Heart Rhythm

Background: Accurate identification of macro-reentrant atrial tachycardia (AT) circuits is critical for successful ablation but remains challenging with conventional mapping techniques. The aim of this study was to automatically detect macro-reentrant AT loops from high-density local activation time (LAT) maps. Methods: We developed an algorithm for automated detection of macro-reentrant AT circuits using LAT-derived directed graphs. Compared to previous graph-based approaches, the algorithm is designed to identify the fastest-conducting reentrant pathways and cluster them by rotational orientation (clockwise vs. counterclockwise) to distinguish single- from dual-loop circuits. The algorithm was applied retrospectively to 60 macro-reentrant scar-related AT cases mapped with CARTO or Ensite from two institutions. The results were compared with blinded expert electrophysiologist annotations of loop location and single- vs. dual-loop classification. Results: The 60 cases included 16 right atrial and 44 left atrial ATs from 51 patients. Expert review identified 57% single-loop and 43% dual-loop circuits. Compared with expert annotation, the algorithm correctly identified anatomical loop locations with 88% accuracy and correctly distinguished single- vs. dual-loop ATs in 93% of cases. Conclusion: Our LAT graph-based algorithm automatically identified single- and dual-loop macro-reentrant AT circuits. Localizing these pathways may provide insight into circuit mechanisms and help guide ablation.

PurposeObstructive sleep apnea (OSA) is a common comorbidity in heart failure (HF) patients with prevalence increasing as HF severity worsens. While CPAP/BiPAP has been shown to reduce disease burden and mortality in the general HF population, it is unclear whether these benefits extend to patients with left ventricular assist devices (LVADs). We sought to determine whether OSA affects long-term survival in newly implanted LVAD patients and whether CPAP/BiPAP treatment confers mortality benefits. MethodsThis single-center retrospective study included patients who underwent LVAD implantation between January 2007 and February 2022. Recipients were stratified by OSA status (OSA vs No-OSA), and those with OSA were further categorized based on CPAP/BiPAP compliance. Comparative statistics and Kaplan-Meier survival analyses were performed, with log-rank tests used to compare groups and assess survival differences. A Cox proportional hazards model was conducted to evaluate the association between risk factors and survival among patients with OSA and No-OSA. ResultsBefore LVAD implantation, patients with OSA had higher body mass index, hypertension, and a higher rate of implantable cardioverter-defibrillator placement than those without OSA. OSA was not associated with increased postoperative complications. Although survival did not differ significantly between OSA and No-OSA patients (p=0.33), CPAP/BiPAP-compliant OSA patients had significantly better survival than noncompliant patients (p=0.0099). ConclusionsLVAD patients with OSA who consistently use CPAP/BiPAP have better survival than those who do not. CPAP/BiPAP is a simple, low-risk treatment that can reduce mortality in this population. Therefore, increased perioperative screening for OSA should be considered for patients receiving LVADs. Multicenter studies are needed to confirm our findings further.

General anesthetics enable invasive experimentation but can affect cardiovascular and respiratory physiology, biasing preclinical outcomes. We compared five anesthetic regimens in adult male Wistar rats, tribromoethanol (TBE, 250 mg/kg i.p.), chloral hydrate (CH, 400 mg/kg i.p.), ketamine-xylazine (KX, 80/10 mg/kg i.p.), thiopental (TP, 80 mg/kg i.p.), and isoflurane (ISO, 4% induction, 2% maintenance), to investigate integrated cardiorespiratory and biochemical markers. Femoral arterial catheterization allowed continuous blood pressure (BP) and derived heart rate (HR) recordings, while ventilation was assessed through pletysmography at baseline (awake), during induction, and recovery phases of anesthesia. Variability was evaluated in the time and frequency domains, including HR, systolic blood pressure (SBP), and spontaneous baroreflex sensitivity. In an independent cohort of rats, butyrylcholinesterase (BChE), CK-MB, cTnI, and LDH were measured. Baseline BP was unchanged by TBE and TP, whereas all anesthetics affected HR. Minute ventilation and breathing frequency were reduced with all agents, while tidal volume decreased with KX and TBE only. LDH and cTnI were unaffected, BChE was reduced by KX, TBE, and ISO, and CK-MB increased with CH and KX. Variability analysis showed that all anesthetics depressed pulse-interval and SBP variability and shifted spectral power toward higher frequencies, while baroreflex sensitivity and effectiveness were consistently reduced. During recovery, KX and TP restored most variability indices, whereas CH, TBE, and ISO showed persistent suppression. These findings highlight distinct profiles of cardiovascular depression and biomarker responses across anesthetics and underscore the importance of accounting for autonomic variability when selecting different anesthetics in experimental protocols. HighlightsO_LIFive anesthetic regimens were tested in rats. C_LIO_LIAll anesthetics reduced ventilation, and KX and TBE also reduced tidal volume. C_LIO_LICH and KX increased CKMB, while KX, TBE and ISO reduced BChE. C_LIO_LIAll anesthetics reduced blood pressure variability and baroreflex sensitivity. C_LIO_LIVariability recovered with TP and KX, whereas CH, TBE and ISO showed persistent suppression. C_LI

AimsGenome-wide association studies have identified numerous cardiac transcription factors in association with atrial fibrillation. Amongst these transcription factors, the paired-like homeodomain transcription factor 2 (PITX2) is the strongest genetic risk variant associated with atrial fibrillation. However, the downstream mechanisms of PITX2 are not completely understood. Here, we explore the role of PITX2 in oxidative metabolism and stress as a unifying mechanism of arrhythmogenesis. Methods and resultsTo identify PITX2 mechanisms, we performed transcriptomic analysis in Pitx2c-deficient neonatal rat atrial myocytes. We identify oxidative phosphorylation as the top dysregulated pathway and direct transcriptional targets lie in mitochondrial electron transport chain complexes I and IV. Using the Seahorse Extracellular Flux Analyzer, we identified a functional decrease in oxidative metabolism in Pitx2c-deficient cardiomyocytes. As electron transport chain complexes I and IV may generate reactive oxygen species (ROS) under mitochondrial dysfunction, we quantified mitochondrial specific ROS using MitoSOX and observed an increase in mitochondrial specific ROS in Pitx2c-deficient cardiomyocytes. We additionally assessed spontaneous cardiomyocyte calcium cycling using Fluo-8AM and observed an increased frequency of pro-arrhythmogenic mechanisms including early and delayed afterdepolarizations as inferred through calcium traces. Further, we identified sarcomere disassembly including a potential role of PITX2 in regulating Titin, where Pitx2c-deficient cardiomyocytes display Titin mis-localization within the sarcomeres. To assess whether ROS drives these phenotypes, we treated neonatal rat atrial myocytes with N-acetylcysteine, a potent ROS scavenger, and observed decreased early and delayed afterdepolarizations, as well as restoration of Titin localization. ConclusionPITX2C maintains atrial metabolism and redox balance; the loss of PITX2C results in reduced oxidative metabolism and an elevation in oxidative stress that ramifies cardiomyocyte dysfunction. Treatment with antioxidant restores AF-associated phenotypes including abnormal calcium cycling and sarcomere disassembly in Pitx2c-deficient atrial cardiomyocytes. TRANSLATIONAL PERSPECTIVEGenetic variants close to the PITX2 gene associate most strongly with atrial fibrillation. This study reveals a mechanistic link between multiple AF-associated phenotypes and mitochondrial dysfunction with subsequent accumulation of reactive oxygen species downstream of PITX2. Importantly, metabolic therapies and reducing oxidative stress may present a potential clinical strategy to reverse and prevent functional and structural remodelling related to AF.

The recently published EHRA/EACVI consensus statement on a standardized bi-atrial regionalization provides new opportunities for consistent regional analyses across patients, imaging modalities and clinical centers. To make this standardized regionalization widely accessible, we developed the open-source software DIVAID, which automatically divides bi-atrial geometries according to the proposed regions, ensuring consistency, reproducibility and operator independence. We evaluated the accuracy of the algorithm by comparing its results to manual expert annotations across 140 geometries from multiple modalities and centers. Veins were automatically clipped correctly in 81% and orifices annotated correctly in 100% of cases. The median (interquartile range; IQR) Dice similarity coefficient (DSC) for left atrial regions was 0.98 (0.96-1.00) for DIVAID-expert and 0.98 (0.94-1.00) for inter-expert comparisons. For right atrial geometries, DSC was higher for DIVAID-expert than for inter-expert comparisons at 0.90 (0.80-0.95) and 0.88 (0.74-0.94), respectively. To assess the accuracy of regional boundaries, we computed the mean average surface distance (MASD) for boundaries derived from automatic or manual annotations. The median (IQR) MASD between DIVAID and experts was 0.17 mm (0.03-0.78) and 1.93 mm (0.65-3.96) in the left and right atrium, respectively. To conclude, DIVAID robustly divides anatomically diverse bi-atrial geometries according to the 15-segment model, while outperforming cardiac experts in both speed and consistency, and demonstrating an accuracy of regional boundaries comparable to the spatial resolution of cardiac imaging modalities. By providing automated, consistent atrial regionalization, DIVAID enables large-scale, standardized regional analyses and data-driven investigation of harmonized, multi-dimensional datasets, which may advance atrial arrhythmia research and personalized treatment strategies.

BackgroundSympathetic modulation via the stellate ganglia is increasingly recognized as a contributor to ventricular arrhythmogenesis after myocardial infarction. However, the mechanisms by which autonomic remodeling interacts with chronic infarct substrates to shape arrhythmic vulnerability remain incompletely understood. ObjectivesTo test the hypothesis that left- and right-sided stellate ganglion-mediated SNS modulation differentially reshapes ventricular arrhythmic vulnerability in chronic post-infarcted substrates, and that the RVI detects changes in vulnerability beyond conventional stimulation-based inducibility. MethodsFourteen patient-specific ventricular models with chronic post-infarcted remodeling were reconstructed from imaging data. A total of 336 simulations were performed under different combinations of stellate ganglion modulation, border zone remodeling, and fibroblast density. Arrhythmic vulnerability was quantified using 3D RVI mapping during paced rhythms and compared with conventional stimulation-based inducibility outcomes. ResultsStellate ganglion modulation induced marked, regionally heterogeneous changes in repolarization timing, resulting in lower and more negative RVI values in vulnerable regions. More negative RVI values reflect increased propensity for wavefront-waveback interaction and reentry initiation. Across the cohort, stellate modulation consistently decreased RVImin, even when inducibility outcomes remained unchanged. These findings indicate that SNS modulation can create a substrate more permissive to reentry independently of whether ventricular arrhythmia is triggered during programmed stimulation. ConclusionsStellate ganglion-mediated sympathetic modulation dynamically reshapes ventricular arrhythmic vulnerability in chronic post-infarcted substrates. RVI provides a spatially resolved, vulnerability-based metric that complements inducibility testing by revealing autonomic-substrate interactions underlying arrhythmogenesis Condensed AbstractSympathetic modulation via the stellate ganglia can alter ventricular repolarization and promote arrhythmogenesis after myocardial infarction, yet clinical responses remain heterogeneous. Using 14 patient-specific post-infarction ventricular models, we simulated left- and right-sided stellate modulation across combinations of border zone remodeling and fibrosis (336 simulations). Stellate modulation induced regionally heterogeneous repolarization shortening and reduced RVI values, even when programmed stimulation inducibility remained unchanged. These findings suggest that RVI captures substrate-level vulnerability beyond binary induction testing and may improve mechanistic assessment of autonomic-substrate interactions in chronic infarct substrates.

BACKGROUND: Observational studies have suggested an association between obstructive sleep apnea (OSA) and myocardial infarction (MI), but whether this relationship is causal or largely reflects shared risk factors remains unclear. METHODS AND RESULTS: We performed a 2-sample Mendelian randomization (MR) analysis to evaluate the causal effect of OSA on MI. Summary statistics for OSA were obtained from FinnGen, and MI data were obtained from the UK Biobank, with external validation using CARDIoGRAMplusC4D. Mediation MR was used to assess 13 potential mediators, and a 6-step multivariable MR framework was applied to estimate the direct effect of OSA after sequential adjustment for potential confounders. Reverse MR was conducted to test possible reverse causality. Genetically predicted OSA liability was associated with increased MI risk (odds ratio [OR] per log-OR increase, 1.0024 [95% CI, 1.0010-1.0039]; P=0.001). Body mass index (BMI) was the strongest mediator, explaining 35.94% of the association (P=0.030), whereas systolic blood pressure (SBP) showed minimal mediation (0.28%; P=0.678). In stepwise multivariable MR, the OSA-MI association was attenuated after adjustment for BMI and SBP (P=0.156), suggesting partial confounding by shared cardiometabolic risk. In a model including SBP and atrial fibrillation (AF), AF remained independently associated with MI (P=0.004), whereas OSA showed only a marginal direct effect (P=0.050). Reverse MR found no evidence that MI influenced OSA risk. CONCLUSIONS: These findings support a causal association between OSA and MI and suggest that this relationship may be mediated in part through obesity-related and arrhythmia-related pathways. AF may represent an important intermediate component of OSA-related cardiovascular risk beyond traditional hemodynamic factors. Keywords: obstructive sleep apnea; myocardial infarction; Mendelian randomization; mediation analysis; obesity.

Background: Clinical genetic evaluation for patients with dilated cardiomyopathy (DCM) is minimally implemented and models of care are not defined. To understand current genetics care for DCM, a systematic needs assessment was conducted. Methods: Principal Investigators (PIs) of the DCM Consortium convened at the Summer Scientific Symposium in July 2025. An electronic needs assessment was collected from the 24 PIs in advance to define current care models by evaluating which Heart Failure Society of America-recommended genetic evaluation components are conducted, by whom, and time required. Descriptive statistics were generated to characterize model features. Focus group discussions explored barriers and facilitators to implementing genetic services. Results: Four care models emerged from the PI responses: 1 -- Traditional-Synchronous (25%, n=6, requiring the most time per patient), 2 -- Traditional-Asynchronous (33%, n=8), 3 -- Externally Sourced (17%, n=4), and 4 -- Physician/Advanced Practice Provider Conducted (25%, n=6, requiring the least time per patient). All models used genetic testing, whereas other components were implemented variably or not at all. Models 1 (15.7{+/-}4.1) and 2 (15.4{+/-}3.0) were rated more acceptable than Model 4 (9.8{+/-}2.9, 1 vs 4: p=0.027; 2 vs 4, p=0.023). Notably, 88% of PIs used genetic information for treatment decisions, including ICD placement (83%; n=20) or cardiac transplant (63%; n=15). Major facilitator themes from focus group discussions included having a genetic counselor on the HF team and developing authoritative standards directing provision of DCM genetic services. Barrier themes included operational challenges, limited personnel, clinician under-recognition, need for new service delivery models, and billing/reimbursement. Conclusions: DCM genetic care models and components were highly variable across the 24 sites of the DCM Consortium, even though all sites discussed similar factors that enable or hinder implementing genetic services for DCM. Understanding the basis of practice model variability may provide insight to yield more scalable care approaches.

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia worldwide and is strongly associated with increased risks of stroke, heart failure, and mortality. Traditional methods to predict AF and prognostic its associated risks often fail to capture the full complexity of AF patterns, limiting their predictive accuracy. In spite of the improvements achieved by machine learning (ML) techniques, state-of-the-art AF-focused predictors do not generally incorporate longitudinal data, reducing their capacity to model the dynamic and evolving nature of individual behaviors and physiological indicators over time. The absence of a longitudinal perspective restricts understanding of how AF risk develops and changes across prognostic windows. This study addresses these limitations by developing superior ML models tailored to predict adverse events within a longitudinal Portuguese cohort of individuals with AF. The work targets six clinical endpoints: stroke, all-cause death, cardiovascular death, heart failure hospitalizations, inpatient visits, and acute coronary syndrome. The predictors yielded an AUC of 0.65 for 1-year stroke prediction, outperforming CHA2DS_2-VASc (0.59). For all-cause mortality prediction, the models achieved an AUC of 0.78 against the 0.72 reference of GARFIELD-AF. In addition to predictive advances, the study identifies determinants of AF-related risks and introduces a prototype decision-support tool for clinical use.

Background Exercise capacity varies among individuals with a Fontan circulation. Percent predicted peak oxygen consumption (%pVO2) may be influenced by ventricular morphology, Fontan subtype, and conduit characteristics, but data explaining variability in exercise capacity are limited. This study examined whether anatomical and surgical factors are associated with %pVO2 later in life. Methods Participants enrolled in the multicenter Single Ventricle Outcomes Network (SV-ONE) database who had cardiopulmonary exercise testing (CPET) data were included. Published reference equations were used to estimate %pVO2. Multivariable regression models evaluated associations between anthropometric, anatomical (diagnosis and dominant ventricle), and surgical (Fontan subtype, conduit size, and surgical era) factors and %pVO2. Restricted spline analyses assessed nonlinearity. Results 561 individuals with a Fontan circulation were included in the analysis; age 20 {+/-} 8 years, 54% male, mean %pVO2 was 63 {+/-} 16%. Sex and exercise modality were the strongest predictors of %pVO2, with females being 12% higher than males and treadmill 4.6% higher than a cycle. Age at CPET was a predictor of exercise capacity with %pVO2 decreasing by 0.8% per year. Ventricular morphology, diagnosis, and Fontan subtype did not have a statistical association with the primary outcome. In models restricted to patients with an extracardiac conduit (n = 330), conduit diameter and area were not associated with %pVO2, even after indexing to body surface area. Univariable nonlinear spline analyses suggested an optimal conduit size of 18 mm for %pVO2, but this was not significant after body size adjustments. Conclusion In this large multicenter cohort, surgical and anatomical features were not as important as sex, age, and body size as determinants of exercise performance in patients with a Fontan circulation. Reduced exercise capacity in this population appears to reflect progressive pathophysiological changes of the Fontan circulation rather than specific characteristics such as conduit size, ventricular morphology, or anatomy.

BackgroundVentricular assist devices (VADs) are used as treatment for end-stage heart failure in children and adults. We previously demonstrated decreased mitochondrial function and changes in cardiolipin, a mitochondrial phospholipid, in explanted pediatric and adult failing hearts. In this study, we tested the hypothesis that VAD unloading of failing hearts leads to positive changes in myocardial cardiolipin in both pediatric and adult hearts. MethodsVentricular tissue was collected from the same patient at time of VAD implantation and at transplant. Ejection fraction (EF), left ventricular internal diameter at end-diastole (LVIDd) and brain natriuretic peptide (BNP) were assessed pre- and post-VAD. Cardiolipin species from paired VAD core and explants were quantified using liquid chromatography mass spectrometry. Mitochondrial respiration was measured in ventricular tissue pre- and post-VAD in paired pediatric samples using the Oroboros Oxygraph-2k. ResultsVAD support led to increased EF and decreased LVIDd and BNP. The predominant cardiolipin species in cardiac mitochondria, tetralinoleoylcardiolipin, was positively remodeled in pediatric post-VAD myocardium, while adult post-VAD myocardium demonstrated significantly increased total cardiolipin and decreased oxidized cardiolipin but did not demonstrate the tetralinoleoylcardiolipin remodeling seen in pediatric hearts. In pediatric patients, VAD support resulted in significant increases in Complex I+II activity, and a trend toward increases in Complex I activity. ConclusionOur data demonstrate age-related differences in VAD-associated cardiolipin remodeling and suggest that improved mitochondrial function in pediatric VAD-supported hearts could be related to increased tetralinoleoylcardiolipin.

BACKGROUNDSubcutaneous white adipose tissue (scWAT), a key metabolic and endocrine organ, is inevitably exposed during radiotherapy (RT). While RT is a cornerstone of cancer treatment, its efficacy is limited by toxicity to surrounding healthy tissues. Ultra-high dose rate (FLASH) RT has emerged as a promising modality capable of preserving tumor control while reducing normal tissue damage - the so-called FLASH effect. Clinical evidence indicates that childhood exposure to conventional (CONV) RT is associated with long-term dysmetabolism and WAT dysfunction. However, the impact of FLASH-RT on WAT has not been investigated. AIMTo compare the effects of FLASH- and CONV-RT on adipocyte function and scWAT homeostasis, and to identify molecular and structural changes associated with each modality. METHODSWe evaluated the effects of FLASH- and CONV-RT on adipocytes and scWAT using a dedicated linear accelerator capable of delivering both modalities. Experiments were performed in the human SGBS preadipocyte/adipocyte cell line and in a mouse model subjected to proximal hind limb irradiation, with analyses conducted 70 days post-exposure. RESULTSRT impaired adipogenic differentiation in a dose-dependent manner, with a relative sparing effect of FLASH at 4-8 Gy. Mature adipocytes exhibited radioresistance, with protection by FLASH at 8 Gy. In vivo, both regimens reduced fat mass without affecting body weight, with greater loss following CONV-RT. Transcriptomic profiling of scWAT revealed inflammatory and neurodegenerative signatures after CONV-RT, whereas FLASH-RT induced minimal transcriptional changes. Histological and ultrastructural analyses confirmed increased cellular damage, vacuolization, lipid spill-over, and reduced PLIN1 expression, predominantly in CONV-treated mice. CONCLUSIONSWAT homeostasis is sensitive to conventional RT, whereas FLASH-RT better preserves tissue structure and function, with implications for long-term metabolic health in cancer survivors.

Background: Detection of disease progression is key to personalize treatment strategies in transthyretin cardiomyopathy (ATTR-CM), particularly with emerging therapies. Echocardiography can detect subtle longitudinal changes but is limited by operator dependence. This study evaluates agreement and reproducibility of fully automated, AI-assisted echocardiographic measurements under real-world conditions. Methods: This retrospective study included 62 patients with ATTR-CM undergoing 178 serial annual echocardiograms assessed by a reference cardiologist, a second cardiologist, a novice reader, and a fully automated AI algorithm (Us2.ai). Interrater agreement was assessed using Bland-Altman analysis and intraclass correlation coefficients (ICCs). Intrarater variability for human readers was derived from repeated blinded measurements, with limits of agreement (LoA = mean difference +/- 1.96 x SD) defining the smallest detectable change. AI repeatability was assessed using within-study pairwise differences. Results: AI showed moderate agreement with the reference cardiologist for IVSd and LVEDV (ICC 0.65 and 0.51), with biases of -1.9 mm and -39 mL, respectively. Interrater agreement between cardiologists was good (ICC 0.79 and 0.84) with minimal bias (-0.2 mm and +3 mL). Intrarater variability was moderate to excellent for both cardiologists (LoA 3.0 mm and 43 mL for the reference cardiologist; 2.7 mm and 31 mL for the second cardiologist). AI demonstrated comparable repeatability (LoA 3.6 mm and 37 mL), while the novice showed higher variability (5.1 mm and 61 mL). Conclusion: AI-based measurements demonstrated repeatability comparable to experienced cardiologists. Despite moderate agreement and systematic differences in volumetric assessments, their reproducibility supports automated analysis for longitudinal echocardiographic monitoring.

This protocol describes a Langendorff-based method for isolating intact adult mouse ventricular myocytes using syringe pump-driven perfusion. The approach retains the key physiological advantage of the conventional Langendorff technique, continuous retrograde coronary perfusion, while simplifying the overall setup. By combining retrograde aortic perfusion with widely available laboratory equipment, the method provides an accessible alternative to traditional Langendorff systems. A precision syringe pump connected to an in-line heater is used to deliver temperature-controlled, constant-flow perfusion during enzymatic digestion. In contrast to gravity-driven constant-pressure systems, constant-flow perfusion maintains stable enzyme delivery despite changes in coronary resistance that occur during tissue digestion. Use of an inline heater allows precise, rapid temperature-controlled delivery, avoiding the complexity, leak risk, thermal lag, and contamination susceptibility associated with traditional water-jacketed systems. Our setup reduces variability in perfusion rate and minimizes susceptibility to occlusion, flow interruption, or compliance-related artifacts, enhancing reproducibility. The method consistently yields adult ventricular myocytes with high viability (>70% rod-shaped, calcium-tolerant), enabling a broad range of functional analyses including electrophysiology, contractile performance and calcium handling. Step-by-step instructions, troubleshooting guidance, and anticipated outcomes are provided to facilitate adoption in laboratories without dedicated isolated-heart perfusion infrastructure. Key FeaturesO_LISimplified Langendorff-based mouse cardiomyocyte isolation method that eliminates the need for specialized perfusion rigs. C_LIO_LISyringe pump-driven constant-flow perfusion combined with inline temperature control improves reproducibility by ensuring stable enzyme delivery and precise temperature regulation. C_LIO_LIGenerates high-yield, calcium-tolerant adult mouse ventricular myocytes suitable for functional studies. C_LI Graphical Overview O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=190 SRC="FIGDIR/small/718810v1_ufig1.gif" ALT="Figure 1"> View larger version (63K): org.highwire.dtl.DTLVardef@18cabc6org.highwire.dtl.DTLVardef@61831eorg.highwire.dtl.DTLVardef@1e76036org.highwire.dtl.DTLVardef@15d8268_HPS_FORMAT_FIGEXP M_FIG Graphical overview of the simplified Langendorff-based mouse cardiac myocyte isolation protocol. C_FIG

Structured AbstractO_ST_ABSBackgroundC_ST_ABSAtrial fibrillation (AF) is maintained by complex dynamics, clinically characterised by bursting periods of organization and disorganization in intracardiac electrograms. We have previously postulated that cardiac conduction behaves like a critical system, where phase shift from organised rhythm to AF is a phase transition at the critical point. We thus hypothesized that using multifractal analysis of AF electrograms could potentially quantify non-stationary fluctuations, revealing novel mechanistic insights into the cardiac critical system and examine potential clinically relevant markers of AF dynamics, phenotype and treatment response. ObjectivesTo determine whether multifractal analysis of AF electrograms can (i) Distinguish paroxysmal (PAF0 and non-paroxysmal AF (NPAF), (ii) predict response to pharmacologic modulation, and (iii) identify imminent spontaneous termination, thereby acting as marker of proximity to criticality along complex system phase spectrum. MethodsWe analysed >1.4 million seconds of high-density bipolar electrograms from 106 patients (paroxysmal n{approx}52, non-paroxysmal n{approx}54) undergoing left atrial mapping with a 24-bipole HD-Grid catheter at standardized sites (RENEWAL AF-ANZCTR ACTRN12619001172190)). Multifractal analysis using the Wavelet Transform Modulus Maxima Method (WTMM) was applied to a burst-energy observable to derive log-normal multifractal parameters c (support dimension), c (spectrum location), and c2 (fluctuations). Hierarchical mixed-effects models accounted for channels nested within locations within patients. A flecainide sub-study (n=15) provided paired pre-/post-infusion recordings, and 27 spontaneous termination events in 15 patients were analysed using 60-s pre-termination windows. Spatial texture of c2 was quantified by variogram-derived correlation length and sill. ResultsAF electrograms exhibited robust multifractality confirming multifractal fluctuations as an intrinsic property of AF. Non-paroxysmal AF showed significantly reduced fluctuations versus paroxysmal AF (c2: {beta}=-0.01, p=0.001), indicating a paradoxical loss of fluctuations with disease progression. Flecainide selectively increased fluctuations in paroxysmal AF ({Delta}c2 = +0.04, p<0.01; {Delta}c = +0.06, p<0.01) but had no significant effect on fluctuations (c2) in non-paroxysmal AF, revealing phenotype-dependent drug response. Immediately prior to spontaneous AF termination, fluctuations increased significantly compared with sustained AF (c2: 0.198 vs 0.181, p=0.024). Spatial variogram analysis revealed heterogenous patterns in paroxysmal AF, whereas non-paroxysmal AF displayed a homogenised, flattened fluctuations landscape. ConclusionsAtrial fibrillation exhibits robust multifractal dynamics rather than random electrical activity. Reduced fluctuations characterizes non-paroxysmal AF, whereas higher fluctuations is observed in paroxysmal AF, during flecainide modulation, and immediately prior to spontaneous termination. These findings suggest that multifractal fluctuations (c2) reflects the dynamical state of AF and may serve as a quantitative biomarker of disease progression, pharmacologic responsiveness, and proximity to termination. CONDENSED ABSTRACTTAtrial fibrillation (AF) exhibits multifractal electrogram fluctuations that vary with disease stage, pharmacologic responsiveness, and proximity to spontaneous termination. In this study, multifractal fluctuations (c2) was higher in paroxysmal than non-paroxysmal AF, increased selectively with flecainide in paroxysmal AF, and rose immediately before spontaneous termination. These findings identify c2 as a quantitative marker of AF progression, and imminent reorganization. Clinically, multifractal analysis may enhance intra-procedural assessment of AF phenotype, guide drug selection, and improve recognition of transitions toward sinus rhythm, and connects AF with concepts of criticality and phase transitions.

Abstract Background: ST-elevation myocardial infarction (STEMI) is reported to be a leading cause of mortality worldwide. While cardiac troponins are the gold standard for myocardial injury detection but creatine kinase-MB (CK-MB) and total creatine phosphokinase (CPK) retain prognostic use in resource-limited settings. Objective: To evaluate the prognostic significance of admission CK-MB and CPK levels in STEMI patients and to assess their association with hematological parameters for integrated risk stratification. Methods: This cross-sectional study enrolled 15 consecutive STEMI patients from the Punjab Institute of Cardiology, Lahore, during January 2024. Comprehensive laboratory analysis including cardiac biomarkers (CK-MB, CPK, troponin-I, LDH), complete blood count, renal function, serum electrolytes, and metabolic parameters, was performed on admission. Pearson correlation and comparative statistical analyses were also conducted to assess the relationships between cardiac biomarkers and hematological indices. Results: The cohort includes 15 patients (mean age 50.1 +/- 12.2 years; 73.3% male). Cardiac biomarker elevation was prevalent: CK-MB was elevated in 12/15 (80%), CPK was elevated in 12/15 (80%), with concordant elevation in 11/15 (73.3%), which indicates extensive myocardial necrosis. Troponin-I showed the highest elevation rate at 13/15 (86.7%). Hematological abnormalities included anemia (60%), WBC elevation (53.3%), and RBC reduction (40%). Random glucose averaged 150.80 +/- 63.55 mg/dL, with 66.7% highlighted the hyperglycemia. Remarkably, electrolyte balance was preserved in all of the patients (0% sodium, potassium, and bicarbonate abnormalities), indicating maintained homeostasis. Pearson correlation analysis revealed a significant correlation between CK-MB and CPK (r = 0.615, p = 0.0126), while correlations between cardiac biomarkers and hematological parameters were weak (p > 0.05). Risk stratification identified 53.3% of patients as high-risk who required intensive management. Conclusions: CK-MB and CPK demonstrate significant concordance and retain prognostic value in STEMI patients, particularly in resource-limited settings where troponin access may be constrained. While troponin-I remains the most sensitive biomarker, combined assessment of conventional cardiac enzymes supports reliable evaluation of myocardial injury. Hematological parameters reflect systemic response but show limited correlation with cardiac biomarkers.

Background: Deep brain stimulation (DBS) is a treatment option for Parkinson disease (PD). However, the effect of DBS on the arterial pressure (AP) remains unexplored. We aimed to develop an artificial baroreflex system for treating orthostatic hypotension (OH) due to central baroreflex failure in patients with PD. To achieve this, we developed an appropriate algorithm after estimating the dynamic responses of the AP to DBS using a white noise system identification method. Methods: We randomly performed DBS while measuring the AP tonometrically in 3 trials involving 3 patients with PD treated with DBS. We calculated the frequency response of the AP to the DBS using a fast Fourier transform algorithm. Finally, the feedback correction factors were determined via numerical simulation. Results: The frequency responses of the systolic AP to random DBS were identifiable in all 3 trials, and the steady state gain was 8.24 mmHg/STM. Based on these results, the proportional correction factor was set to 0.12, and the integral correction factor was set to 0.018. The computer simulation revealed that the system could quickly and effectively attenuate a sudden AP drop induced by external disturbances such as head-up tilting. Conclusion: An artificial baroreflex system with DBS may be a novel therapeutic approach for OH caused by central baroreflex failure.

Background: Mainstreaming genetic testing has emerged as a strategy to improve access and reduce wait times for patients who may benefit from genetic testing. Ensuring patients fully grasp the implications of testing when formal genetic counselling is not provided, remains a focus for ongoing research. Methods: Patients diagnosed with hypertrophic or dilated cardiomyopathy were offered genetic testing between September 2024 and September 2025 through either the mainstreaming model conducted in cardiology clinics or a referral to Medical Genetics where patients attended an online webinar or a one-on-one genetic counselling appointment. Uptake of testing, time to testing, informed choice and patient satisfaction were evaluated. Results: Among patients offered genetic testing, uptake was higher in the mainstreaming pathway (82%) compared with a referral to Medical Genetics (69%). The difference in access was predominately due to patients not following through with their Genetics referral. Mainstreaming reduced wait times where patients referred to Genetics waited a median of 94-185 additional days to be offered genetic testing. Despite improved access, only 62% of mainstreamed patients were considered informed, compared to 91% of patients that attended a patient webinar through Medical Genetics (p < 0.01). Satisfaction with decision-making was high across both pathways. Conclusion: Integrating genetic testing into cardiology practices increased access and reduced wait times; however, patients demonstrated significantly lower rates of informed decision making compared to those who attended a patient webinar offered through Medical Genetics. These findings highlight the importance of structured education to support informed decision making within mainstreaming pathways.

Aims: Responses to remote pulmonary artery pressure data vary across programs. We evaluated SMART-HF, a structured pulmonary artery diastolic pressure (PAD)-guided workflow, in a community heart failure cohort. Methods: We retrospectively analysed adults with heart failure and an implanted pulmonary artery pressure sensor managed with SMART-HF. Pulmonary artery diastolic pressure (PAD) was calculated from prespecified 14-day windows at baseline, 90 days, and 6 months. Two hemodynamic management performance indices (HMPI) were prespecified: the 6-Month Delta HMPI (PAD reduction >2 mmHg from baseline) and the 90-Day Target HMPI (PAD [&le;]20 mmHg at 90 days). Exploratory analyses evaluated patients with baseline PAD >20 mmHg. Results: Of 37 patients, 36 had paired 90-day and 29 had paired 6-month windows. Mean PAD decreased from 18.3 +/- 7.0 to 16.1 +/- 6.3 mmHg at 90 days and from 18.8 +/- 6.8 to 15.5 +/- 5.8 mmHg at 6 months (both P < 0.001). The 90-Day Target HMPI was achieved in 26/36 (72.2%) and the 6-Month Delta HMPI in 19/29 (65.5%) [95% CI 45.7-82.1]. In the exploratory subgroup (baseline PAD >20 mmHg), mean PAD changes were -2.9 +/- 3.6 mmHg at 90 days (n = 19; P = 0.002) and -4.9 +/- 4.9 mmHg at 6 months (n = 15; P = 0.002). Conclusions: SMART-HF was associated with improved ambulatory pulmonary artery diastolic pressure control at 90 days and 6 months. Exploratory subgroup findings support further evaluation in patients with elevated baseline pulmonary artery diastolic pressure.

Abstract: Background: Vascular access is essential in treating patients undergoing prolonged endovenous therapy such as chemotherapy, antibiotics, and parenteral nutrition. Since the 1990s, when PICCs (peripherally inserted central catheters) appeared, vascular access options have expanded significantly, revolutionizing the treatment landscape for all types of patients. Objective: To analyze and describe the profile of the use of PICCs in a Brazilian quaternary hospital over 10 years with data collected by the infusion therapy team. Evaluating the number of PICCs implanted over the years, patients epidemiology and clinical characteristics, insertion details, associated complications, and the reason for removal. Methods: A retrospective cohort study that employs a quantitative, non-experimental approach to classify and statistically analyze past events associated with 21,652 PICCs implanted from January 2012 to December 2021 in a quaternary hospital at Sao Paulo - Brazil. All the catheters were implanted, and the data was collected by a team of nurses specializing in infusion therapy. We analyzed the number of catheters implanted over the years, insertion characteristics, patients epidemiology and clinical data, possible associated complications, and the reason for removal. Statistical analyses were conducted using R software (version 4.4.1) and SPSS (version 29) for Windows (IBM Corp, Armonk, NY). Results: During the specified period, 21,652 catheters were analyzed. The patients gender distribution was nearly balanced (48.2% versus 51.8%), and the average age was 66 years. Cardiovascular and metabolic issues were the most common comorbidities, and between 2020 and 2021, 29.3% of the sample tested positive for COVID-19. The most common location of hospitalization and implantation was the medical-surgical clinic (31.6% - 41.4%), and the most used type of catheter was the Power Picc (83.9%). The estimated complication incidence density is 2.94 complications per 1,000 catheter-days. Almost all the PICCs (98,2%) were adequately located at the cavo-atrial junction after the first attempt, 82.2% of catheters were removed after therapy, and the median duration of catheter use was 12 days. Conclusion: PICCs are widely employed for drug infusion, with their use growing progressively due to specialized teams greater availability and training. The high efficiency of these devices with a relatively low risk of complications already observed in previous studies was reinforced by the findings of this study of more than 20,000 catheters.