Heart Rhythm

Background: Congenital junctional ectopic tachycardia (cJET) is a rare, potentially life-threatening arrhythmia suspicious for a genetic basis, yet its molecular underpinnings remain incompletely defined. The POPDC2 gene, involved in cardiac pacemaking and membrane trafficking of interacting ion channels, has not previously been conclusively linked to human tachyarrhythmias. This study investigates a novel POPDC2 variant (p.Leu245Pro) identified in a family with autosomal dominant cJET. Methods: Exome sequencing was performed to identify co-segregating variants in the affected family. Functional analysis of the POPDC2 p.Leu245Pro variant was conducted by molecular dynamics (MD) simulations, a membrane targeting assay, and a bimolecular fluorescence complementation assay. Additionally, the impact of the variant on Nav1.5 and TREK-1 currents was characterized in Xenopus oocytes. Results: The p.Leu245Pro POPDC2 variant showed a destabilization of the POPDC1-POPDC2 dimer interface, resulting in impaired heterodimer formation and membrane localization. Electrophysiological studies in Xenopus oocytes demonstrated that the mutant protein significantly affected Nav1.5 and TREK-1 currents. These findings support a functional impact of the POPDC2 p.Leu245Pro variant relevant to cardiac conduction. Conclusions: Our results provide the first functional evidence implicating POPDC2 in cJET and support its role as a novel candidate gene in tachyarrhythmic disease. This study enhances the understanding of genetic contributions to cJET and suggests further investigation of POPDC2 in other forms of supraventricular tachyarrhythmias.

Background: Patients with Fontan circulation experience significant morbidity from supraventricular tachyarrhythmias (SVTs). However, the electrophysiological features of SVT and the efficacy and safety of catheter ablation in patients with Fontan circulation are poorly understood. This study aimed to elucidate the electrophysiological features of SVT and evaluate the efficacy and safety of catheter ablation in patients with Fontan circulation. Methods: Forty-nine patients (age, 29.2{+/-}10.0 years; 27 males) with functional single ventricle and Fontan circulation who had undergone electrophysiological study for SVT were retrospectively enrolled. Parameters analyzed included underlying congenital heart disease, Fontan type, conduit puncture technique, tachycardia mechanisms, tachycardia origin site, acute success rate, procedure-related complications, and recurrence. Results: Fifty-nine SVTs were induced, and 69 catheter ablations were performed. The Fontan types included atriopulmonary connection (APC, 18.4%), lateral tunnel (LT, 38.8%), and extracardiac conduit (ECC, 42.9%). Inducible tachycardias included intra-atrial reentrant tachycardia (IART, 39.0%), focal atrial tachycardia (AT, 28.8%), atrioventricular reentrant tachycardia (11.9%), atrioventricular nodal reentrant tachycardia (10.2%), and atrioventricular reciprocating tachycardia involving the twin atrioventricular nodes (10.2%). The right atrial (RA) lateral wall was the most common location of IART and focal AT. The acute success and complication rates were 73.5% and 4.1%, respectively. Recurrence rate was 34.7% during follow-up of 78.0{+/-}71.9 months. The cumulative recurrence rate was significantly lower in patients who underwent LT or ECC Fontan procedures than in those who underwent the APC Fontan procedure (P<0.001). Conclusions: Catheter ablation for SVT is effective and safe in patients who have undergone LT and ECC Fontan procedures.

BACKGROUNDIn addition to lethal ventricular arrhythmias, arrhythmogenic cardiomyopathy (ACM) is associated with conduction abnormalities, bradycardias, and reduced expression of the scaffolding junctional protein zonula occludens-1 (ZO-1). Reduced ZO-1 expression is also seen in dilated cardiomyopathy, which is far more common than ACM. Conduction abnormalities are likewise a feature of ZO-1 cardiac-specific knockout (ZO-1cKO) mice. However, the role of ZO-1 in sinoatrial node (SAN) automaticity has not been studied. OBJECTIVETo investigate the role of ZO-1 in SAN automaticity and elucidate the mechanisms by which ZO-1 deficiency leads to SAN dysfunction. METHODSZO-1 cardiac-specific knockout (ZO-1cKO) mice were generated by crossing ZO-1 floxed mice with MHC-nuclear Cre mice. SAN/atrial tissue and isolated SAN cells were examined using optical mapping, single-cell patch clamp, and quantitative PCR techniques to assess functional alterations caused by ZO-1 loss. RESULTSZO-1cKO mice exhibited enlarged atria and SAN area compared to control mice, with normal left ventricular function. Electrocardiograms showed sinus bradycardia, sinus pauses and atrioventricular block. Optical mapping revealed a caudal shift in the SAN leading region and reduced intra-atrial conduction velocity in ZO-1cKO mice. Patch-clamp recordings from isolated SAN cells showed reduced spontaneous action potential frequency and diastolic depolarization rate, while voltage-clamp revealed a marked reduction in pacemaker current (If). CONCLUSIONZO-1 expression is essential for SAN automaticity. Its loss impairs SAN impulse generation by reducing pacemaker current and hampering atrial conduction, leading to bradyarrhythmia, conduction delay and block. These findings help explain impulse generation and conduction abnormalities in ACM and other cardiomyopathies.

BackgroundRemote monitoring (RM) enables convenient follow-up of patients with cardiac implantable electronic devices. In remote-only monitoring (RM-only) in-person visits are only scheduled if needed based on RM findings. This study evaluated the feasibility and safety of long-term RM-only of pacemaker (PM) patients. MethodsAll patients with Biotronik PM were included in the analysis. Data on the number and causes of additional in-office device interrogations, actions due to the transmissions, hospitalizations and performance of RM were collected from a large cohort of pacemaker patients followed by RM-only. ResultsIn total 606 patients (302 female) with mean age of 78{+/-}12 years were included in the analysis. During the mean follow-up of 2.8 years 445 additional in-office device interrogations were made in 287 patients (0.3 interrogations / year), and in 110 (25%) of these cases changes to device programming were made. In a subgroup analysis of 100 patients with at least one year of prior appointment-based device monitoring, the need for in-office visits was 6.9 times higher per follow-up year than in RM (IRR=6.9, 95% CI 4.9-9.9; p<0.001). The hospitalization rate in the entire cohort during RM was 0.3 / year with no difference in the rate of hospitalizations between the two monitoring methods (IRR 1, 95% CI 0.8-1.4, p=0.8). The success of daily transmissions was 91.7 %. ConclusionOur real-word data indicate that RM-only offers an efficient and safe method for long-term follow-up of pacemaker patients.

Background and Aims: Clinical interpretation of the precordial leads V1-V6 assumes that Wilson's central terminal (WCT) has a fixed anatomical location. Consequently, a positive signal corresponds to electrical activation spreading from WCT towards the respective electrode, and vice versa. However, the location of WCT has never been systematically investigated. Yet, a better understanding of WCT location could improve the interpretation of the precordial leads. This work aims to characterize the spatial expansion and location of the physical WCT i.e., the electrical potential defined by the WCT, during the P-wave on the body surface. Methods: An intensive analysis of body surface potential maps (BSPMs) during atrial depolarization in an in silico patient cohort and clinical data was conducted. Results: During the P-wave, the location of WCT was not stationary but the spatial extent and location varied across time as well as across individuals. Four distinct spatial patterns of WCT distribution on the body surface were identified in silico, and three of these were found in the clinical cohort. WCT signals agreed with BSPM signals at commonly assumed positions of WCT only for a small fraction of the P-wave. Conclusion: The spatial extension and location of WCT changes during the P-wave and thus should be considered when interpreting the precordial leads.

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.

Background Pulse-field ablation (PFA) is regarded as a non-thermal ablation modality, but there is an increasing range of complications that could be due to thermal effects. Methods The hydrogel undergoes permanent colour change when a target temperature is reached allowing direct visualisation of the surface thermal footprint and depth. Comparative lesion sets using a variable loop circular catheter (VP), circular over-the-wire catheter (PS) and pentaspline catheter (FP) were performed. Protocols included single and stacked applications with variation of force, irrigation, and voltage. The hydrogel lesions were analysed en-face and by section using digital image analysis. Results All 3 PFA catheters tested had significant thermal footprints. The VP catheter had the largest mean surface footprint (156.1mm2) and thermal depth (1.31mm) compared to the other two catheters (PS 55.4mm2 & 1.1mm, FP 29.8mm2 & 1.05mm, p<0.005). Increasing irrigation showed a trend to reduce thermal footprint but did not achieve statistical significance. Increasing voltage increased thermal footprint, but increasing force had negligible effect. Stacked lesions incrementally increased thermal lesion footprint and depth in all catheters. Thermal depths of up to 2.4mm were observed. Areas of darkening and degradation of the hydrogel were observed with the VP and FP catheters, consisting of up to 47% of lesion area. No darkening was observed with the PS catheter. Conclusions There are significant thermal footprints in all the systems tested. Temperatures exceeding 60oC have been demonstrated, comparable to radiofrequency ablation, and this may explain the mechanism of injury in some reports of collateral damage during PFA.

Background: Response to cardiac resynchronization therapy (CRT) is heterogeneous in patients with non-left bundle branch block (non-LBBB) heart failure. Whether pre-implant substrate or procedural characteristics provide the more stable framework for predicting 1-year echocardiographic response remains uncertain. Methods: We retrospectively analyzed 120 non-LBBB patients undergoing CRT. The primary logistic model included left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left atrial diameter, log-transformed NT-proBNP, baseline QRS duration, fragmented QRS burden across V1?V6 leads, and pulmonary artery pressure. Missing predictor data were handled using multiple imputation with 20 datasets. Model performance was assessed using bootstrap internal validation and recalibration. A prespecified procedural extension added pacing strategy, posterolateral biventricular left ventricular lead location, left ventricular pacing threshold, and right ventricular lead position. Exploratory phenotyping and sensitivity analyses were performed. Results: Echocardiographic response occurred in 51 patients (42.5%). LVEDD (OR, 0.899 [95% CI, 0.826?0.978]; P=0.013) and LVEF (OR, 1.068 [95% CI, 1.000?1.140]; P=0.050) were the most informative predictors. The primary model showed apparent AUC 0.811 and Brier score 0.173, with optimism-corrected AUC 0.766 and calibration slope 0.765. Procedural extension showed no retained incremental value after validation. Exploratory phenotyping identified three response patterns with moderate stability. Conclusions: In non-LBBB CRT, baseline structural, biomarker, and electrocardiographic substrate provided the most stable framework for predicting 1-year echocardiographic response. Procedural variables added limited retained value, suggesting that pacing strategy should be interpreted alongside baseline substrate.

Background: Concomitant arrhythmogenic right ventricular cardiomyopathy (ARVC) and mitral valve prolapse (MVP) has only been described in case reports. Little is known about genetic and phenotypic characteristics of these patients. Objective: To describe the prevalence, genetics, and imaging characteristics of MVP in ARVC patients. Methods: We identified 111 definite ARVC cases through medical record review, arrhythmia/cardiomyopathy targeted gene panels, and contrast cardiac magnetic resonance data. MVP was diagnosed on echocardiography as mitral leaflet displacement greater than 2 mm above the annular plane in systole, with borderline MVP defined as less than or equal to 2 mm. Results: We found MVP/borderline MVP in 14% of ARVC patients. Cardiac arrest occurred in 20% of those with MVP/borderline MVP compared to 16% without valve abnormalities. Among 69 ARVC patients with identified genetic variants, PKP2 mutations were highly prevalent (64%), particularly in those with MVP (83%). Most MVPs had posterior prolapse (73%) and trace/mild mitral regurgitation (87%). None had mitral annular disjunction. ARVCs with MVP had higher LV mass (93 vs. 75 g/m2, p = 0.02) and a higher prevalence of LV wall motion abnormalities (27% vs. 5%, p = 0.02) compared to ARVCs without valve abnormalities. Conclusions: MVP is prevalent in ARVC and characterized by PKP2 variants in most cases. Typical features of arrhythmic MVP like bileaflet involvement and annular disjunction are rare in ARVC with MVP; features of arrhythmogenic left-sided cardiomyopathy (increased LV mass index and wall motion abnormalities) are more common. Further studies are needed to understand the role of MVP in arrhythmic risk stratification of ARVC.

BACKGROUNDSotalol loading intravenously enables achieving blood levels of sotalol that are observed at maximal steady-state concentration (Cmax ss) in one-day permitting the measurement of maximum QTc effects. Rapid evaluation of the QTc effects permits determination of arrhythmic risk and thus permits discharge in 24-hours instead of the usual three-day oral load hospitalization. Given the expense of IV Sotalol an oral loading test strategy is presented that also achieves Cmax ss blood levels rapidly, permitting a one-day hospitalization for QTc evaluation. METHODPharmacokinetic parameters referred to in the literature derived from normals as well as patients was utilized for population pharmacokinetic modeling and simulation.to obtain the Cmax ss concentrations for patients with normal renal function, creatinine clearance (CrCl) > 90 ml/min), as well as for patients with a CrCl of 60-89, 30-59, and 10-29 ml/min). Using pharmacokinetic simulations, an oral loading dose, as well as a second oral dose were determined that would reach the estimated Cmax ss in each of the groups based on renal function. RESULTSFor target dosing of 120 mg oral sotalol BID in patients with a CrCl >90 ml/min an oral loading dose of 200 mg provides a peak sotalol level of 1,420 ng/ml in 3-4 hours post dosing. The Cmax ss target is 1,299 ng/ml resulting in a 9% overshoot. The Cmax ss concentration provides a means of evaluating QTc effects within 24-hours. Oral loading regimens are described for varying additional renal function levels (CrCl 60-90, 30-59 and 10-29 ml/min) along with the time to first oral dose and follow-up dosing. The initial test dose can be based on an 80 or 120 mg oral sotalol maintenance dosing strategy. CONCLUSIONSEmploying an oral loading strategy may permit QTc evaluation and one-day discharge, preserving the pharmacoeconomic advantage of a Cmax ss test strategy. Clinical PerspectiveO_ST_ABSWhat is Known?C_ST_ABSO_LIIntravenously loading of sotalol enables achieving blood levels that are observed at maximal steady-state concentration (Cmax ss) in one-day permitting the measurement of maximum QTc effects. C_LIO_LIRapid evaluation of the QTc effects permits determination of arrhythmic risk and thus permits discharge in 24-hours instead of the usual three-day oral load hospitalization C_LI What the Study AddsO_LIWith oral sotalol loading, the Cmax ss can also be achieved in one-day permitting the measurement of maximum QTc effects and discharge from the hospital in 24-hours instead of the usual three-day inpatient initiation of oral sotalol. C_LI

Catheter ablation is an established rhythm-control strategy for atrial fibrillation, but outcomes in persistent atrial fibrillation (PsAF) remain heterogeneous across evolving strategies and energy modalities. An updated synthesis is needed to define current effectiveness and adverse-event profiles in the modern ablation era. We conducted a systematic review and meta-analysis of prospective clinical trials of catheter ablation for PsAF published from 2010 through December 2025. We included randomized and nonrandomized prospective interventional studies reporting effectiveness and adverse events, and pooled outcomes using random-effects models. Prespecified subgroup analyses evaluated ablation strategy (pulmonary vein isolation [PVI] vs PVI with adjunctive lesion sets [PVI+]), ablation modality (radiofrequency [RF], cryoballoon [CRYO], and pulsed field [PF]), and endpoint definition (recurrence-only vs composite measures). Thirty-two studies (9,194 patients) met inclusion criteria; 28 (7,948 patients) contributed to effectiveness analyses. The pooled 12-month arrhythmia-free proportion was 0.65 (95% CI, 0.61-0.68), with substantial heterogeneity. Effectiveness was numerically higher with PVI+ than PVI-only (0.66 [0.60-0.72] vs 0.63 [0.59-0.67]), similar for PF (0.65 [0.57-0.72]) and RF (0.65 [0.61-0.69]), and slightly lower for CRYO (0.64 [0.54-0.74]). Recurrence-only endpoints yielded higher effectiveness than composite endpoints (0.67 [0.63-0.71] vs 0.60 [0.55-0.64]). Safety analyses included 32 studies (9,002 patients). Adverse events were low but heterogeneous (0%-14.56%); pooled vascular access and pericardial complication incidences were each 1%, while thromboembolic events, accessory organ injury, and mortality were rare (pooled 0%). PF ablation showed numerically lower overall complication incidences than RF and CRYO. In contemporary trials, catheter ablation for PsAF shows moderate effectiveness and low overall adverse-event risk. Adjunctive strategies and PF ablation are promising, but no approach is consistently superior. These findings support tailored, patient-specific ablation selection in PsAF.

BackgroundDoxorubicin (DOX) causes sex-specific cardiotoxicity. Metabolic impairment is a well-established cardiotoxic effect of DOX treatment that can contribute to other detrimental effects such as increased reactive oxygen species, reduced ATP, inflammation etc. We hypothesized that preserving cardiac metabolism by exercise can attenuate DOX cardiotoxicity. MethodsMale and female C57BL/6J mice at 15 weeks of age were randomly assigned to one of four groups, 1) Control (sedentary), 2) EX (exercised, treadmill running), 3) DOX (doxorubicin at 5 mg/kg/week for 6 weeks), and 4) EXDOX (exercise + doxorubicin). Echocardiography was performed every other week during the 6-week protocol to measure cardiac mechanical function. At the end of the protocol, optical mapping and seahorse analysis were performed to measure electrophysiology and metabolism, respectively. RNA sequencing, cytokine array assay and transmission electron microscopy were also performed to determine sex-specific mechanisms of DOX cardiotoxicity. ResultsDOX reduced stroke volume and left ventricular diameter in males only and exercise did not prevent these effects of DOX. In female mice, DOX prolonged action potential duration (APD) and slowed conduction velocity (CV), and importantly, exercise prevented DOX-induced CV slowing. Exercise-induced cardioprotection against DOX in female mice was associated with preservation of aerobic metabolism and attenuation of inflammation which modulated ion channel gene expression. Specifically, Cacna1c was increased in both DOX and EXDOX females, but not in males and correlated with APD prolongation. Interestingly, despite CV slowing, Gja1 and Scn5a were increased. However, increased Kcnj8 along with metabolic impairment could cause membrane hyperpolarization and underlie CV slowing. ConclusionsDOX cardiotoxicity is sex specific. Mechanical dysfunction is more prevalent in DOX-treated males while arrhythmogenic electrical remodeling is more prevalent in DOX-treated females. Exercise therapy during DOX did not prevent DOX induced mechanical dysfunction in male hearts but attenuated electrical remodeling in females by preserving metabolism and attenuating inflammation.

Drug-induced inhibition of the delayed rectifier potassium (IKr) current predisposes to early afterdepolarisations (EADs) and cardiac arrhythmias. Here, we sought to determine the contribution of action potential duration (APD), APD variability and spontaneous calcium release from the sarcoplasmic reticulum (SR) in the formation of EADs. In isolated sheep ventricular myocytes, EADs were induced by combined inhibition of IKr with dofetilide and {beta}-adrenergic stimulation. The onset of EADs was preceded by increased beat-to-beat variability of APD. To isolate the role of APD in EAD initiation, the sarcoplasmic reticulum (SR) was depleted of calcium with caffeine. The first beat post-caffeine was associated with prolonged APD but not an EAD. During {beta}-AR stimulation, increasing ryanodine receptor open probability had no effect on APD but increased APD variability and induced both EADs and delayed afterdepolarisations (DADs). Targeting RyR open probability with K201 reversibly abolished afterdepolarisations. APD variability was a better predictor of EADs than APD alone. During an EAD, changes in [Ca2+]i preceded those of membrane depolarisation and the changes in [Ca2+]i were in the form of calcium sparks. In silico modelling demonstrated that membrane time constant effects account for the delay between changes in [Ca2+]i and membrane potential. In summary, using a drug-induced model of action potential prolongation with {beta}-AR stimulation, EADs are preceded by increased APD variability and an increase in Ca2+ sparks. Targeting SR function abolishes EADs. These results suggest a key role for SR Ca2+ overload in the formation of EADs and indicate that EADs and DADs share common mechanisms. Key PointsO_LIDrugs that prolong the cardiac action potential and ECG QT interval are a major cause of early afterdepolarisations and dangerous ventricular arrhythmias initiated by early afterdepolarisations. C_LIO_LIProlongation of the action potential is widely assumed to be the primary driver of these events. C_LIO_LIWe show that early afterdepolarisations are instead preceded by increased beat-to-beat variability of action potential duration and that this variability has better sensitivity and specificity for early afterdepolarisations than action potential duration. C_LIO_LISmall, spontaneous calcium release events known as calcium sparks occur before membrane depolarisation driving early afterdepolarisations. C_LIO_LISuppressing calcium release from the sarcoplasmic reticulum abolishes early afterdepolarisations, identifying calcium handling instability as potentially a key mechanism of drug-induced arrhythmia. C_LI

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

Background: Andersen-Tawil syndrome type 1 (ATS1) is caused by loss-of-function mutations in KCNJ2, which encodes the inward rectifier K+ channel Kir2.1, a key determinant of IK1. Impaired Kir2.1 destabilizes membrane excitability and predisposes to ventricular arrhythmias. Most ATS1 variants disrupt channel regulation by phosphatidylinositol 4,5-bisphosphate (PIP2), but whether specific mutations confer differential arrhythmic risk remains unclear. Objective: To determine whether ATS1 variants disrupting Kir2.1-PIP2 interactions define distinct arrhythmic risk profiles and establish a mechanistically informed framework for risk stratification. Methods: We performed a pooled patient-level analysis of 225 ATS1 patients carrying KCNJ2 variants impairing Kir2.1-PIP2 interaction. Inclusion of 22 clinical and electrocardiographic variables were used to identify mutation-specific risk profiles and predictors for arrhythmia risk. The approach was validated in a multicenter cohort of 20 ATS1 patients. Functional validation was performed using patient-derived iPSC-CMs, cardiac-targeted mouse models, and structural in silico analyses. Results: ATS1 variants segregated into three discrete clusters corresponding to high-, intermediate-, and low-risk arrhythmic phenotypes, establishing a mutation-dependent hierarchy of arrhythmic risk. Regression analyses identified six variables independently associated with severe arrhythmic outcomes. Patient-derived iPSC-CM demonstrated graded impairment of electrical propagation and arrhythmia susceptibility, with a hierarchy in conduction velocity, CV:Control > R82W > R218W > G215D). Cardiac-targeted ATS1 mouse models reproduced the clinical risk stratification. Structural modeling showed that high-risk variants localize near the channel pore and disrupt Kir2.1-PIP2 interactions through mutation-specific mechanisms. Conclusions: ATS1 caused by Kir2.1-PIP2-disrupting variants is not a uniform disorder but comprises biologically distinct subgroups with predictable differences in arrhythmic severity. Integrating genetics, functional phenotyping, and structural modeling provides a mechanistically grounded framework for ATS1 risk stratification and precision therapy development.

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.

Background Heterotaxy (HTX) describes abnormal left-right arrangement of the organs, often associated with complex congenital heart disease (CHD). HTX is enriched in the respiratory condition primary ciliary dyskinesia (PCD) due to defective nodal cilia. A subset of patients presents with HTX and mild respiratory phenotypes but normal respiratory cilia function. The mechanisms underlying situs defects in these non-PCD patients remain unclear. Methods Retrospective diagnostic data were analysed from 73 HTX patients who had been referred to the Royal Brompton Hospital PCD Diagnostic Service (1997 to 2023). Data included clinical history, high-speed video microscopy, transmission electron microscopy of ciliary ultrastructure, PCD genotype and clinical imaging for cardiac and abdominal situs. Results 30 patients were diagnosed with PCD, and 43 patients did not have PCD. CHD was observed in both PCD and non-PCD groups. Atrioventricular discordance was more frequent in non-PCD HTX (20.9% vs 0%; p=0.0102). Midline Liver position was also enriched in the non-PCD HTX group compared to PCD patients with HTX (54.3% vs 25.9% p=0.0377). TEM revealed 24.4% of the non-PCD patients had extra ciliary microtubules and 24.4% demonstrated microtubular disorganization. Review of diagnostic results from 2,823 referred patients showed a higher incidence of ultrastructural ciliary anomalies, such as extra microtubules or microtubular disorganisation, in individuals with CHD who did not have PCD (p=0.04 when compared to patients without CHD, regardless of HTX). Quantitative ciliary function assessment demonstrated preserved or higher ciliary beat amplitude in non-PCD HTX compared to PCD patients. Conclusions In conclusion, HTX can be linked to respiratory ciliary dysfunction, even in patients without classical PCD. Subtle ciliary defects in non-PCD HTX patients associate with higher rates of CHD and abnormal organ situs. Genetic and phenotypic diversity in HTX highlights the need for expanded genetic testing and future multicentre studies to assess outcome.

Background Atrial fibrillation (AF) is a leading cause of stroke, cardiovascular morbidity, and mortality. Atrial myopathy, characterized by progressive metabolic, electrical, and structural changes, creates the arrhythmogenic substrate that drives AF. Defining the key drivers of atrial myopathic processes is essential for targeted therapies that can mitigate AF progression. Here we explore how reduced ERBB4 expression contributes to the development of left atrial myopathy. Methods We analyzed the Cleveland Clinic Biobank to compare left atrial ERBB4 levels in patients grouped by AF diagnosis. To investigate the impact of reduced ERBB4 levels on atrial tissue substrate, we created mouse models of cardiac-specific Erbb4 deficiency using Mlc2a (myosin light chain 2a)-Cre. Comprehensive physiological assessments were performed. Transcriptomic analyses of the left atrium were performed in an Erbb4 haploinsufficient mouse model and compared with human atrial datasets. Molecular validation of key dysregulated pathways was performed. Results We found that left atrial ERBB4 levels are reduced in patients with AF. Adult cardiomyocyte-specific Erbb4 heterozygous (Erbb4fl/+;Mlc2a-Cre) mice exhibited prolonged P-wave duration in the absence of ventricular dysfunction. Left atrial transcriptomic analysis in Erbb4 haploinsufficient mice showed upregulation of pathways related to fibrosis, apoptosis, and coagulation, and downregulation of pathways related to fatty acid metabolism and mitochondrial function, mirroring changes observed in pressure overload mouse models. A cross-species transcriptomic comparison revealed significant overlap between ERBB4-correlated gene expression and functional pathways in adult human atria and mice with Erbb4 haploinsufficiency. Validating the transcriptomic data, protein and functional assays demonstrated increased fibrosis, apoptosis, and oxidative stress in the mutant left atrial tissue. Conclusion Left atrial ERBB4 levels are reduced in AF patients. A mouse model of Erbb4 deficiency and human atrial transcriptomic analyses highlight a role for ERBB4 in supporting normal atrial metabolism while protecting against inflammation, apoptosis, and fibrosis.

Background: Higher METS-IR has been shown to be associated with a higher risk of major adverse cardiovascular events, but data are lacking regarding cardiac arrhythmias. Objectives: The aim of this study was to assess the association between METS-IR and atrial fibrillation/flutter, ventricular arrhythmia and bradyarrhythmia. Methods: Data from the Atherosclerosis Risk in Communities study spanning 1987 to 2013 was utilized for this analysis. METS-IR scores were assessed at baseline (1987-1989) and arrhythmia episodes were identified using ICD-9 codes. Multivariate-adjusted Cox proportional hazard models were constructed to evaluate the relationship between METS-IR and arrhythmia risk, with dose-response analyses conducted. In addition, we analyzed the predictive value of METS-IR for arrhythmias. Results: Over a mean follow-up of 21.9 years, 2493 cases of AF, 688 cases of bradyarrhythmia, and 1315 cases of ventricular arrhythmia were recorded. Each interquartile range increase in METS-IR was associated with a 49% higher risk of atrial fibrillation(P<0.001), 29% higher risk of bradyarrhythmia(P<0.001), and 42% higher risk of ventricular arrhythmia(P<0.001). After correction for relevant confounders, the METS-IR index was significantly and positively associated with the risk of new-onset atrial fibrillation, bradyarrhythmia, and ventricular arrhythmia (P overall<0.05, P for non-linearity>0.05). Most of the results of the subgroup analyses were not significantly different. The inclusion of METS-IR in the base model improves the predictive value of the risk of arrhythmogenesis. Conclusions: There is a significant association between METS-IR and increased risk of arrhythmias.