Background Cardiac magnetic resonance (CMR) image integration technologies offer promise to guide delineation of ventricular scar and arrhythmogenic substrate; however, there are limited co-registered histological data or comparative studies of commonly used CMR segmentation tools for ventricular tachycardia (VT) ablation. Objectives This study sought to validate 2 commonly used vendor systems (ADAS-3D and inHEART) to integrate CMR late gadolinium enhancement to electroanatomic mapping in catheter ablation of VT. Methods Five sheep underwent anteroseptal infarction with electroanatomic mapping (129 ± 12 days postinfarct). A whole heart histological model of the postinfarction scar was created. CMR was segmented by ADAS-3D and inHEART and validated with histology for 3 layers (the endocardium, intramural layer, and epicardium). A subsequent clinical validation study was performed with 5 human subjects (1 postinfarction VT, 4 nonischemic cardiomyopathy). Critical sites of VT and functional substrate (deceleration zones) were matched to ADAS-3D and inHEART scar. Results CMR-based ADAS-3D and inHEART have comparable accuracy (>75%) with moderate agreement to identify endocardial and intramural scar compared to gold standard whole-heart histology but poorer performance (modest accuracy [60%-68%] and fair agreement in the epicardial layers). Both technologies performed poorly to identify noncompact scar. Critical sites of VT colocalize reliably with ADAS-3D and inHEART scar (88% falling within 1 scar layer). More than 80% of VT critical sites demonstrated CMR late gadolinium enhancement scar in more than 1 layer. Conclusions ADAS-3D and inHEART image integration provide similar characterization of scar distribution and allowed similar display of the anatomic relation of critical re-entry circuit sites detected by mapping to scar. However, limitations exist in the performance of these technologies to identify epicardial and noncompact scar.

Introduction Atrial fibrillation (AF), a common arrhythmia, is associated with impaired quality of life and increased stroke risk and mortality. Clinical guidelines recommend leveraging digital technologies to support patient education and AF self-management. Conversational artificial intelligence (AI) technologies may support patient engagement with self-management by enabling human-like conversations. This study aims to evaluate the effectiveness of a conversational AI intervention (Conversational artificial intelligence HeAlth supporT in Atrial Fibrillation Self-Management (CHAT-AF-S)) in improving quality of life in patients with AF. Methods and analysis CHAT-AF-S is a 3-month randomised controlled trial with 1:1 allocation and embedded process evaluation. We will randomise 480 adults (aged 18 years and older) with documented AF to the CHAT-AF-S intervention or usual care. Primary outcome is the Atrial Fibrillation Effect on QualiTy-of-life overall score. We will follow the intention-to-treat principles and data analysts will be blinded. Intervention participants will be invited to complete a user experience survey and take part in an interview to explore the feasibility, acceptability, perceived use and barriers and enablers to implementing the intervention. Qualitative data will be analysed thematically. Ethics and dissemination Ethics approval was obtained from the Western Sydney Local Health District Human Ethics Research Committee (2023/ETH00765). Written and informed consent will be obtained from all study participants before commencing any study procedures. Results will be disseminated via peer-reviewed publications and presentations at international conferences. Trial registration number Australian New Zealand Clinical Trials Registry (registration number: ACTRN12623000850673).

Introductory Paragraph Multiple regulatory mechanisms govern cardiomyocyte proliferation including epigenetic modifications, metabolism and mechanical load. However, it is unclear whether such mechanisms can be pharmacologically targeted to induce cardiomyocyte proliferation without affecting other cell types. Here, we develop a dual-reporter ( TNNT2 eGFP ; PCNA mScarlet-I ) and a high-throughput image-based pipeline in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, with counter screening in non-myocytes, to identify compounds that selectively promote cardiomyocyte proliferation without affecting other cell types. We identify the PIM kinase inhibitor GDC-0339 as a cardiomyocyte-selective pro-proliferative compound. GDC-0339 induced proliferation of hiPSC-derived cardiomyocytes without activity in non-myocytes, non-cardiac fibroblasts or epithelial cells. Phosphoproteomic profiling of GDC-0339 in cardiomyocytes and non-cardiac fibroblasts revealed a cardiomyocyte-specific mechanism of action involving sarcomere disassembly via remodelling of the F-actin cytoskeleton and metabolic reprogramming to anaerobic metabolism via Pyruvate Dehydrogenase Kinases (PDKs). Thus, we uncover cardiomyocyte-specific mechanisms governing the cell cycle that are potentially druggable.

Recombinant adeno-associated virus (rAAV) vectors are widely used for in vivo gene therapy, yet their potential to integrate into the host genome raises concerns about insertional mutagenesis and oncogenic risk, particularly in the liver where vector exposure is highest. To address this, we analyzed rAAV integration patterns in primary human hepatocytes xenografted into FRG mouse livers and in hepatocytes from cynomolgus macaques following systemic rAAV administration. High-resolution integration site mapping yielded approximately 1.5 million and 1.3 million unambiguously mapped sites in human and macaque genomes, respectively. Both datasets revealed a bias toward integration within transcriptionally active genes and regions of open chromatin, consistent with previous reports, but no particular preference for genes implicated in hepatocellular carcinoma was observed. While numerous common integration sites (CISs) were identified, their distribution differed between species. Notably, a CIS was observed at the AAVS1 locus in human hepatocytes, raising the possibility of Rep-mediated integration. These findings highlight the need for continued monitoring of integration events in clinical settings. Overall, the data support a low oncogenic risk profile for the evaluated vector while reinforcing the value of direct human liver integration analyses to refine risk assessment and guide the development of safer gene therapy platforms.

BACKGROUND:Very high-power short-duration (vHPSD) radiofrequency ablation (RFA) is an alternative strategy for pulmonary vein isolation. However, rapid temperature rises may cause complications. The QDOT Micro is designed to detect temperature rises for automatic power and irrigation flow adjustments. We compared how differences in ablation electrode design between three RFA catheters impact vHPSD lesions. METHODS:vHPSD RFA was performed within a validated gel tank model. Four-second ablations were delivered with stable contact force using the QDOT, SmartTouch, and TactiFlex SE at 60, 70, 80, and 90 watts, positioned perpendicular (90°), oblique (45°), and parallel (0°) to the ablation target, utilizing 0.9% and 0.45% "half-normal" saline (HNS) irrigation. The SmartTouch and TactiFlex were operated in power-controlled mode, and each configuration was repeated three times, with images captured every second to characterize lesions. RESULTS:In total, 216 vHPSD lesions were delivered. At 90 W, 90°, and 0.9% saline, the QDOT produced lesions with a mean depth of 1.93 mm. The TactiFlex produced shallower lesions, with a mean depth of 1.88 mm (p = 0.02), and the SmartTouch produced the deepest, with a mean depth of 2.37 mm (p < 0.001). The mean diameter of QDOT lesions, at 4.63 mm, was comparable to TactiFlex lesions (4.58 mm, p = 0.8), whilst the SmartTouch lesions were significantly wider than both the QDOT and TactiFlex (6.04 mm, p < 0.001). Steam-pop risk, based on lesion temperature, was lowest for the TactiFlex. CONCLUSION:vHPSD lesions produced with the QDOT achieved greater dimensions and temperatures than those with the TactiFlex under controlled conditions, suggesting a difference in the cooling profile of the ablation electrodes. vHPSD with the SmartTouch or 0.45% HNS are likely to increase the risk of steam pops.

Myocardial infarction (MI) contributes to significant morbidity and mortality globally. Platelet derived growth factor-AB (PDGF-AB) is potentially a novel translational therapeutic for improving cardiac function post-MI, which we assess here using a 60 day porcine left anterior descending artery occlusion ischemia-reperfusion model. MI was induced in 10 female Landrace swine, with 5 controls, 5 receiving PDGF-AB treatment and 2 additional shams. PDGF-AB improved left ventricular ejection fraction 58 days after MI, without affecting overall infarct scar size, as shown using serial cardiac magnetic resonance imaging. Preserved infarct zone microvascular function and increased vessel maturity was also observed. Multi-omic analyses showed that PDGF-AB treatment altered the expression of proteins, metabolites, and lipids that are known to be involved in myocardial energetics and redox balance. Novel therapeutics such as PDGF-AB may lead to more sustained salvage of cardiac function by modulating the post-MI microvasculature, myocardium and extracellular matrix.

Background Accurate electroanatomic mapping is critical for identifying scar and the long-term success of ventricular tachycardia ablation. Objectives This study sought to determine the accuracy of multielectrode mapping (MEM) catheters to identify scar on cardiac magnetic resonance (CMR) and histopathology. Methods In an ovine model of myocardial infarction, we examined the effect of electrode size, spacing, and mapping rhythm on scar identification compared to CMR and histopathology using 5 multielectrode mapping catheters. We co-registered electroanatomic mapping, CMR, and histopathology for comparison. Catheter-specific voltage thresholds were identified based on underlying amounts of normal myocardium on transmural histology biopsies. Results Ten animals were included: 6 with anteroseptal myocardial infarction and 4 control animals. A total of 419,597 points were manually reviewed across the catheters, with 315,487 points used in the analysis. There were minimal differences in bipolar and unipolar voltages, scar areas, and abnormal electrograms between catheters and between rhythms. Catheter-specific bipolar and unipolar voltage thresholds for normal myocardium were High-Density Grid >2.78 mV and >6.19 mV, DuoDecapolar >2.22 mV and >6.05 mV, PentaRay >1.66 mV and >5.35 mV, Decanav >1.36 mV and >4.75 mV, Orion >1.21 mV and >6.05 mV, respectively. Catheter-specific bipolar thresholds improved the accuracy for detecting endo-mid myocardial scar on CMR by 1.8%-15.6% and catheter-specific unipolar thresholds improved the accuracy in the mid-epicardial layers by 25.3%-81.1%. Conclusions Minimal differences were observed in scar detection and electrogram markers between commercially available multielectrode mapping catheters and differing wave fronts. Compared to traditional voltage criteria for bipolar and unipolar scar, catheter-specific thresholds markedly improved accuracy for delineating scar on CMR.

The selection of an appropriate promoter is important to the design and optimisation of adeno-associated viral (AAV) vector-based cardiac gene therapies. The expression cassette design can impact efficacy and safety of the vector. This study is the first to use a novel AAV barcode-seq method for the simultaneous evaluation of a panel of cardiac-specific promoters in a high-throughput manner. Functional analyses of our cardiac promoter kit packaged in three different capsids were performed using neonatal rat ventricular myocytes (NRVM), human iPSC-derived cardiomyocytes (hiPSC-CMs), HuH7 hepatocellular carcinoma cells, as well as mouse, rat, sheep and pig models. The cardiac troponin T (cTnT) promoter showed the most promise overall as a cardiac-specific promoter across all cardiac models tested. The results validate the barcode-seq technique as a powerful and versatile approach that enables high-throughput, quantitative analysis of various expression cassettes in commonly used models of cardiac gene therapy.

BACKGROUND:Multiple extrastimulus (ES) pacing protocols exist for ventricular substrate mapping. Despite being increasingly adopted in clinical practice, direct protocol comparisons have been limited. This study aims to compare the substrate delineation and mapping efficiency of right ventricular pacing+ES (RVp+ES) and sensed ES pacing strategies in a large animal ischemia-reperfusion injury model. METHODS:Four swine underwent 90-minute balloon occlusion of the mid-left anterior descending artery, followed by late gadolinium-enhanced cardiac magnetic resonance between days 30 and 58 and invasive electroanatomic mapping. Late gadolinium-enhanced cardiac magnetic resonances were segmented for scar topography and border zone channel geometry. RESULTS:Sensed ES substrate maps had greater point density (12.90±4.20 pts/cm2 versus 5.75±0.52 pts/cm2; P=0.032) and faster acquisition (113.71±22.38 s/pt per cm2 versus 228.57±77.30 s/pt per cm2; P=0.027) than RVp+ES. Despite this, RVp+ES substrate maps had greater uncovering of split potentials within border zone channels (76.5% [15.4%-95.5%] versus 16.7% [0%-52.9%]; P=0.028), higher sensitivity (53% versus 30%), and similarly high specificity (91% versus 93%) than sensed ES, as well as better visual correlation on decrement-evoked potential maps. Bipolar voltage in sinus rhythm and RVp did not reliably predict tissue response to ES, with 46% to 57% of split potentials within border zone channels arising from seemingly normal voltage (≥1.5 mV). CONCLUSIONS:RVp+ES is more sensitive than sensed ES and highly specific for the detection of late gadolinium-enhanced cardiac magnetic resonance border zone channels postmyocardial infarct.

Accurate delineation of scar patterns is valuable for guiding catheter ablation of ventricular tachycardia. We hypothesized that scar and its pattern of distribution can be determined from intracardiac electrograms using computational signal processing and that further improvements in classification can be achieved with a convolutional neural network. A total of 5 sheep underwent anteroseptal infarction (plus 1 healthy control) with electroanatomic mapping (129±12 days post-infarct). A whole-heart histological model of the postinfarction scar was created and coregistered to ventricular electrograms. Electrograms were matched to scar pattern categories; no scar, at least endocardial scar: at least intramural scar (intramural scar sparing the endocardium), or epicardial-only scar (epicardial scar sparing the endocardium/intramural space). A suite of signal-processing features was extracted from bipolar electrograms. Furthermore, bipolar and unipolar electrograms were used to train a time series convolutional neural network (InceptionTime). A total of 11 551 electrograms were matched to 451 biopsies. Bipolar and unipolar voltage alone were poor classifiers of scar patterns. For each of the scar labels, 20 bipolar electrogram features (predominantly within the frequency domain) yielded an area under the curve of 0.815, 0.810, 0.704, and 0.681 to predict no scar, at least endocardial scar, at least intramural scar, and epicardial-only scar, respectively. Substantial improvement was achieved with a convolutional neural network trained on unipolar electrograms: areas under the curve and accuracy (averaged across wavefronts) were 0.977 and 0.929 for no scar, 0.970 and 0.919 for at least endocardial scar, 0.909 and 0.959 for at least intramural scar and 0.926 and 0.958 for epicardial-only scar. Convolutional neural network-derived analysis of unipolar electrogram data has excellent predictive value for determination of scar patterns. Computational analyses of electrogram data beyond voltage and other time-domain features are necessary to improve the identification of arrhythmogenic sites in the ventricle.

INTRODUCTION:Atrial cardiomyopathy (ACM) is characterized by complex interactions involving molecular, electrical, and structural abnormalities that predispose individuals to cardiac dysfunction and stroke. Current treatments are effective at managing the complications of ACM, but lack the ability to correct the underlying atrial substrate driving the disease state. Alternative treatment modalities are required to address this shortfall with viral-based delivery methods, particularly recombinant adeno-associated viral vectors (rAAVs), being at the forefront of filling this unmet need. Research in the design of rAAVs targeting the atrial myocardium has demonstrated robust atrial transduction with minimal toxicity. Despite the technology's promise, various biological, immunological, and economic obstacles continue to challenge the clinical translation of rAAVs targeting ACM. AREAS COVERED:In this review, the concept of ACM is summarized along with its common sequelae and current management. Following this, a basic overview of rAAV biology is provided alongside a narrative review of research investigating rAAV-based gene therapy targeting atrial myocardium in preclinical models. EXPERT OPINION:Gene therapies provide an opportunity to treat ACM at the root cause beyond the management of its sequelae. However, solutions aiming to improve vector design, manufacturability and suitability for ACM should be adopted to improve therapeutic efficacy and broaden patient accessibility.

Ghrelin is commonly known as the ‘hunger hormone’ due to its role in stimulating food intake in humans. However, the roles of ghrelin extend beyond regulating hunger. Our aim was to investigate the ability of ghrelin to protect against hydrogen peroxide (H2O2), a reactive oxygen species commonly associated with cardiac injury. An in vitro model of oxidative stress was developed using H2O2 injured H9c2 cells. Despite lentiviral ghrelin overexpression, H9c2 cell viability and mitochondrial function were not protected following H2O2 injury. We found that H9c2 cells lack expression of the preproghrelin cleavage enzyme prohormone convertase 1 (encoded by PCSK1), required to convert ghrelin to its active form. In contrast, we found that primary rat cardiomyocytes do express PCSK1 and were protected from H2O2 injury by lentiviral ghrelin overexpression. In conclusion, we have shown that ghrelin expression can protect primary rat cardiomyocytes against H2O2, though this effect was not observed in other cell types tested.

Aims Embolic stroke of undetermined source (ESUS) results in significant morbidity. A left atrial (LA) myopathy is implicated in a proportion of these patients. We hypothesized that LA shape varies by cause of stroke [CE (cardioembolic) vs. ESUS]. Methods and results A total of 236 ischaemic stroke and atrial fibrillation (AF) patients and controls were recruited prospectively. AF was classified as paroxysmal AF (PAF) or persistent AF (PersAF). Stroke patients comprised CE stroke secondary to AF and ESUS. There were 81 AF (47 PAF, 34 PersAF), 50 ESUS, 57 CE patients [subdivided into CE with PAF (CEpaf) and CE with PersAF (CEpers)], and 48 controls. Echocardiographic parameters including LA volume, function, and shape/sphericity (3D LA sphericity and 2D-derived LA circularity, ellipticity, sphericity, and eccentricity indices) were evaluated. Increased LA volume and sphericity with LA dysfunction were present in CE, AF, and ESUS groups compared with controls. K-means cluster analysis demonstrated a spectrum of LA myopathy with controls at the lowest and CEpers and PersAF at the upper extremes, with ESUS, PAF, and CEpaf being similar and falling between these extremes. After adjusting for age, sex, and left ventricular (LV) and LA parameters, LA sphericity markers differentiated ESUS from controls (P < 0.01). Conclusion Alterations in LA shape are present in ESUS, AF, and CE patients, particularly increased spherical remodelling. The novel markers of LA sphericity proposed may identify LA myopathy in ESUS patients and potentially guide management for secondary prevention.

BACKGROUND:Ischaemic stroke remains one of the leading causes of death and disability worldwide. The population of Western Sydney has a unique demographic with lower socioeconomic status and a culturally and linguistically diverse population. This study aims to investigate the demographics and cardiovascular risk factors of patients in Western Sydney, focusing on the prevalence and profile of cardioembolic (CE) strokes and embolic strokes of undetermined source (ESUS). METHOD:Prospective data were collected in 463 patients with ischaemic stroke presenting to a tertiary centre in Western Sydney, who underwent predischarge transthoracic echocardiography. Patients with haemorrhagic strokes or unclear stroke diagnosis were excluded. Analysis of stroke subtype (CE, ESUS, or non-embolic) and clinical characteristics was performed based on age, gender, and prior atrial fibrillation (AF) prevalence. RESULTS:Of the 463 patients, 147 (32%) had CE strokes, and 147 (32%) had ESUS. Cardioembolic (CE) strokes were associated with older age (≥65 years) and a history of congestive cardiac failure. Older patients had higher rates of hypertension, ischaemic heart disease, AF, and congestive heart failure. History of AF was present in 67 patients (14.5%); however, only 51% received anticoagulation before admission despite a low bleeding risk. The transthoracic echocardiography characteristics of ESUS/non-embolic strokes differed from those of CE strokes; 20% of patients with ESUS had an enlarged left atrium, suggesting a subset of patients with ESUS with a left atrial myopathy. CONCLUSIONS:Patients with ischaemic stroke in Western Sydney have a high prevalence of cardiovascular risk factors which were often undertreated. Half of the patients with prior AF did not receive anticoagulation despite low bleeding risk, indicating a gap in optimal stroke prevention. There were distinct echocardiographic characteristics among stroke subtypes. Further analysis of left atrium parameters may provide greater insights into the pathogenesis and prevention of embolic strokes.

AbstractBackgroundCardiac amyloidosis (CA) is an under‐recognized cause of heart failure. Left atrial (LA) myopathy contributes to a worse prognosis in heart failure and is a feature of transthyretin (ATTR) and light‐chain (AL) CA. LA mechanical dispersion (LA‐MD) is a novel marker of intra‐atrial dyssynchrony implicated in LA myopathy and the future development of atrial fibrillation (AF).AimsThis study aimed to determine the characteristics and prognostic value of LA myopathy in ATTR and AL cardiomyopathy through a comprehensive LA echocardiographic evaluation.MethodsATTR (n = 86) and AL (n = 86) CA patients were compared with hypertensive heart disease (HHT) patients (n = 58). Transthoracic echocardiographic measurements including LA strain and LA‐MD were obtained with patient follow‐up for mortality.ResultsATTR and AL patients had a median follow‐up of 66 months, with 26 mortality events. Left ventricular (LV) mass, diastolic function (average‐e′ and E/e′), LV global longitudinal strain, and LA volume and function (LA function index and strain) were more impaired in ATTR versus AL; these echocardiographic parameters were more impaired in both amyloid groups compared to HHT patients (P < 0.05). LA‐MD was increased in ATTR versus AL [median 72.2 (inter‐quartile range 55–88.9) vs. 54 (43.5–64.2), respectively, P < 0.001]. Multivariable logistic regression adjusted for age, presence of AF, LV mass, global and basal strain, and E/e′ demonstrated that LA‐MD was an independent determinant of ATTR CA (P = 0.014). On multivariable analysis, LA reservoir strain was independently associated with the presence of heart failure in the CA group (P < 0.001). LA minimum volume (cut‐off ≥18 mL/m2) was a determinant of mortality in AL CA [Cox proportional hazard ratio (HR) 1.042 (1.003–1.082), P = 0.034 and Kaplan–Meier analysis, P = 0.016].ConclusionCharacterizing LA myopathy has significant diagnostic and prognostic utility in CA. ATTR patients have increased atrial dyssynchrony, which may have implications for AF development. LA reservoir strain was associated with heart failure in CA, whilst LA minimum volume was a predictor of mortality in AL CA.