine the function of the truncated cry1Ac gene. R7569 has a truncated cry1Ac gene with a length of 2554 bp encoding 881 amino acids, and the transcription termination site was mainly concentrated downstream of the truncated position and extended 160–270 bp from the truncated position using rapid amplification of cDNA ends (RACE). The transcript levels of the cry1Ac gene in R7569 were significantly higher than those of MON531 implants, except for during the boll stage. The content of the Cry1Ac protein in R7569 was higher than that of MON531 in the cotton leaf in all three periods. The corrected mortality rates of R7569 and MON531 against bollworms were 93.09% and 88.83%, respectively. The LC50 value of R7569 was 0.732 ng/g (dw), indicating a high level of resistance to bollworm. In this study, for the first time, we found a partial deletion of the target gene in commercially applied transgenic crops, and the partial deletion of the 3′ end of the cry1Ac gene retained a better transcription, expression level, and insecticidal activity, which can provide a specific case for the safety evaluation of transgenic crops.

Hexagonal Halide Perovskite Cs2LiInCl6: Cation Ordering, Face-Shared Octahedral Trimers and Mn2+ Luminescence.

The In-based double perovskite halides have been widely studied for promising optical-electric applications. The halide hexagonal perovskite Cs2LiInCl6 was isolated using solid-state reactions and investigated using X-ray diffraction and solid-state NMR spectra. The material adopts a 12-layered hexagonal structure (12R) consisting of layered cationic orders driven by the cationic charge difference and has Li+ cations in the terminal site and In3+ in the central site of face-shared octahedron trimers. Such a cationic ordering pattern is stabilized by electrostatic repulsions between the next-nearest neighboring cations in the trimers. The LiCl6 octahedron displays large distortion and is confirmed by 7Li SSNMR in the Cs2LiInCl6. The Cs2LiInCl6 material has a direct bandgap of ~4.98 eV. The Cs2LiInCl6: Mn2+ displays redshift luminescence (centered at ~610-622 nm) from the substituted Mn2+ emission in octahedron with larger PLQY (17.8 %-48 %) compared with that of Cs2NaInCl6: Mn2+. The Mn-doped materials show luminescent concentration quenching and thermal quenching. The composition Cs2Li0.99In0.99Mn0.02Cl6 exhibits the highest PL intensity, a maximum PLQY of 48 %, and high luminescent retention rate of ~86 % below 400 K and is suitable for application for pc-LED. These findings contribute to our understanding of the chloride perovskites and hold potential for widespread optical applications.

Identification of antennal alternative splicing by combining genome and full-length transcriptome analysis in Bactrocera dorsalis.

Alternative splicing is an essential post-transcriptional regulatory mechanism that diversifies gene function by generating multiple protein isoforms from a single gene and act as a crucial role in insect environmental adaptation. Olfaction, a key sense for insect adaptation, relies heavily on the antennae, which are the primary olfactory organs expressing most of the olfactory genes. Despite the extensive annotation of olfactory genes within insect antennal tissues facilitated by high-throughput sequencing technology advancements, systematic analyses of alternative splicing are still relatively less. In this study, we focused on the oriental fruit fly (Bactrocera dorsalis), a significant pest of fruit crops. We performed a detailed analysis of alternative splicing in its antennae by utilizing the full-length transcriptome of its antennal tissue and the insect's genome. The results revealed 8600 non-redundant full-length transcripts identified in the oriental fruit fly antennal full-length transcriptome, spanning 4,145 gene loci. Over 40% of these loci exhibited multiple isoforms. Among these, 161 genes showed sex-biased isoform switching, involving seven different types of alternative splicing. Notably, events involving alternative transcription start sites (ATSS) and alternative transcription termination sites (ATTS) were the most common. Of all the genes undergoing ATSS and ATTS alternative splicing between male and female, 32 genes were alternatively spliced in protein coding regions, potentially affecting protein function. These genes were categorized based on the length of the sex-biased isoforms, with the highest difference in isoform fraction (dIF) associated with the ATSS type, including genes such as BdorABCA13, BdorCAT2, and BdorTSN3. Additionally, transcription factor binding sites for doublesex were identified upstream of both BdorABCA13 and BdorCAT2. Besides being expressed in the antennal tissues, BdorABCA13 and BdorCAT2 are also expressed in the mouthparts, legs, and genitalia of both female and male adults, suggesting their functional diversity. This study reveals alternative splicing events in the antennae of Bactrophora dorsalis from two aspects: odorant receptor genes and other types of genes expressed in the antennae. This study not only provides a research foundation for understanding the regulation of gene function by alternative splicing in the oriental fruit fly but also offers new insights for utilizing olfaction-based behavioral manipulation techniques to manage this pest.

Dormant origin firing promotes head-on transcription-replication conflicts at transcription termination sites in response to BRCA2 deficiency

BRCA2 is a tumor suppressor protein responsible for safeguarding the cellular genome from replication stress and genotoxicity, but the specific mechanism(s) by which this is achieved to prevent early oncogenesis remains unclear. Here, we provide evidence that BRCA2 acts as a critical suppressor of head-on transcription-replication conflicts (HO-TRCs). Using Okazaki-fragment sequencing (Ok-seq) and computational analysis, we identified origins (dormant origins) that are activated near the transcription termination sites (TTS) of highly expressed, long genes in response to replication stress. Dormant origins are a source for HO-TRCs, and drug treatments that inhibit dormant origin firing led to a reduction in HO-TRCs, R-loop formation, and DNA damage. Using super-resolution microscopy, we showed that HO-TRC events track with elongating RNA polymerase II, but not with transcription initiation. Importantly, RNase H2 is recruited to sites of HO-TRCs in a BRCA2-dependent manner to help alleviate toxic R-loops associated with HO-TRCs. Collectively, our results provide a mechanistic basis for how BRCA2 shields against genomic instability by preventing HO-TRCs through both direct and indirect means occurring at predetermined genomic sites based on the pre-cancer transcriptome.

Nucleosomal DNA has topological memory

One elusive aspect of the chromosome architecture is how it constrains the DNA topology. Nucleosomes stabilise negative DNA supercoils by restraining a DNA linking number difference (∆Lk) of about −1.26. However, whether this capacity is uniform across the genome is unknown. Here, we calculate the ∆Lk restrained by over 4000 nucleosomes in yeast cells. To achieve this, we insert each nucleosome in a circular minichromosome and perform Topo-seq, a high-throughput procedure to inspect the topology of circular DNA libraries in one gel electrophoresis. We show that nucleosomes inherently restrain distinct ∆Lk values depending on their genomic origin. Nucleosome DNA topologies differ at gene bodies (∆Lk = −1.29), intergenic regions (∆Lk = −1.23), rDNA genes (∆Lk = −1.24) and telomeric regions (∆Lk = −1.07). Nucleosomes near the transcription start and termination sites also exhibit singular DNA topologies. Our findings demonstrate that nucleosome DNA topology is imprinted by its native chromatin context and persists when the nucleosome is relocated.

Readon: a novel algorithm to identify read-through transcripts with long-read sequencing data.

There are many clustered transcriptionally active regions in the human genome, in which the transcription complex cannot immediately terminate transcription at the upstream gene termination site, but instead continues to transcribe intergenic regions and downstream genes, resulting in read-through transcripts. Several studies have demonstrated the regulatory roles of read-through transcripts in tumorigenesis and development. However, limited by the read length of next-generation sequencing, discovery of read-through transcripts has been slow. For long but also erroneous third-generation sequencing data, this study developed a novel minimizer sketch algorithm to accurately and quickly identify read-through transcripts. Readon initially splits the reference sequence into distinct active regions. It employs a sliding window approach within each region, calculates minimizers, and constructs the specialized structured arrays for query indexing. Following initial alignment anchor screening of candidate read-through transcripts, further confirmation steps are executed. Comparative assessments against existing software reveal Readon's superior performance on both simulated and validated real data. Additionally, two downstream tools are provided: one for predicting whether a read-through transcript is likely to undergo nonsense-mediated decay or encodes a protein, and another for visualizing splicing patterns. Readon is freely available on GitHub (https://github.com/Bulabula45/Readon).

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

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

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

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

Focal pulsed field ablation in complex cases of atrial tachycardia - feasibility, outcome and safety of a novel technology

Abstract Introduction The importance of pulsed-field ablation (PFA) is rising in the field of catheter ablation. Nevertheless, the use of a single-shot devices is limited to pulmonary vein isolation (PVI). Thus, significance of technologies implementing point-by-point PFA is growing. A commercially available system uses radiofrequency (RF) catheters in combination with a PFA-generator. Data on the use is sparse, especially for treating atrial tachycardia (AT). The aim of this study was to evaluate feasibility, safety and mid-term outcomes of point-by-point PFA in complex cases of AT. Methods All consecutive patients treated with a focal PFA-catheter (N = 34) suffering from AT were included. A high density map was created in all patients. Established RF catheters were employed as PFA catheters with the PFA generator. Except for the ablation generator, the standard setting at our clinic for ablation of AT was not changed. In case of sinus rhythm at the beginning, burst stimulation was performed in order to induce the clinical AT. Acute procedure success was defined as creation of ablation lesions preventing the mechanism of the clinical tachycardia and/or non-inducibility of the clinical AT. Outcome and safety was evaluated during the hospital stay and visits at our outpatient clinic, including 7d-Holter-ECG. Results In all 34 included patients, acute procedure success was achieved. Baseline characteristics are listed in table 1. In average, patients had 1,21 ± 0,88 ablations before, 67,6% of patients had linear lesions in the past. Mean procedure duration was 102,7 ± 30,3 min, the LA dwell time was 75,0 ± 24,7 min (table 2). Any desired lesion set was accomplished (pulmonary vein isolation, linear lesions or ablation of focal AT/localized reentry) with the focal PFA technology. Linear lesions were ablated in 32 (94,1%) patients, while a pulmonary vein isolation was performed in 12 patients (35,3%). Ablation of localized reentries was necessary in two patients (5,9%). In total, 51 linear lesions were created: 27 anterior lines, 18 roof lines, 5 CTI-lines and one posterior box; bidirectional block was proven in all cases. Furthermore, three patients suffered a macro-reentry due to reconnected pulmonary veins. The site of termination of the tachycardia is shown in Figure 1. No procedure-related minor or major complications occurred (no groin complications, no stroke, no pericardial tamponade). After a mean follow-up of 179,4 ± 107,8 days, 8 patients (23,5%) suffered a recurrence of any atrial arrhythmia. Conclusion Applying focal PFA with well-known radiofrequency ablation catheters is safe and efficient, also in cases of atrial tachycardia. The integration of the new system into clinical practice is feasible and did not prolong the procedures. Acute procedure success was achieved in all cases. For further evaluation of efficacy and safety, a control group of patients treated with radiofrequency or a randomized trial is needed.