Reciprocal regulation of T follicular helper cells and dendritic cells drives colitis development.

The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (TFH) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and TFH cells was found within T cell zones of colonic lymphoid follicles. TFH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted TFH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, TFH cells transdifferentiated into long-lived pathogenic TH1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of TFH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis.

Structural Insights into Non-canonical Ubiquitination Catalyzed by SidE.

Ubiquitination constitutes one of the most important signaling mechanisms in eukaryotes. Conventional ubiquitination is catalyzed by the universally conserved E1-E2-E3 three-enzyme cascade in an ATP-dependent manner. The newly identified SidE family effectors of the pathogen Legionella pneumophila ubiquitinate several human proteins by a different mechanism without engaging any of the conventional ubiquitination machinery. We now report the crystal structures of SidE alone and in complex with ubiquitin, NAD, and ADP-ribose, thereby capturing different conformations of SidE before and after ubiquitin and ligand binding. The structures of ubiquitin bound to both mART and PDE domains reveal several unique features of the two reaction steps catalyzed by SidE. Further, the structural and biochemical results demonstrate that SidE family members do not recognize specific structural folds of the substrate proteins. Our studies provide both structural explanations for the functional observations and new insights into the molecular mechanisms of this non-canonical ubiquitination machinery.

Viral tegument proteins restrict cGAS-DNA phase separation to mediate immune evasion.

DNA-induced liquid-liquid phase separation of cyclic GMP-AMP synthase (cGAS) triggers a potent response to detect pathogen infection and promote innate immune signaling. Whether and how pathogens manipulate cGAS-DNA condensation to mediate immune evasion is unknown. We report the identification of a structurally related viral tegument protein family, represented by ORF52 and VP22 from gamma- and alpha-herpesvirinae, respectively, that employs a conserved mechanism to restrict cGAS-DNA phase separation. ORF52/VP22 proteins accumulate into, and effectively disrupt, the pre-formed cGAS-DNA condensation both in vitro and in cells. The inhibition process is dependent on DNA-induced liquid-liquid phase separation of the viral protein rather than a direct interaction with cGAS. Moreover, highly abundant ORF52 proteins carried within viral particles are able to target cGAS-DNA phase separation in early infection stage. Our results define ORF52/VP22-type tegument proteins as a family of inhibitors targeting cGAS-DNA phase separation and demonstrate a mechanism for how viruses overcome innate immunity.

The Transcription Factor Tox2 Drives T Follicular Helper Cell Development via Regulating Chromatin Accessibility.

T follicular helper (Tfh) cells provide essential help to B cells in germinal center (GC) reactions. Bcl6 is the obligatory lineage transcription factor in Tfh cells. Here, we examined the molecular pathways that induce Bcl6 gene expression and underscore Bcl6-dependent function during Tfh cell commitment. Integration of genome-wide Bcl6 occupancy in Tfh cells and differential gene expression analyses suggested an important role for the transcription factor Tox2 in Tfh cell differentiation. Ectopic expression of Tox2 was sufficient to drive Bcl6 expression and Tfh development. In genome-wide ChIP-seq analyses, Tox2-bound loci associated with Tfh cell differentiation and function, including Bcl6. Tox2 binding was associated with increased chromatin accessibility at these sites, as measured by ATAC-seq. Tox2-/- mice exhibited defective Tfh differentiation, and inhibition of both Tox2 and the related transcription factor Tox abolished Tfh differentiation. Thus, a Tox2-Bcl6 axis establishes a transcriptional feed-forward loop that promotes the Tfh program.

Diverse Mechanisms of CRISPR-Cas9 Inhibition by Type IIC Anti-CRISPR Proteins.

Anti-CRISPR proteins (Acrs) targeting CRISPR-Cas9 systems represent natural "off switches" for Cas9-based applications. Recently, AcrIIC1, AcrIIC2, and AcrIIC3 proteins were found to inhibit Neisseria meningitidis Cas9 (NmeCas9) activity in bacterial and human cells. Here we report biochemical and structural data that suggest molecular mechanisms of AcrIIC2- and AcrIIC3-mediated Cas9 inhibition. AcrIIC2 dimer interacts with the bridge helix of Cas9, interferes with RNA binding, and prevents DNA loading into Cas9. AcrIIC3 blocks the DNA loading step through binding to a non-conserved surface of the HNH domain of Cas9. AcrIIC3 also forms additional interactions with the REC lobe of Cas9 and induces the dimerization of the AcrIIC3-Cas9 complex. While AcrIIC2 targets Cas9 orthologs from different subtypes, albeit with different efficiency, AcrIIC3 specifically inhibits NmeCas9. Structure-guided changes in NmeCas9 orthologs convert them into anti-CRISPR-sensitive proteins. Our studies provide insights into anti-CRISPR-mediated suppression mechanisms and guidelines for designing regulatory tools in Cas9-based applications.

A cardiotoxicity-eliminated ACE2 variant as a pan-inhibitor against coronavirus cell invasion.

Human recombinant ACE2 (hrACE2) has been highly anticipated as a successful COVID-19 treatment; however, its potential to cause cardiac side effects has given rise to many concerns. Here, we developed a cardiotoxicity-eliminated hrACE2 variant, which had four mutation sites within hrACE2 (H345L, H374L, H378L, H505L) and was named as hrACE2-4mu. hrACE2-4mu has a consistent binding affinity with the variant SARS-CoV-2 spike proteins (SPs) and an efficient ability to block SP-induced SARS-CoV-2 entry into cells. In golden hamsters, injection of purified wild-type (WT) hrACE2 rescues the early stages of pneumonia caused by the SPs of the WT, delta, and omicron variants with reduced inflammatory cell infiltration. However, long-term injection of WT hrACE2 induces undesired cardiac fibrosis, as demonstrated by upregulated fibronectin and collagen expression. Our newly developed hrACE2-4mu showed similar protective abilities against a series of coronavirus cell invasions as WT hrACE2, meanwhile it did not cause apparent cardiac side effects. Thus, we generated a cardiotoxicity-eliminated variant of hrACE2 as a pan-inhibitor against coronavirus cell invasion, providing a potential novel strategy for the treatment of COVID-19 and other coronaviruses.

Lesion monitoring parameters as predictors of atrial arrhythmia recurrence after catheter ablation in persistent AF: A DECAAF II sub-analysis.

BACKGROUND: The formation of transmural lesions is necessary for the ablation of persistent atrial fibrillation (prAF). Ablation index (AI) and generator impedance drop (ID) predict lesion size but their correlation with long-term outcomes in prAF is not known. Furthermore, we proposed a new parameter, efficacy ratio (ER) calculated as ID/AI, to gain indirect insight into the role of factors affecting ID but not considered by AI. METHODS: We included ablations performed during the DECAAF II trial if they had uploaded lesion-by-lesion summary data and were performed with radiofrequency catheters on the CARTO system. Average patient-level parameters were calculated from all generated Vizitags. RESULTS: A total of 427 ablations met inclusion criteria and 166 utilized AI. Analyzed as continuous variables, ID and ER predicted long-term arrhythmia-free survival but not AI. The ideal cut-off for ID was ID ≥ 10.4 ohms and had a C-index of 0.55. It predicted reduced risk of arrhythmia: hazard ratio 0.56 [0.36-0.88], p = .013 (arrhythmia-free survival of 67% vs. 52%). Similarly, an ER of 1.7 ohms/100AI had a C-index of 0.58 and predicted reduced arrhythmia recurrence: HR 0.39 [0.22-0.69], p = .001. ER < 1.7 ohms/100AI was related to just 32% arrhythmia-free survival. ER improved prognostication as compared to ID alone and identified a subset of low ID patients with even worse outcomes. CONCLUSION: Average ID was predictive of improved outcomes following ablation of prAF. The ratio of ID/AI (ER) was postulated as a measure to summarize the overall impact of factors not considered in the AI formula and provided improved prognostication.

Body mass index as a determinant of scar formation post-AF ablation: Insights from DECAAF II.

INTRODUCTION: Obesity is implicated in adverse atrial remodeling and worse outcomes in patients with atrial fibrillation. The objective of this study is to assess the effect of body mass index (BMI) on ablation-induced scar formation on late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR). METHODS: We conducted an analysis of DECAAF II participants who underwent LGE-CMR scans to measure scar formation 3 months after catheter ablation. Ablation parameters and lesion delivery were not dependent on BMI. The effect of BMI on ablation success was explored. RESULTS: Our analyses included 811 patients. Comorbidities were more prevalent in obese patients. Baseline left atrial volume was higher in obese individuals, 118, 126, 135, 140, and 143 mm3 for normal weight, overweight, obese grade 1, 2, and 3, respectively (p < .001). BMI was associated with scar formation (R = -0.135, p < .001), with patients with Class 3 obesity having the lowest percentage of ablation-induced scar, 11.1%, 10.3%, 9.5%, 8.8%, 6.8% by ascending BMI group. There was an inverse correlation between BMI and the amount of fibrosis covered by ablation scar, 24%, 23%, 21%, and 18% by ascending BMI group (p = .001). For the fibrosis-guided ablation group, BMI was associated with residual fibrosis (R = 0.056, p = .005). CONCLUSION: Obese patients have lower ablation scar formation, covered fibrosis, and more residual fibrosis postablation compared to nonobese patients, regardless of ablation parameters including impedance drop.

Biomechanical evaluation of flash-frozen and cryo-sectioned papillary muscle samples by using sinusoidal analysis: cross-bridge kinetics and the effect of partial Ca2+ activation.

We examined the integrity of flash-frozen and cryo-sectioned cardiac muscle preparations (introduced by Feng and Jin, 2020) by assessing tension transients in response to sinusoidal length changes at varying frequencies (1-100 Hz) at 25 °C. Using 70-µm-thick sections, we isolated fiber preparations to study cross-bridge (CB) kinetics: preparations were activated by saturating Ca2+ as well as varying concentrations of ATP and phosphate (Pi). Our results showed that, compared to ordinary skinned fibers, in-series stiffness decreased to 1/2, which resulted in a decrease of isometric tension to 62%, but CB kinetics and Ca2+ sensitivity were little affected. The pCa study demonstrated that the rate constant of the force generation step (2πb) is proportionate to [Ca2+] at < 5 µM, suggesting that the activation mechanism can be described by a simple second order reaction. We also found that tension, stiffness, and magnitude parameters are related to [Ca2+] by the Hill equation, with a cooperativity coefficient of 4-5, which is consistent with the fact that Ca2+ activation mechanisms involve cooperative multimolecular interactions. Our results support the long-held hypothesis that Process C (Phase 2) represents the CB detachment step, and Process B (Phase 3) represents the force generation step. Moreover, we discovered that constant H may represent the work-performing step in cardiac preparations. Our experiments demonstrate excellent CB kinetics with two well-defined exponentials that can be more distinguished than those found using ordinary skinned fibers. Flash-frozen and cryo-sectioned preparations are especially suitable for multi-institutional collaborations nationally and internationally because of their ease of transportation.

Gene expression profiles, potential targets and treatments of cardiac remodeling.

Hypertensive and ischemic heart diseases have high morbidity all over the world, and they primarily contribute to heart failure associated with high mortality. Cardiac remodeling, as a basic pathological process in heart diseases, is mainly comprised of cardiac hypertrophy and fibrosis, as well as cell death which occurs especially in the ischemic cardiomyopathy. Myocardial remodeling has been widely investigated by a variety of animal models, including pressure overload, angiotensin II stimulation, and myocardial infarction. Pressure overload can cause compensatory cardiac hypertrophy at the early stage, followed by decompensatory hypertrophy and heart failure at the end. Recently, RNA sequencing and differentially expressed gene (DEG) analyses have been extensively employed to elucidate the molecular mechanisms of cardiac remodeling and related heart failure, which also provide potential targets for high-throughput drug screenings. In this review, we summarize recent advancements in gene expression profiling, related gene functions, and signaling pathways pertinent to myocardial remodeling induced by pressure overload at distinct stages, ischemia-reperfusion, myocardial infarction, and diabetes. We also discuss the effects of sex differences and inflammation on DEGs and their transcriptional regulatory mechanisms in cardiac remodeling. Additionally, we summarize emerging therapeutic agents and strategies aimed at modulating gene expression profiles during myocardial remodeling.

Blocking MG53S255 Phosphorylation Protects Diabetic Heart From Ischemic Injury.

BACKGROUND: As an integral component of cell membrane repair machinery, MG53 (mitsugumin 53) is important for cardioprotection induced by ischemia preconditioning and postconditioning. However, it also impairs insulin signaling via its E3 ligase activity-mediated ubiquitination-dependent degradation of IR (insulin receptor) and IRS1 (insulin receptor substrate 1) and its myokine function-induced allosteric blockage of IR. Here, we sought to develop MG53 into a cardioprotection therapy by separating its detrimental metabolic effects from beneficial actions. METHODS: Using immunoprecipitation-mass spectrometry, site-specific mutation, in vitro kinase assay, and in vivo animal studies, we investigated the role of MG53 phosphorylation at serine 255 (S255). In particular, utilizing recombinant proteins and gene knock-in approaches, we evaluated the potential therapeutic effect of MG53-S255A mutant in treating cardiac ischemia/reperfusion injury in diabetic mice. RESULTS: We identified S255 phosphorylation as a prerequisite for MG53 E3 ligase activity. Furthermore, MG53S255 phosphorylation was mediated by GSK3ß (glycogen synthase kinase 3 beta) and markedly elevated in the animal models with metabolic disorders. Thus, IR-IRS1-GSK3ß-MG53 formed a vicious cycle in the pathogenesis of metabolic disorders where aberrant insulin signaling led to hyper-activation of GSK3ß, which in turn, phosphorylated MG53 and enhanced its E3 ligase activity, and further impaired insulin sensitivity. Importantly, S255A mutant eliminated the E3 ligase activity while retained cell protective function of MG53. Consequently, the S255A mutant, but not the wild type MG53, protected the heart against ischemia/reperfusion injury in db/db mice with advanced diabetes, although both elicited cardioprotection in normal mice. Moreover, in S255A knock-in mice, S255A mutant also mitigated ischemia/reperfusion-induced myocardial damage in the diabetic setting. CONCLUSIONS: S255 phosphorylation is a biased regulation of MG53 E3 ligase activity. The MG53-S255A mutant provides a promising approach for the treatment of acute myocardial injury, especially in patients with metabolic disorders.

Joint modeling approaches for censored predictors due to detection limits with applications to metabolites data.

Measures of substance concentration in urine, serum or other biological matrices often have an assay limit of detection. When concentration levels fall below the limit, exact measures cannot be obtained, and thus are left censored. The problem becomes more challenging when the censored data come from heterogeneous populations consisting of exposed and non-exposed subjects. If the censored data come from non-exposed subjects, their measures are always zero and hence censored, forming a latent class governed by a distinct censoring mechanism compared with the exposed subjects. The exposed group's censored measurements are always greater than zero, but less than the detection limit. It is very often that the exposed and non-exposed subjects may have different disease traits or different relationships with outcomes of interest, so we need to disentangle the two different populations for valid inference. In this article, we aim to fill the methodological gaps in the literature by developing a novel joint modeling approach to not only address the censoring issue in predictors, but also untangle different relationships of exposed and non-exposed subjects with the outcome. Simulation studies are performed to assess the numerical performance of our proposed approach when the sample size is small to moderate. The joint modeling approach is also applied to examine associations between plasma metabolites and blood pressure in Bogalusa Heart Study, and identify new metabolites that are highly associated with blood pressure.

Life's Essential 8, Genetic Susceptibility, and Incident Cardiovascular Disease: A Prospective Study.

BACKGROUND: The American Heart Association recently released a new cardiovascular health (CVH) metric, Life's Essential 8 (LE8), for health promotion. However, the association between levels of LE8 and the risk of cardiovascular disease (CVD) outcomes is not known from a large prospective cohort. We aim to analyze the relationship between CVH, indicated by LE8, and risks of coronary heart disease (CHD), stroke, and CVD. Moreover, we sought to test whether the genetic susceptibility to CHD or stroke could be modified by LE8. METHODS: A total of 137 794 participants free of CVD from the UK Biobank were included. CVH was scored using LE8 and categorized as low, moderate, and high. RESULTS: During a median of 10 years, 8595 CVD cases (6968 CHDs and 1948 strokes) were documented. A higher LE8 score was associated with remarkably lower risks of CHD, stroke, and CVD (P<0.001 for all). Comparing the high CVH to the low CVH, the hazard ratios (95% CI) were 0.34 (0.30-0.38) for CHD, 0.45 (0.37-0.54) for stroke, and 0.36 (0.33-0.40) for CVD. Moreover, the model with LE8 achieved higher accuracy and outperformed the model with Life's Simple 7 for CHD, stroke, and CVD (P<0.001 for all). The protective associations of the LE8 score with CVD outcomes were more pronounced among women (P interaction, <0.001 for CHD and 0.0013 for CVD, respectively) and among younger adults (P interaction, <0.001, 0.007, and <0.001 for CHD, stroke, and CVD, respectively). In addition, a significant interaction was found between the genetic risk of CHD and the LE8 score (P interaction, <0.001). The inverse association was stronger among those with a lower genetic risk of CHD. CONCLUSIONS: High level of CVH, defined by LE8, was associated with significantly lower risks of CHD, stroke, and CVD.

Silver Nanoparticle-Loaded Titanium-Based Metal-Organic Framework for Promoting Antibacterial Performance by Synergistic Chemical-Photodynamic Therapy.

The abuse of antibiotics leads to an increasing emergence of drug-resistant bacteria, which not only causes a waste of medical resources but also seriously endangers people's health and life safety. Therefore, it is highly desirable to develop an efficient antibacterial strategy to reduce the reliance on traditional antibiotics. Antibacterial photodynamic therapy (aPDT) is regarded as an intriguing antimicrobial method that is less likely to generate drug resistance, but its efficiency still needs to be further improved. Herein, a robust titanium-based metal-organic framework ACM-1 was adopted to support Ag nanoparticles (NPs) to obtain Ag NPs@ACM-1 for boosting antibacterial efficiency via synergistic chemical-photodynamic therapy. Apart from the intrinsic antibacterial nature, Ag NPs largely boost ROS production and thus improve aPDT efficacy. As a consequence, Ag NPs@ACM-1 shows excellent antibacterial activity under visible light illumination, and its minimum bactericidal concentrations (MBCs) against E. coli, S. aureus, and MRSA are as low as 39.1, 39.1, and 62.5 µg mL-1, respectively. Moreover, to expand the practicability of Ag NPs@ACM-1, two (a dense and a loose) Ag NPs@ACM-1 films were readily fabricated by simply dispersing Ag NPs@ACM-1 into heated aqueous solutions of edible agar and sequentially cooling through heating or freeze-drying, respectively. Notably, these two films are mechanically flexible and exhibit excellent antibacterial activities, and their antimicrobial performances can be well retained in their recyclable and remade films. As agar is nontoxic, degradable, inexpensive, and ecosustainable, the dense and loose Ag NPs@ACM-1 films are potent to serve as recyclable and degradable antibacterial plastics and antibacterial dressings, respectively.

Comprehensive atrial fibrillation burden and symptom reduction post-ablation: insights from DECAAF II.

AIMS: Traditional atrial fibrillation (AF) recurrence after catheter ablation is reported as a binary outcome. However, a paradigm shift towards a more granular definition, considering arrhythmic or symptomatic burden, is emerging. We hypothesize that ablation reduces AF burden independently of conventional recurrence status in patients with persistent AF, correlating with symptom burden reduction. METHODS AND RESULTS: Ninety-eight patients with persistent AF from the DECAAF II trial with pre-ablation follow-up were included. Patients recorded daily single-lead electrocardiogram (ECG) strips, defining AF burden as the proportion of AF days among total submitted ECG days. The primary outcome was atrial arrhythmia recurrence. The AF severity scale was administered pre-ablation and at 12 months post-ablation. At follow-up, 69 patients had atrial arrhythmia recurrence and 29 remained in sinus rhythm. These patients were categorized into a recurrence (n = 69) and a no-recurrence group (n = 29). Both groups had similar baseline characteristics, but recurrence patients were older (P = 0.005), had a higher prevalence of hyperlipidaemia (P = 0.007), and had a larger left atrial (LA) volume (P = 0.01). There was a reduction in AF burden in the recurrence group when compared with their pre-ablation burden (65 vs. 15%, P < 0.0001). Utah Stage 4 fibrosis and diabetes predicted less improvement in AF burden. The symptom severity score at 12 months post-ablation was significantly reduced compared with the pre-ablation score in the recurrence group, and there was a significant correlation between the reduction in symptom severity score and the reduction in AF burden (R = 0.39, P = 0.001). CONCLUSION: Catheter ablation reduces AF burden, irrespective of arrhythmia recurrence post-procedure. There is a strong correlation between AF burden reduction and symptom improvement post-ablation. Notably, elevated LA fibrosis impedes AF burden decrease following catheter ablation.

Differences in postablation cardiac MRI scar between radiofrequency and cryoballoon ablation: A DECAAF II subanalysis.

INTRODUCTION: Pulmonary vein isolation (PVI) using radiofrequency (RF) and cryoballoon (Cryo) ablation are standard approaches for rhythm control in patients with symptomatic atrial fibrillation. Both strategies create scars in the left atrium (LA). There have been few studies investigating the difference in scar formation between patients undergoing RF and Cryo using cardiac magnetic resonance (CMR) imaging. METHODS: The current study is a subanalysis of the control arm of the Delayed-Enhancement MRI Determinant of Successful Catheter Ablation of Atrial Fibrillation study (DECAAF II). The study was a multicenter, randomized, controlled, single-blinded trial that evaluated atrial arrhythmia recurrence (AAR) between PVI alone and PVI plus CMR atrial fibrosis-guided ablation. Preablation CMR and 3- to 6-month postablation CMR were obtained to assess baseline LA fibrosis and scar formation, respectively. RESULTS: Of the 843 patients randomized in the DECAAF II trial, we analyzed the 408 patients in the primary analysis control arm that received standard PVI. Five patients received combined RF and Cryo ablations, so they were excluded from this subanalysis. Of the 403 patients analyzed, 345 underwent RF and 58 Cryo. The average procedure duration was 146 min for RF and 103 min for Cryo (p = .001). The rate of AAR at ~15 months occurred in 151 (43.8%) patients in the RF group and 28 (48.3%) patients in the Cryo group (p = .62). On 3-month post-CMR, the RF arm had significantly more scar (8.8% vs. 6.4%, p = .001) compared to Cryo. Patients with ≥6.5% LA scar (p < .001) and ≥2.3% LA scar around the PV antra (p = .01) on 3-month post-CMR had less AAR independent of the ablation technique. Cryo caused a greater percentage of right and left pulmonary vein (PV) antral scar (p = .04, p = .02) and less non-PV antral scar (p = .009) compared to RF. On Cox regression, Cryo patients free of AAR had a greater percentage of left PV antral scar (p = .01) and less non-PV antral scar (p = .004) compared to RF free of AAR. CONCLUSION: In this subanalysis of the control arm of the DECAAF II trial, we observed that Cryo formed a more significant percentage of PV antral scar and less non-PV antral scar compared to RF. Post ablation LA scar ≥6.5% predicted freedom from AAR, independent of ablation technique. These findings may have prognostic implications in ablation technique selection and freedom from AAR.

Generalization Analysis of Pairwise Learning for Ranking With Deep Neural Networks.

Pairwise learning is widely employed in ranking, similarity and metric learning, area under the ROC curve (AUC) maximization, and many other learning tasks involving sample pairs. Pairwise learning with deep neural networks was considered for ranking, but enough theoretical understanding about this topic is lacking. In this letter, we apply symmetric deep neural networks to pairwise learning for ranking with a hinge loss ϕh and carry out generalization analysis for this algorithm. A key step in our analysis is to characterize a function that minimizes the risk. This motivates us to first find the minimizer of ϕh-risk and then design our two-part deep neural networks with shared weights, which induces the antisymmetric property of the networks. We present convergence rates of the approximation error in terms of function smoothness and a noise condition and give an excess generalization error bound by means of properties of the hypothesis space generated by deep neural networks. Our analysis is based on tools from U-statistics and approximation theory.

Effect of fibrosis regionality on atrial fibrillation recurrence: insights from DECAAF II.

AIMS: The amount of fibrosis in the left atrium (LA) predicts atrial fibrillation (AF) recurrence after catheter ablation (CA). We aim to identify whether regional variations in LA fibrosis affect AF recurrence. METHODS AND RESULTS: This post hoc analysis of the DECAAF II trial includes 734 patients with persistent AF undergoing first-time CA who underwent late gadolinium enhancement magnetic resonance imaging (LGE-MRI) within 1 month prior to ablation and were randomized to MRI-guided fibrosis ablation in addition to standard pulmonary vein isolation (PVI) or standard PVI only. The LA wall was divided into seven regions: anterior, posterior, septal, lateral, right pulmonary vein (PV) antrum, left PV antrum, and left atrial appendage (LAA) ostium. Regional fibrosis percentage was defined as a region's fibrosis prior to ablation divided by total LA fibrosis. Regional surface area percentage was defined as an area's surface area divided by the total LA wall surface area before ablation. Patients were followed up for a year with single-lead electrocardiogram (ECG) devices. The left PV had the highest regional fibrosis percentage (29.30 ± 14.04%), followed by the lateral wall (23.23 ± 13.56%), and the posterior wall (19.80 ± 10.85%). The regional fibrosis percentage of the LAA was a significant predictor of AF recurrence post-ablation (odds ratio = 1.017, P = 0.021), and this finding was only preserved in patients receiving MRI-guided fibrosis ablation. Regional surface area percentages did not significantly affect the primary outcome. CONCLUSION: We have confirmed that atrial cardiomyopathy and remodelling are not a homogenous process, with variations in different regions of the LA. Atrial fibrosis does not uniformly affect the LA, and the left PV antral region has more fibrosis than the rest of the wall. Furthermore, we identified regional fibrosis of the LAA as a significant predictor of AF recurrence post-ablation in patients receiving MRI-guided fibrosis ablation in addition to standard PVI.

Identifying the prognostic significance of early arrhythmia recurrence during the blanking period and the optimal blanking period duration: insights from the DECAAF II study.

OBJECTIVE: Early atrial arrhythmia recurrence following atrial fibrillation (AF) ablation is common. Current guidelines promulgate a 3-month blanking period. We hypothesize that early atrial arrhythmia recurrence during the blanking period may predict longer-term ablation outcomes. METHODS AND RESULTS: A total of 688 patients with persistent AF undergoing catheter ablation were included in the DECAAF II trial database. The primary endpoint of the study was the first confirmed recurrence of atrial arrhythmia. Recurrence was also monitored during the 90-day blanking period. A total of 287 patients experienced recurrent atrial arrhythmia during the blanking period, while 401 remained in sinus rhythm. Rates of longer-term arrhythmia recurrence were substantially higher among those who developed recurrence during the blanking period compared to those who remained in sinus rhythm throughout the blanking period (68% vs. 32%, P < 0.001). The study cohort was divided into three groups according to the timing of arrhythmia recurrence during the blanking period. Of those who had recurrent arrhythmia during the first month of the blanking period (Group 1), 43.9% experienced longer-term recurrence, compared to 61.6% who recurred during the second month of the blanking period (Group 2), and 93.3% of those who had arrhythmia recurrence during the third month (Group 3, P < 0.001). The risk of recurrent arrhythmia was highest in Group 3 (HR = 10.15), followed by Group 2 (HR = 2.35) and Group 1 (HR = 1.5). Receiver operating characteristic analysis was performed to assess the relationship between the timing of arrhythmia recurrence and the primary outcome (AUC = 0.746, P < 0.001). The optimal blanking period duration was identified as 34 days. Atrial fibrillation burden determined by smartphone electrocardiogram technology over the 18 months follow-up period was significantly higher in Group 3 (29%) compared to Groups 1 (6%) and 2 (7%) and in patients who stayed in sinus rhythm during the blanking period (5%) (P < 0.0001). CONCLUSION: Early atrial arrhythmia recurrence during the blanking period, particularly during the third month, is significantly associated with later recurrence. Although a blanking period is warranted, it should be abbreviated.

Catheter ablation improved ejection fraction in persistent AF patients: a DECAAF-II sub analysis.

AIMS: The aim of our study was to assess differences in post-ablation atrial fibrillation (AF) recurrence and burden and to quantify the change in LVEF across different congestive heart failure (CHF) subcategories of the DECAAF-II population. METHODS AND RESULTS: Differences in the primary outcome of AF recurrence between CHF and non-CHF groups was calculated. The same analysis was performed for the three subgroups of CHF and the non-CHF group. Differences in AF burden after the 3-month blanking period between CHF and non-CHF groups was calculated. Improvement in LVEF was calculated and compared across the three CHF groups. Improvement was also calculated across different fibrosis stages. There was no significant differences in AF recurrence and AF burden after catheter ablation between CHF and non-CHF patients and between different CHF subcategories. Patients with heart failure with reduced ejection fraction (HFrEF) experienced the greatest improvement in EF following catheter ablation (CA, 16.66% ± 11.98, P < 0.001) compared to heart failure with moderately reduced LVEF, and heart failure with preserved EF (10.74% ± 8.34 and 2.00 ± 8.34 respectively, P-value < 0.001). Moreover, improvement in LVEF was independent of the four stages of atrial fibrosis (7.71 vs. 9.53 vs. 5.72 vs. 15.88, from Stage I to Stage IV respectively, P = 0.115). CONCLUSION: Atrial fibrillation burden and recurrence after CA is similar between non-CHF and CHF patients, independent of the type of CHF. Of all CHF groups, those with HFrEF had the largest improvement in LVEF after CA. Moreover, the improvement in ventricular function seems to be independent of atrial fibrosis in patients with persistent AF.