Short-term wind speed forecasting based on a hybrid model of ICEEMDAN, MFE, LSTM and informer

Wind energy, as a kind of environmentally friendly renewable energy, has attracted a lot of attention in recent decades. However, the security and stability of the power system is potentially affected by large-scale wind power grid due to the randomness and intermittence of wind speed. Therefore, accurate wind speed prediction is conductive to power system operation. A hybrid wind speed prediction model based on Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN), Multiscale Fuzzy Entropy (MFE), Long short-term memory (LSTM) and INFORMER is proposed in this paper. Firstly, the wind speed data are decomposed into multiple intrinsic mode functions (IMFs) by ICEEMDAN. Then, the MFE values of each mode are calculated, and the modes with similar MFE values are aggregated to obtain new subsequences. Finally, each subsequence is predicted by informer and LSTM, each sequence selects the one with better performance than the two predictors, and the prediction results of each subsequence are superimposed to obtain the final prediction results. The proposed hybrid model is also compared with other seven related models based on four evaluation metrics under different prediction periods to verify its validity and applicability. The experimental results indicate that the proposed hybrid model based on ICEEMDAN, MFE, LSTM and INFORMER exhibits higher accuracy and greater applicability.

Identification of non-ischaemic fibrosis in male veteran endurance athletes, mechanisms and association with premature ventricular beats

Left ventricular fibrosis can be identified by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in some veteran athletes. We aimed to investigate prevalence of ventricular fibrosis in veteran athletes and associations with cardiac arrhythmia. 50 asymptomatic male endurance athletes were recruited. They underwent CMR imaging including volumetric analysis, bright blood (BB) and dark blood (DB) LGE, motion corrected (MOCO) quantitative stress and rest perfusion and T1/T2/extracellular volume mapping. Athletes underwent 12-lead electrocardiogram (ECG) and 24-h ECG. Myocardial fibrosis was identified in 24/50 (48%) athletes. All fibrosis was mid-myocardial in the basal-lateral left ventricular wall. Blood pressure was reduced in athletes without fibrosis compared to controls, but not athletes with fibrosis. Fibrotic areas had longer T2 time (44 ± 4 vs. 40 ± 2 ms, p < 0.0001) and lower rest myocardial blood flow (MBF, 0.5 ± 0.1 vs. 0.6 ± 0.1 ml/g/min, p < 0.0001). On 24-h ECG, athletes with fibrosis had greater burden of premature ventricular beats (0.3 ± 0.6 vs. 0.05 ± 0.2%, p = 0.03), with higher prevalence of ventricular couplets and triplets (33 vs. 8%, p = 0.02). In veteran endurance athletes, myocardial fibrosis is common and associated with an increased burden of ventricular ectopy. Possible mechanisms include inflammation and blood pressure. Further studies are needed to establish whether fibrosis increases risk of malignant arrhythmic events.

Generation of an induced pluripotent stem cell line from a patient with conduction disease and recurrent ventricular fibrillation with a sodium voltage-gated channel alpha subunit 5 (SCN5A) gene c.392 + 3A > G splice-site variant

Variants in the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) produce variable cardiac phenotypes including Brugada syndrome, conduction disease and cardiomyopathy. These phenotypes can lead to life-threatening arrhythmias, heart failure, and sudden cardiac death. Novel variants in splice-site regions of SCN5A require functional studies to characterise their pathogenicity as they are poorly understood. The generation of an induced pluripotent stem cell line provides a valuable resource to investigate the functional effects of potential splice-disrupting variants in SCN5A.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Long-Term Outcomes of Permanent Pacemaker Implantation in Bicaval Heart Transplant Recipients

BACKGROUND

Permanent pacemakers (PPMs) may be necessary in up to 10% of patients after heart transplantation (HT).

OBJECTIVES

The purpose of this study was to evaluate long-term outcomes and clinical courses of heart transplant recipients who received PPM.

METHODS

All patients who required PPM after bicaval HT at Columbia University between January 2005 and December 2021 were included. Cases were compared to matched heart transplant recipients by age, sex, and year of transplantation. Patient and device characteristics including complications and device interrogations were reviewed. Outcomes of re-transplantation or graft failure/death were compared between groups.

RESULTS

Of 1,082 heart transplant recipients, 41 (3.8%) received PPMs. The median time from transplantation to PPM was 118 days (IQR: 18-920 days). The most common indications were sinus node dysfunction (60%, n = 25) and atrioventricular (AV) nodal disease (41.5%, n = 17). Post-implantation complications included pocket hematoma (n = 3), lead under-sensing (n = 2), and pocket infection requiring explant (n = 1). Rates of death and re-transplantation at 10 years post-HT were similar between groups. In multivariable analysis, after adjustment for mechanical circulatory support, pretransplantation amiodarone use, donor ischemic time and age, only older donor age was associated with increased risk of PPM implantation (P = 0.03). There was a significant decrease in PPM placement after 2018 (1.2% vs 4.4%, P = 0.02), largely driven by a decline in early PPM placement. There were no differences in mortality or need for re-transplantation between groups.

CONCLUSIONS

PPMs are implanted after HT for sinus and atrioventricular node dysfunctions with low incidence of device-related complications. Our study shows a decrease in PPM implantation after 2018, likely attributable to expectant management in the early postoperative period.

Septal Substrate Ablation Guided by Delayed Transmural Conduction Times: A Novel Ablation Approach to Target Intramural Substrates

BACKGROUND

Intraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT.

OBJECTIVES

This study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes.

METHODS

We included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2).

RESULTS

There were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1.

CONCLUSIONS

In patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT.

Left bundle branch area pacing (LBBAP) Auto Threshold algorithms Evaluation for Conduction System Pacing: The LATECS pilot Trial

BACKGROUND

Automated threshold measurements (ATM) and output adaptation improved safety and follow-up of cardiac implantable devices (CIED) in the last years. These algorithms were validated for conventional cardiac pacing; however, they were not suitable for permanent His Pacing. Left bundle branch area pacing (LBBAP) is an emerging technique to obtain physiologic cardiac stimulation; we tried to assess if ATM could be applied to this setting.

METHODS

Consecutive patients receiving ATM-capable CIED and LBBAP in our hospital were enrolled in this prospective, observational trial; they were evaluated 3 months after implant, comparing pacing thresholds manually assessed and obtained via ATM. Subsequent remote follow-up was carried on when available.

RESULTS

Forty-five patients were enrolled. ATM for LBBAP lead provided consistent results in all the patients and was therefore activated; mean value of manually obtained LBBAP capture threshold was 0.66 ± 0.19 V versus ATM of 0.64 ± 0.19 V. TOST analysis showed equivalence of the two measures (p = .66). At subsequent follow-up (mean follow up 7.7 ± 3.2 months), ATM was effective in assessing pacing thresholds and no clinical adverse event was observed.

CONCLUSIONS

ATM algorithms proved equivalent to manual testing in determining capture threshold and were reliably employed in patients receiving LBBAP CIED.

Non-Coding RNAs and Gut Microbiota in the Pathogenesis of Cardiac Arrhythmias: The Latest Update

Non-coding RNAs (ncRNAs) are indispensable for adjusting gene expression and genetic programming throughout development and for health as well as cardiovascular diseases. Cardiac arrhythmia is a frequent cardiovascular disease that has a complex pathology. Recent studies have shown that ncRNAs are also associated with cardiac arrhythmias. Many non-coding RNAs and/or genomes have been reported as genetic background for cardiac arrhythmias. In general, arrhythmias may be affected by several functional and structural changes in the myocardium of the heart. Therefore, ncRNAs might be indispensable regulators of gene expression in cardiomyocytes, which could play a dynamic role in regulating the stability of cardiac conduction and/or in the remodeling process. Although it remains almost unclear how ncRNAs regulate the expression of molecules for controlling cardiac conduction and/or the remodeling process, the gut microbiota and immune system within the intricate networks might be involved in the regulatory mechanisms. This study would discuss them and provide a research basis for ncRNA modulation, which might support the development of emerging innovative therapies against cardiac arrhythmias.

Knockout of the Cardiac Transcription Factor NKX2-5 Results in Stem Cell-Derived Cardiac Cells with Typical Purkinje Cell-like Signal Transduction and Extracellular Matrix Formation

The human heart controls blood flow, and therewith enables the adequate supply of oxygen and nutrients to the body. The correct function of the heart is coordinated by the interplay of different cardiac cell types. Thereby, one can distinguish between cells of the working myocardium, the pace-making cells in the sinoatrial node (SAN) and the conduction system cells in the AV-node, the His-bundle or the Purkinje fibres. Tissue-engineering approaches aim to generate hiPSC-derived cardiac tissues for disease modelling and therapeutic usage with a significant improvement in the differentiation quality of myocardium and pace-making cells. The differentiation of cells with cardiac conduction system properties is still challenging, and the produced cell mass and quality is poor. Here, we describe the generation of cardiac cells with properties of the cardiac conduction system, called conduction system-like cells (CSLC). As a primary approach, we introduced a CrispR-Cas9-directed knockout of the NKX2-5 gene in hiPSC. NKX2-5-deficient hiPSC showed altered connexin expression patterns characteristic for the cardiac conduction system with strong connexin 40 and connexin 43 expression and suppressed connexin 45 expression. Application of differentiation protocols for ventricular- or SAN-like cells could not reverse this connexin expression pattern, indicating a stable regulation by NKX2-5 on connexin expression. The contraction behaviour of the hiPSC-derived CSLCs was compared to hiPSC-derived ventricular- and SAN-like cells. We found that the contraction speed of CSLCs resembled the expected contraction rate of human conduction system cells. Overall contraction was reduced in differentiated cells derived from NKX2-5 knockout hiPSC. Comparative transcriptomic data suggest a specification of the cardiac subtype of CSLC that is distinctly different from ventricular or pacemaker-like cells with reduced myocardial gene expression and enhanced extracellular matrix formation for improved electrical insulation. In summary, knockout of NKX2-5 in hiPSC leads to enhanced differentiation of cells with cardiac conduction system features, including connexin expression and contraction behaviour.

The evolving state of cardiac resynchronization therapy and conduction system pacing: 25 years of research at EP Europace journal

Cardiac resynchronization therapy (CRT) was proposed in the 1990s as a new therapy for patients with heart failure and wide QRS with depressed left ventricular ejection fraction despite optimal medical treatment. This review is aimed first to describe the rationale and the physiologic effects of CRT. The journey of the landmark randomized trials leading to the adoption of CRT in the guidelines since 2005 is also reported showing the high level of evidence for CRT. Different alternative pacing modalities of CRT to conventional left ventricular pacing through the coronary sinus have been proposed to increase the response rate to CRT such as multisite pacing and endocardial pacing. A new emerging alternative technique to conventional biventricular pacing, conduction system pacing (CSP), is a promising therapy. The different modalities of CSP are described (Hirs pacing and left bundle branch area pacing). This new technique has to be evaluated in clinical randomized trials before implementation in the guidelines with a high level of evidence.

Association between the accumulation of elevated serum γ-glutamyltransferase level and risk of atrial fibrillation: a nationwide cohort study

Atrial fibrillation (AF) is the most common cardiac arrhythmia. The association between AF and γ-Glutamyltransferase (GGT) was not fully established. This study demonstrated the independent association of cumulative GGT score and AF incidence with the dose-response relationship. Using the Korean National Health Insurance Corporation database, adult subjects who had 4 consecutive annual health examinations from 2009 to 2012 were enrolled. A cumulative GGT score was calculated as the cumulative number of the highest GGT quartile amongst four examinations (0-4 times). A multivariable Cox proportional hazards regression analysis was performed. Among a total of 3,500,847 people included, AF was developed in 27,752 people (0.793%) during a median of 8.0 years of follow up. The incidence rate of AF and adjusted hazard ratio were increased by a stepwise manner in the higher quartile group and cumulative GGT score group. In subgroup analysis, this trend was more prominent in the elderly, people without hypertension, non-obese people, and people without any four comorbidities (diabetes mellitus, hypertension, dyslipidemia, and obesity). Our results suggest multiple accumulation of elevated GGT levels in health examination might be a useful marker for risk stratification of AF development, especially in the elderly and healthy population.

Electrophysiology fellowship experience and requirements: an EHRA survey

AIMS

This study aims to survey current educational experience and the individual requirements for electrophysiologists in training.

METHODS AND RESULTS

The European Heart Rhythm Association (EHRA) e-Communication Committee and the Scientific Initiatives Committee prepared a questionnaire and distributed it via newsletters, Twitter, LinkedIn, and Facebook. The survey consisted of 22 questions collected on an individual basis anonymously. Two hundred and forty-three responders from 35 countries (32% female, age 38 ± 6 years old) completed the survey. This EHRA electrophysiology (EP) fellowship survey showed that (i) hands-on participation and observation of EP procedures are very important; (ii) the main motivations to choose the EP fellowship institution are centre reputation and volume as well as the availability of a structured EP fellowship programme; (iii) 59% passed the EHRA exam and 46% took a national certification exam; (iv) respondents are overall satisfied with their own fellowships, but there are areas of less confidence such as conduction system pacing implantation and cardiac resynchronization therapy implantation; (v) 78% of respondents performed research during their fellowship, (vi) the optimal duration of an EP fellowship should be at least 2 years; and (viii) doing fellowships abroad is beneficial, but significant obstacles exist.

CONCLUSION

The results of this EHRA survey may help to refine current EP fellowship programmes to improve the quality of EP training and early career building of young electrophysiologists.

Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing

AIMS

Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

METHODS AND RESULTS

Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

CONCLUSION

Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Comparison of Pacing Performance and Clinical Outcomes Between Left Bundle Branch and His Bundle Pacing

BACKGROUND

Left bundle branch (LBBP) and His-bundle pacing (HBP) provide physiological ventricular activation.

OBJECTIVES

This study investigated differences in feasibility, device performance, and clinical outcomes between LBBP and HBP.

METHODS

Consecutive patients with LBBP and HBP from 2018 to 2021 in 2 centers were prospectively studied. The primary endpoint was optimal device performance during follow-up, defined as the presence of pacing thresholds <2.5 V, R-wave amplitude ≥5 V, and absence of conduction system pacing (CSP)-related complications. The secondary endpoint was the composite of heart failure hospitalizations or all-cause mortality.

RESULTS

Among 338 patients, 282 underwent successful CSP (119 HBP, 163 LBBP). Success rates, CSP-related complications, and need for reoperations did not differ between LBBP and HBP (P > 0.05). Pacing thresholds were lower, whereas R-wave amplitudes and lead impedance were higher in LBBP (P < 0.05). The primary endpoint was more frequent in LBBP than HBP (79% vs 34%; P < 0.001), with LBBP independently associated with 9-fold increased odds of optimal device performance (adjusted OR: 9.31; 95% CI: 5.14-16.86). LBBP was less likely to have increased pacing thresholds by >1 V (1% vs 19% HBP, P < 0.001). The secondary outcome was less frequent in LBBP than HBP (9% vs 24%, P = 0.001), with LBBP trending towards higher event-free survival (HR: 0.62; 95% CI: 0.31-1.23). The secondary outcome was independent of pacing burden or pacing indication.

CONCLUSIONS

Despite similar feasibility and safety profiles, LBBP confers additional benefits in pacing performance and reliability, shows trends towards improved survival compared to HBP, and should be the preferred first-line CSP modality of choice.

Functional Epicardial Conduction Disturbances Due to a SCN5A Variant Associated With Brugada Syndrome

BACKGROUND

Brugada syndrome is a significant cause of sudden cardiac death (SCD), but the underlying mechanisms remain hypothetical.

OBJECTIVES

This study aimed to elucidate this knowledge gap through detailed ex vivo human heart studies.

METHODS

A heart was obtained from a 15-year-old adolescent boy with normal electrocardiogram who experienced SCD. Postmortem genotyping was performed, and clinical examinations were done on first-degree relatives. The right ventricle was optically mapped, followed by high-field magnetic resonance imaging and histology. Connexin-43 and NaV1.5 were localized by immunofluorescence, and RNA and protein expression levels were studied. HEK-293 cell surface biotinylation assays were performed to examine NaV1.5 trafficking.

RESULTS

A Brugada-related SCD diagnosis was established for the donor because of a SCN5A Brugada-related variant (p.D356N) inherited from his mother, together with a concomitant NKX2.5 variant of unknown significance. Optical mapping demonstrated a localized epicardial region of impaired conduction near the outflow tract, in the absence of repolarization alterations and microstructural defects, leading to conduction blocks and figure-of-8 patterns. NaV1.5 and connexin-43 localizations were normal in this region, consistent with the finding that the p.D356N variant does not affect the trafficking, nor the expression of NaV1.5. Trends of decreased NaV1.5, connexin-43, and desmoglein-2 protein levels were noted; however, the RT-qPCR results suggested that the NKX2-5 variant was unlikely to be involved.

CONCLUSIONS

This study demonstrates for the first time that SCD associated with a Brugada-SCN5A variant can be caused by localized functionally, not structurally, impaired conduction.

AFE-GAN: Synthesizing Electrocardiograms with Atrial Fibrillation Characteristics Using Generative Adversarial Networks. Annu Int Conf IEEE Eng Med Biol Soc 2023;2023:1-5. [PMID: 38083445 DOI: 10.1109/embc40787.2023.10340565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Labeled ECG data in diseased state are, however, relatively scarce due to various concerns including patient privacy and low prevalence. We propose the first study in its kind that synthesizes atrial fibrillation (AF)-like ECG signals from normal ECG signals using the AFE-GAN, a generative adversarial network. Our AFE-GAN adjusts both beat morphology and rhythm variability when generating the atrial fibrillation-like ECG signals. Two publicly available arrhythmia detectors classified 72.4% and 77.2% of our generated signals as AF in a four-class (normal, AF, other abnormal, noisy) classification. This work shows the feasibility to synthesize abnormal ECG signals from normal ECG signals.Clinical significance - The AF ECG signal generated with our AFE-GAN has the potential to be used as training materials for health practitioners or be used as class-balance supplements for training automatic AF detectors.

Evaluation of Tp-E interval and Tp-E/Qtc ratios in patients with overt hypothyroidism and subclinical hypothyroidism

OBJECTIVE

Tp-e interval and Tp-e/QTc are among the new-generation indicators used for predicting cardiac arrhythmia and ventricular repolarization. In this study, we aimed to evaluate Tp-e and Tp-e/QTc ratios in patients with overt hypothyroidism and subclinical hypothyroid patients.

PATIENTS AND METHODS

In this study, a total of 105 patients were included with 35 overt hypothyroidism, 35 subclinical hypothyroidism, and 35 healthy euthyroid patients. The anthropometric measurements, laboratory results, and electrocardiographic data of the patients were measured. The groups were compared in terms of Tp-e interval, Tp-e/QT and Tp-e QT/c ratios.

RESULTS

When the Tp-e interval and Tp-e/QTc values of the patients were compared, a significant difference was found (p<0.001). A positive correlation was found between thyroid stimulating hormone (TSH) with Tp-e interval and Tp-e/QT ratio.

CONCLUSIONS

Tp-e interval and Tp-e/QTc duration increased in overt hypothyroidism and subclinical hypothyroidism patients compared to euthyroid patients. We believe that regular use of levothyroxine therapy in overt hypothyroidism patients will decrease cardiac mortality. Cardiac risk factors should be considered to decide on levothyroxine therapy for subclinical hypothyroidism patients.

Optimization of Arrhythmia-based ECG-lead Selection for Computer-interpreted Heart Rhythm Classification

The 12-lead ECG only has 8 independent ECG leads, which leads to diagnostic redundancy when using all 12 leads for heart arrhythmias classification. We have previously developed a deep learning (DL)-based computer-interpreted ECG (CIE) approach to identify an optimal 4-lead ECG subset for classifying heart arrhythmias. However, the clinical diagnostic criteria of cardiac arrhythmia types are often lead-specific, so this study is going to explore the selection of arrhythmia-based ECG-lead subsets rather than one general optimal ECG-lead subset, which could improve the classification performance for the CIE. The DL-based CIE model previously developed was used to learn 4 common types of heart arrhythmias (LBBB, RBBB, AF, and I-AVB) for identifying corresponding optimal ECG-lead subsets. A public dataset that splits into training (approx. 70%), validation (approx. 15%), and test (approx. 15%) sets from the PhysioNet Cardiology Challenge 2020 was used to explore the study. The results demonstrated that the DL-based CIE model identified an optimal ECG-lead subset for each arrhythmia: I, II, aVR, aVL, V1, V3, and V5 for I-AVB; I, II, aVR, and V3 for AF; I, II, aVR, aVF, V1, V3, and V4 for LBBB; and I, II, III, aVR, V1, V4, and V6 for RBBB. For each arrhythmia classification, the DL-based CIE model using the optimal ECG-lead subset significantly outperformed the model using the full 12-lead ECG set on the validation set and on the external test dataset.The results support the hypothesis that using an optimal ECG-lead subset instead of the full 12-lead ECG set can improve the classification performance of a specific arrhythmia when using the DL-based CIE approach.Clinical Relevance- Using an arrhythmia-based optimal ECG-lead subset, the classification performance of a deep-learning-based model can be achieved without loss of accuracy in comparison with the full 12-lead set (p<0.05).

Detection of Atrial Fibrillation based on Feature Fusion using Attention-based BiLSTM

Atrial fibrillation (AF) is a common cardiac arrhythmia, and its early detection is crucial for timely treatment. Conventional methods, such as Electrocardiogram (ECG), can be intrusive and require specialized equipment, whereas Photoplethysmography (PPG) offers a non-invasive alternative. In this study, we present a feature fusion approach for AF detection using attention-based Bidirectional Long Short-Term Memory (BiLSTM) and PPG signals. We extract frequency domain (FD) and time domain (TD) features from PPG signals, combine them with deep learning features generated from an attention-based BiLSTM network, and pass the fusion features through a softmax function. Our approach achieves high accuracy (96.5%) and favorable performance metrics (recall 93.20%, precision 94.50%, and F-score 93.09%), improving AF prediction and diagnosis, and providing support for clinicians in their diagnostic processes.

Feasibility, safety and effectiveness of mapping system assisted conduction system pacing: a single-center prospective study

To assess pacing and electrophysiological parameters, as well as mid-term outcomes, among patients undergoing His bundle pacing (HBP) guided by KODEX-EPD (a novel mapping system). Consecutive patients undergoing conduction system pacing (CSP) for bradycardia indications were evaluated. Procedural and fluoroscopic times and pacing characteristics were compared between conventional fluoroscopy (the standard group, N = 20 cases) and KODEX-EPD mapping system guided group (the KODEX group, N = 20cases) at CSP implantation and all patients were followed at 6-month. HBP was achieved in all patients (the standard group 20/20 and the KODEX group 20/20). There was no difference in the mean procedure time between the two groups (63.7 ± 9.3 vs. 78.2 ± 25.1 min, p = 0.33). Compared with the standard group, the KODEX group significantly reduced the intraoperative X-ray exposure time (3.8 ± 0.5 vs. 19.3 ± 5.1 min, p < 0.05) and X-ray dose (23.6 ± 5.4 vs. 120.2 ± 38.3 mGy, p < 0.05). There were no significant differences in atrial impedance (643.0 ± 98.8 vs. 591.5 ± 92.1 Ω, p = 0.09), atrial sensing (2.9 ± 0.8 vs. 2.5 ± 0.8 mV, p = 0.08), ventricular sensing (12.8 ± 2.4 vs. 13.3 ± 3.3 mV, p = 0.63),atrial pacing threshold (1.0 ± 0.2 vs. 1.0 ± 0.1 V/0.4 ms, p = 0.81) and ventricular pacing threshold (1.0 ± 0.2 vs. 0.9 ± 0.1 V/0.4 ms, p = 0.63) between two groups, There were statistical differences in ventricular impedance (640.0 ± 80.3 vs. 702.0 ± 86.1 Ω, p < 0.05). There was no statistical significance in pacing parameters between the two groups at 6 months after procedure (p > 0.05). During the 6-months follow-up period, no adverse events occurred in the two groups. It can be concluded that KODEX-EPD can safely guide His bundle branch pacing lead implantation with reduced fluoroscopic time and dose without lengthening the procedure time.

Beneficial effects of chronic mexiletine treatment in a human model of SCN5A overlap syndrome

AIMS

SCN5A mutations are associated with various cardiac phenotypes, including long QT syndrome type 3 (LQT3), Brugada syndrome (BrS), and cardiac conduction disease (CCD). Certain mutations, such as SCN5A-1795insD, lead to an overlap syndrome, with patients exhibiting both features of BrS/CCD [decreased sodium current (INa)] and LQT3 (increased late INa). The sodium channel blocker mexiletine may acutely decrease LQT3-associated late INa and chronically increase peak INa associated with SCN5A loss-of-function mutations. However, most studies have so far employed heterologous expression systems and high mexiletine concentrations. We here investigated the effects of a therapeutic dose of mexiletine on the mixed phenotype associated with the SCN5A-1795insD mutation in HEK293A cells and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

METHODS AND RESULTS

To assess only the chronic effects on trafficking, HEK293A cells transfected with wild-type (WT) SCN5A or SCN5A-1795insD were incubated for 48 h with 10 µm mexiletine followed by wash-out, which resulted in an increased peak INa for both SCN5A-WT and SCN5A-1795insD and an increased late INa for SCN5A-1795insD. Acute re-exposure of HEK293A cells to 10 µm mexiletine did not impact on peak INa but significantly decreased SCN5A-1795insD late INa. Chronic incubation of SCN5A-1795insD hiPSC-CMs with mexiletine followed by wash-out increased peak INa, action potential (AP) upstroke velocity, and AP duration. Acute re-exposure did not impact on peak INa or AP upstroke velocity, but significantly decreased AP duration.

CONCLUSION

These findings demonstrate for the first time the therapeutic benefit of mexiletine in a human cardiomyocyte model of SCN5A overlap syndrome.

Association Between Intensive vs Standard Blood Pressure Control and Incident Left Ventricular Conduction Disease: A Post Hoc Analysis of the SPRINT Randomized Clinical Trial

Importance

Left ventricular conduction disease predicts heart failure and death, and the only strategies to mitigate its effects involve implantation of a permanent pacemaker. There are currently no proven preventive strategies for this common condition.

Objective

To determine the association between targeting intensive blood pressure (BP) control and the risk of developing left ventricular conduction disease.

Design, Setting, and Participants

This was a post hoc analysis of the 2-arm multicenter Systolic Blood Pressure Intervention Trial (SPRINT), which recruited participants from 102 sites in the US and Puerto Rico and was conducted from November 2010 until August 2015. Adults 50 years and older with hypertension and at least 1 other cardiovascular risk factor were included. Participants with baseline left ventricular conduction disease, ventricular pacing, or ventricular pre-excitation were excluded for the current analysis. Data were analyzed from November 2021 to November 2022.

Intervention

Participants were randomly assigned to a systolic BP target of less than 140 mm Hg (standard treatment group) or less than 120 mm Hg (intensive treatment group).

Main Outcome

The primary outcome was incident left ventricular conduction disease, including any fascicular or left bundle-branch block, assessed by serial electrocardiography. Incident right bundle-branch block was examined as a negative control.

Results

Among 3918 participants randomized to standard treatment and 3956 to intensive treatment (mean [SD] age, 67.6 [9.2] years; 2815 [36%] female) monitored for a median [IQR] 3.5 (0.02-5.2) years, 203 developed left ventricular conduction disease. Older age (hazard ratio per 10-year increase [HR], 1.42; 95% CI, 1.21-1.67; P < .001), male sex (HR, 2.31; 95% CI, 1.63-3.32; P < .001), and cardiovascular disease (HR, 1.46; 95% CI, 1.06-2.00; P = .02) were associated with a higher risk of left ventricular conduction disease. Assignment to intensive treatment was associated with a 26% lower risk of left ventricular conduction disease (HR, 0.74; 95% CI, 0.56-0.98; P = .04). These results persisted when incident ventricular pacing was included in the outcome and when considering all-cause death as a competing risk. In contrast, no association between randomization assignment and right bundle-branch block was observed (HR, 0.95; 95% CI, 0.71-1.27; P = .75).

Conclusions and Relevance

In this study, targeting intensive BP control was associated with lower risk of left ventricular conduction disease in a randomized clinical trial, suggesting that clinically relevant conduction disease may be preventable.

Trial Registration

ClinicalTrials.gov Identifier: NCT01206062.

Cardiovascular imaging in conduction system pacing: What does the clinician need?

Permanent pacemakers are used for symptomatic bradycardia and biventricular pacing (BVP)-cardiac resynchronization therapy (BVP-CRT) is established for heart failure (HF) patients traditionally. According to guidelines, patients' selection for CRT is based on QRS duration (QRSd) and morphology by surface electrocardiogram (ECG). Cardiovascular imaging techniques evaluate cardiac structure and function as well as identify pathophysiological substrate changes including the presence of scar. Cardiovascular imaging helps by improving the selection of candidates, guiding left ventricular (LV) lead placement, and optimization devices during the follow-up. Conduction system pacing (CSP) includes His bundle pacing (HBP) and left bundle branch pacing (LBBP) which is screwed into the interventricular septum. CSP maintains and restores ventricular synchrony in patients with native narrow QRSd and left bundle branch block (LBBB), respectively. LBBP is more feasible than HBP due to a wider target area. This review highlights the role of multimodality cardiovascular imaging including fluoroscopy, echocardiography, cardiac magnetic resonance (CMR), myocardial scintigraphy, and computed tomography (CT) in the pre-procedure assessment for CSP, better selection for CSP candidates, the guidance of CSP lead implantation, and the optimization of devices programming after the procedure. We also compare the different characteristics of multimodality imaging and discuss their potential roles in future CSP implantation.

Optimization of the atrioventricular delay in conduction system pacing

INTRODUCTION

In patients receiving conduction system pacing (CSP), it is not well established how to program the sensed atrioventricular delay (sAVD), with respect to the type of capture obtained (selective, nonselective His-bundle [HB] capture or left bundle branch [LBB] capture). The aim of this study was to acutely assess the effectiveness of an electrophysiology (EP)-guided method for sAVD optimization by comparing it with the echocardiogram-guided optimization.

METHODS AND RESULTS

Consecutive patients undergoing HB or LBB pacing were enrolled. The EP-guided sAVD was defined as the sAVD leading to a PR interval of 150 ms on surface electrocardiogram (ECG). In HB pacing patients, EP-guided sAVD was obtained subtracting the time from the onset of the P wave on ECG to the local atrial electrogram (EGM) recorded by the atrial lead (right atrial sensing latency, RASL) and the His-ventricular interval from 150 ms; in LBB pacing patients, subtracting RASL from 150 ms. Transmitral flow assessment by pulsed wave Doppler was used to find the echo-optimized sAVD by a modified iterative method. The discordance between the EP-guided and the echo-optimized sAVD was recorded.

RESULTS

Seventy-one patients were enrolled: 12 with selective, 32 nonselective HB capture, and 27 LBB capture. Overall, the rate of concordance between the EP-guided and the echo-optimized sAVD was 71.8%, with no significant differences between the three groups.

CONCLUSION

In CSP patients, an optimal sAVD can be programmed, in more than 70% of cases, considering only simple EGM intervals to obtain a physiological PR interval on surface ECG.

Clinical, electrocardiographic, and echocardiographic parameters associated with the development of pacing and implantable cardioverter-defibrillator indication in patients with transthyretin amyloid cardiomyopathy

AIMS

This study aimed to identify factors for attention leading to future pacing device implantation (PDI) and reveal the necessity of prophylactic PDI or implantable cardioverter-defibrillator (ICD) implantation in transthyretin amyloid cardiomyopathy (ATTR-CM) patients.

METHODS AND RESULTS

This retrospective single-center observational study included consecutive 114 wild-type ATTR-CM (ATTRwt-CM) and 50 hereditary ATTR-CM (ATTRv-CM) patients, neither implanted with a pacing device nor fulfilling indications for PDI at diagnosis. As a study outcome, patient backgrounds were compared with and without future PDI, and the incidence of PDI in each conduction disturbance was examined. Furthermore, appropriate ICD therapies were investigated in all 19 patients with ICD implantation. PR-interval ≥220 msec, interventricular septum (IVS) thickness ≥16.9 mm, and bifascicular block were significantly associated with future PDI in ATTRwt-CM patients, and brain natriuretic peptide ≥35.7 pg/mL, IVS thickness ≥11.3 mm, and bifascicular block in ATTRv-CM patients. The incidence of subsequent PDI in patients with bifascicular block at diagnosis was significantly higher than that of normal atrioventricular (AV) conduction in both ATTRwt-CM [hazard ratio (HR): 13.70, P = 0.019] and ATTRv-CM (HR: 12.94, P = 0.002), whereas that of patients with first-degree AV block was neither (ATTRwt-CM: HR: 2.14, P = 0.511, ATTRv-CM: HR: 1.57, P = 0.701). Regarding ICD, only 2 of 16 ATTRwt-CM and 1 of 3 ATTRv-CM patients received appropriate anti-tachycardia pacing or shock therapy, under the number of intervals to detect for ventricular tachycardia of 16-32.

CONCLUSIONS

According to our retrospective single-center observational study, prophylactic PDI did not require first-degree AV block in both ATTRwt-CM and ATTRv-CM patients, and prophylactic ICD implantation was also controversial in both ATTR-CM. Larger prospective, multi-center studies are necessary to confirm these results.

EHRA clinical consensus statement on conduction system pacing implantation: executive summary. Endorsed by the Asia-Pacific Heart Rhythm Society (APHRS), Canadian Heart Rhythm Society (CHRS) and Latin-American Heart Rhythm Society (LAHRS)

Conduction system pacing (CSP) has emerged as a more physiological alternative to right ventricular pacing and is also being used in selected cases for cardiac resynchronization therapy. His bundle pacing was first introduced over two decades ago and its use has risen over the last years with the advent of tools which have facilitated implantation. Left bundle branch area pacing is more recent but its adoption is growing fast due to a wider target area and excellent electrical parameters. Nevertheless, as with any intervention, proper technique is a prerequisite for safe and effective delivery of therapy. This document aims to standardize the procedure and to provide a framework for physicians who wish to start CSP implantation, or who wish to improve their technique. A synopsis is provided in this print edition of EP-Europace. The full document may be consulted online, and a 'Key Messages' App can be downloaded from the EHRA website.

EHRA expert consensus document on the management of arrhythmias in frailty syndrome, endorsed by the Heart Rhythm Society (HRS), Asia Pacific Heart Rhythm Society (APHRS), Latin America Heart Rhythm Society (LAHRS), and Cardiac Arrhythmia Society of Southern Africa (CASSA)

There is an increasing proportion of the general population surviving to old age with significant chronic disease, multi-morbidity, and disability. The prevalence of pre-frail state and frailty syndrome increases exponentially with advancing age and is associated with greater morbidity, disability, hospitalization, institutionalization, mortality, and health care resource use. Frailty represents a global problem, making early identification, evaluation, and treatment to prevent the cascade of events leading from functional decline to disability and death, one of the challenges of geriatric and general medicine. Cardiac arrhythmias are common in advancing age, chronic illness, and frailty and include a broad spectrum of rhythm and conduction abnormalities. However, no systematic studies or recommendations on the management of arrhythmias are available specifically for the elderly and frail population, and the uptake of many effective antiarrhythmic therapies in these patients remains the slowest. This European Heart Rhythm Association (EHRA) consensus document focuses on the biology of frailty, common comorbidities, and methods of assessing frailty, in respect to a specific issue of arrhythmias and conduction disease, provide evidence base advice on the management of arrhythmias in patients with frailty syndrome, and identifies knowledge gaps and directions for future research.

Abnormal Conduction-Induced Cardiomyopathy: JACC Review Topic of the Week

Nonischemic cardiomyopathies are a frequent occurrence. The understanding of the mechanism(s) and triggers of these cardiomyopathies have led to improvement and even recovery of left ventricular function. Although chronic right ventricular pacing-induced cardiomyopathy has been recognized for many years, left bundle branch block and pre-excitation have been recently identified as potential reversible causes of cardiomyopathy. These cardiomyopathies share a similar abnormal ventricular propagation that can be recognized by a wide QRS duration with left bundle branch block pattern; thus, we coined the term abnormal conduction-induced cardiomyopathies. Such abnormal propagation results in an abnormal contractility that can only be recognized by cardiac imaging as ventricular dyssynchrony. Appropriate diagnosis and treatment will not only lead to improved left ventricular ejection fraction and functional class, but may also reduce morbidity and mortality. This review presents an update of the mechanisms, prevalence, incidence, and risk factors, as well as their diagnosis and management, while highlighting current gaps of knowledge.

Lifestyle habits associated with cardiac conduction disease

AIMS

Cardiac conduction disease can lead to syncope, heart failure, and death. The only available therapy is pacemaker implantation, with no established prevention strategies. Research to identify modifiable risk factors has been scant.

METHODS AND RESULTS

Data from the Cardiovascular Health Study, a population-based cohort study of adults ≥ 65 years with annual 12-lead electrocardiograms obtained over 10 years, were utilized to examine relationships between baseline characteristics, including lifestyle habits, and conduction disease. Of 5050 participants (mean age 73 ± 6 years; 52% women), prevalent conduction disease included 257 with first-degree atrioventricular block, 99 with left anterior fascicular block, 9 with left posterior fascicular block, 193 with right bundle branch block (BBB), 76 with left BBB, and 102 with intraventricular block at baseline. After multivariable adjustment, older age, male sex, a larger body mass index, hypertension, and coronary heart disease were associated with a higher prevalence of conduction disease, whereas White race and more physical activity were associated with a lower prevalence. Over a median follow-up on 7 (interquartile range 1-9) years, 1036 developed incident conduction disease. Older age, male sex, a larger BMI, and diabetes were each associated with incident conduction disease. Of lifestyle habits, more physical activity (hazard ratio 0.91, 95% confidence interval 0.84-0.98, P = 0.017) was associated with a reduced risk, while smoking and alcohol did not exhibit a significant association.

CONCLUSION

While some difficult to control comorbidities were associated with conduction disease as expected, a readily modifiable lifestyle factor, physical activity, was associated with a lower risk.

A novel marker to predict cardiac arrhythmia in epilepsy patients: frontal QRS-T angle

OBJECTIVE

The most important complication of epilepsy, which is a chronic disorder of the central nervous system, is sudden unexplained death in epilepsy (SUDEP). The causes of SUDEP are complex and multifactorial. Epilepsy patients are at increased risk of cardiovascular events, SUDEP, and ventricular arrhythmias, due to both the disease itself and the effect of antiseizure medications. Previous studies have commonly focused on cardiac repolarization markers in epilepsy patients. This study aimed to investigate frontal QRS-T angle (FTQ angle), a relatively new repolarization parameter, in epilepsy patients.

PATIENTS AND METHODS

One hundred two epilepsy patients and 86 healthy volunteers as a control group were included in the study. The clinical data of all patients were prospectively recorded during patient visits. All participants underwent 12-lead surface electrocardiography (ECG). SPSS 22 was used to evaluate all data. p<0.05 was considered statistically significant.

RESULTS

When the epilepsy patient group and the control group were compared in terms of QRS (89.59±43.63 vs. 80.00±9.82, p=0.050), QT (364.30±36.16 vs. 335.95±35.64, p<0.001), QTc (418.85±27.06 vs. 409.37±26.66, p=0.018) durations, and FTQ angle (46.55±22.06 vs. 20.84±12.70, p<0.001), statistically significant differences were found between the groups. We observed that FTQ angle was significantly higher in individuals exposed to the disease for more than 10 years (39.2±19.0 vs. 54.7±22.5, p<0.001). In addition, according to the multivariate logistic regression analysis, disease duration was an independent predictor of FTQ angle (β=0.263, p=0.009).

CONCLUSIONS

FTQ angle, a relatively new repolarization parameter, can be used as an inexpensive, easy, reproducible, and reliable ECG marker to predict the risk of adverse cardiac events in epilepsy patients.

Frontier and hotspot evolution in Brugada syndrome: A bibliometric analysis from 2002 to 2022

BACKGROUND

Brugada syndrome (BrS) is a genetic disorder characterized by a typical electrocardiogram pattern and predisposition to arrhythmias and sudden cardiac death. Despite our considerably evolved understanding of BrS, no bibliometrics have been performed in this research field. We aimed to analyze and visualize the characteristics of the scientific outputs, topical evolutions, and research trends of BrS over the past 2 decades using bibliometric analysis.

METHODS

The literature associated with BrS was retrieved from the Science Citation Index Expanded of the Web of Science Core Collection database. Acquired data were then visually analyzed using CiteSpace and VOSviewer.

RESULTS

3042 qualifying records were included in the final analysis. The publication outputs increased over time. The United States was the leading country in the BrS research. The University of Amsterdam (Netherlands) was the most prolific and influential institution. Pedro Brugada, Arthur Wilde, and Charles Antzelevitch exerted notable publication impact and made the most significant contributions in the field of BrS. Heart Rhythm had the highest outputs and Circulation was the most influential journal. Bundle branch block, ST-segment elevation, mechanism, management, right precordial lead, and guideline were the keywords with the strongest citation burst.

CONCLUSION

Research on BrS is prosperous. Keywords and co-citation analysis revealed that the mechanism, diagnosis, risk stratification, and management of BrS were the research hotspots. Besides, the underlying pathophysiology, novel therapies, and personalized risk assessment might be the emerging trends of future research.

Premature atrial contractions promote local directional heterogeneities in conduction velocity vectors

AIMS

Loss of cell-to-cell communication results in local conduction disorders and directional heterogeneity (LDH) in conduction velocity (CV) vectors, which may be unmasked by premature atrial contractions (PACs). We quantified LDH and examined differences between sinus rhythm (SR) and spontaneous PACs in patients with and without atrial fibrillation (AF).

METHODS AND RESULTS

Intra-operative epicardial mapping of the right and left atrium (RA, LA), Bachmann's bundle (BB) and pulmonary vein area (PVA) was performed in 228 patients (54 with AF). Conduction velocity vectors were computed at each electrode using discrete velocity vectors. Directions and magnitudes of individual vectors were compared with surrounding vectors to identify LDH. Five hundred and three PACs [2 (1-3) per patient; prematurity index of 45 ± 12%] were included. During SR, most LDH were found at BB and LA [11.9 (8.3-14.9) % and 11.3 (8.0-15.2) %] and CV was lowest at BB [83.5 (72.4-94.3) cm/s, all P < 0.05]. Compared with SR, the largest increase in LDH during PAC was found at BB and PVA [+13.0 (7.7, 18.3) % and +12.5 (10.8, 14.2) %, P < 0.001]; CV decreased particularly at BB, PVA and LA [-10.0 (-13.2, -6.9) cm/s, -9.3 (-12.5, -6.2) cm/s and -9.1 (-11.7, -6.6) cm/s, P < 0.001]. Comparing patients with and without AF, more LDH were found during SR in AF patients at PVA and BB, although the increase in LDH during PACs was similar for all sites.

CONCLUSION

Local directional heterogeneity is a novel methodology to quantify local heterogeneity in CV as a possible indicator of electropathology. Intra-operative high-resolution mapping indeed revealed that LDH increased during PACs particularly at BB and PVA. Also, patients with AF already have more LDH during SR, which becomes more pronounced during PACs.

Conduction Disturbances and Arrhythmia Risk After Septal Reduction Therapy with Alternative Agents: A Pilot Study with EVOH-DMSO and Systematic Review

OBJECTIVE

Surgical septal myectomy and alcohol septal ablation are recommended treatment modalities for alleviating Left ventricular outflow tract (LVOT) gradient in obstructive HCM. Alcohol septal ablation offers advantages over surgery in many ways. However, it is associated with some life-threatening complications. For this purpose, our center used alternative agents for septal artery embolization. This study compared and evaluated conduction system defects and arrhythmia risk after EVOH-DMSO septal ablation with other alternative agents and alcohol septal ablation.

METHODS

Twenty-five patients who received septal reduction therapy with EVOH-DMSO were analyzed retrospectively, and all non-alcoholic agent's septal ablation studies were systematically reviewed and compared.

RESULTS

Twenty-five patients (52% female; mean age: 55.8 ± 17.1) with symptomatic obstructive HCM were enrolled. The Peak LVOT gradient was significantly reduced after the procedure (68 vs. 20 mmHg; P <0.001). During the 12-month follow-up, no mortality occurred. The complete atrioventricular block was noted in 2 (8%) patients. The incidence of right bundle branch block (RBBB) increased after the procedure (pre-procedural 2 patients (8%), post-procedural 9 patients (36%) P = 0.002). On ECG and Holter monitorization, no sustained ventricular tachyarrhythmia occurred during follow-up, and no change was found in the frequency of atrial fibrillation. We systematically compared EVOH-DMSO to other non-alcohol agents, and we found that EVOH-DMSO can cause conduction system problems more commonly than other non-alcohol agents.

CONCLUSION

EVOH-DMSO could cause conduction system problems more common than other non-alcohol agents but less than alcohol septal ablation.

Activation of small conductance Ca2+ -activated K+ channels suppresses Ca2+ transient and action potential alternans in ventricular myocytes

At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We tested the hypothesis that in single rabbit ventricular myocytes pharmacological modulation of SK channels plays a causative role for the development of pacing-induced CaT and AP duration (APD) alternans. SK channel blockers (apamin, UCL1684) had only a minor effect on AP repolarization. However, SK channel activation by NS309 resulted in significant APD shortening, demonstrating that functional SK channels are well expressed in ventricular myocytes. The effects of NS309 were prevented or reversed by apamin and UCL1684, indicating that NS309 acted on SK channels. SK channel activation abolished or reduced the degree of pacing-induced CaT and APD alternans. Inhibition of KV 7.1 (with HMR1556) and KV 11.1 (with E4031) channels was used to mimic conditions of long QT syndromes type-1 and type-2, respectively. Both HMR1556 and E4031 enhanced CaT alternans that was prevented by SK channel activation. In AP voltage-clamped cells the SK channel activator had no effect on CaT alternans, confirming that suppression of CaT alternans was caused by APD shortening. APD shortening contributed to protection from alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest that SK activation could be a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy for patients with long QT syndrome. KEY POINTS: At the cellular level, cardiac alternans is observed as beat-to-beat alternations in contraction strength, action potential (AP) morphology and intracellular Ca2+ release amplitude, and is a risk factor for cardiac arrhythmia. The (patho)physiological roles of small conductance Ca2+ -activated K+ (SK) channels in ventricles are poorly understood. We investigated whether pharmacological modulation of SK channels affects the development of cardiac alternans in normal ventricular cells and in cells with drug-induced long QT syndrome (LQTS). While SK channel blockers have only a minor effect on AP morphology, their activation leads to AP shortening and abolishes or reduces the degree of pacing-induced Ca2+ and AP alternans. AP shortening contributed to protection against alternans by lowering sarcoplasmic reticulum Ca2+ content and curtailing Ca2+ release. The data suggest SK activation as a potential intervention to avert the development of alternans with important ramifications for arrhythmia prevention for patients with LQTS.

When the Gates Swing Open Only: Arrhythmia Mutations That Target the Fast Inactivation Gate of Nav1.5

Na_v1.5 is the main voltage-gated sodium channel found in cardiac muscle, where it facilitates the fast influx of Na⁺ ions across the cell membrane, resulting in the fast depolarization phase-phase 0 of the cardiac action potential. As a result, it plays a major role in determining the amplitude and the upstroke velocity of the cardiac impulse. Quantitively, cardiac sodium channel activates in less than a millisecond to trigger the cardiac action potential and inactivates within 2-3 ms to facilitate repolarization and return to the resting state in preparation for firing the next action potential. Missense mutations in the gene that encodes Na_v1.5 (SCN5A), change these time constants which leads to a wide spectrum of cardiac diseases ranging from long QT syndrome type 3 (LQT3) to sudden cardiac death. In this mini-review I will focus on the missense mutations in the inactivation gate of Na_v1.5 that results in arrhythmia, attempting to correlate the location of the missense mutation to their specific phenotype.

Conduction System Pacing Versus Conventional Cardiac Resynchronization Therapy in Congenital Heart Disease

BACKGROUND

Dyssynchrony-associated left ventricular systolic dysfunction is a major contributor to heart failure in congenital heart disease (CHD). Although conventional cardiac resynchronization therapy (CRT) has shown benefit, the comparative efficacy of cardiac conduction system pacing (CSP) is unknown.

OBJECTIVES

To compare the clinical outcomes of CSP vs conventional CRT in CHD with biventricular, systemic left ventricular anatomy.

METHODS

Retrospective CSP data from 7 centers were compared with propensity score-matched conventional CRT control subjects. Outcomes were lead performance, change in left ventricular ejection fraction (LVEF), and QRS duration at 12 months.

RESULTS

A total of 65 CSP cases were identified (mean age 37 ± 21 years, 46% men). The most common CHDs were tetralogy of Fallot (n = 12 [19%]) and ventricular septal defect (n = 12 [19%]). CSP was achieved after a mean of 2.5 ± 1.6 attempts per procedure (38 patients with left bundle branch pacing, 17 with HBP, 10 with left ventricular septal myocardial). Left bundle branch area pacing [LBBAP] vs HBP was associated with a smaller increase in pacing threshold (Δ pacing threshold 0.2 V vs 0.8 V; P = 0.05) and similar sensing parameters at follow-up. For 25 CSP cases and control subjects with baseline left ventricular systolic dysfunction, improvement in LVEF was non-inferior (Δ LVEF 9.0% vs 6.0%; P = 0.3; 95% confidence limits: -2.9% to 10.0%) and narrowing of QRS duration was more pronounced for CSP (Δ QRS duration 35 ms vs 14 ms; P = 0.04). Complications were similar (3 [12%] CSP, 4 [16%] conventional CRT; P = 1.00).

CONCLUSIONS

CSP can be reliably achieved in biventricular, systemic left ventricular CHD patients with similar improvement in LVEF and greater QRS narrowing for CSP vs conventional CRT at 1 year. Among CSP patients, pacing electrical parameters were superior for LBBAP vs HBP.

Arrhythmogenic Cardiomyopathy: Exercise Pitfalls, Role of Connexin-43, and Moving beyond Antiarrhythmics

Arrhythmogenic Cardiomyopathy (ACM), a Mendelian disorder that can affect both left and right ventricles, is most often associated with pathogenic desmosomal variants that can lead to fibrofatty replacement of the myocardium, a pathological hallmark of this disease. Current therapies are aimed to prevent the worsening of disease phenotypes and sudden cardiac death (SCD). Despite the use of implantable cardioverter defibrillators (ICDs) there is no present therapy that would mitigate the loss in electrical signal and propagation by these fibrofatty barriers. Recent studies have shown the influence of forced vs. voluntary exercise in a variety of healthy and diseased mice; more specifically, that exercised mice show increased Connexin-43 (Cx43) expression levels. Fascinatingly, increased Cx43 expression ameliorated the abnormal electrical signal conduction in the myocardium of diseased mice. These findings point to a major translational pitfall in current therapeutics for ACM patients, who are advised to completely cease exercising and already demonstrate reduced Cx43 levels at the myocyte intercalated disc. Considering cardiac dysfunction in ACM arises from the loss of cardiomyocytes and electrical signal conduction abnormalities, an increase in Cx43 expression-promoted by low to moderate intensity exercise and/or gene therapy-could very well improve cardiac function in ACM patients.

Investigation of the Evolution of Wavelet Higher-Order Dynamics in Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with significant morbidity and mortality. Owing to the advances in sensor technology and the emergence of wearable devices that enable daily self-monitoring, ECG signal processing methods for the automatic detection of AF are more pertinent than ever. In this paper, we investigate the use of wavelet higher-order statistics (WHOS) for feature extraction and differentiation between normal sinus rhythm and AF. The proposed approach captures the evolution of the WHOS dynamics and quantifies the changes in the time-varying characteristics of the frequency couplings caused by AF. Results obtained from the statistical analysis of a dataset of 5834 single-lead ECG recordings, reveal 46/50 statistically significant features and provide insight into the complexity of the evolution of the ECG non-linearities during AF.

Conduction system pacing in prosthetic heart valves

BACKGROUND

There has been increasing interest in physiologic pacing techniques that directly activate the specialized conduction system. We aimed to assess outcomes of conduction system pacing (CSP) in patients with prosthetic heart valves.

METHODS

This systematic review was performed according to PRISMA guidelines. Freeman-Tukey double arcsine transformation with the random-effect model was used to summarize the data. Outcomes studied were 1) implant success (defined as ability to recruit the His-Purkinje system or the distal Purkinje system); (2) lead parameters at implant and follow-up; and (3) procedure-related complications.

RESULTS

This systematic review of 7 studies included 267 unique patients in whom CSP was attempted with either HBP or LBBAP for pacing indications after a prosthetic valve. HBP was attempted in 38% (n = 108), while LBBAP in 62% (n = 175) patients. The overall success rate of CSP was 87%, while in patients post-TAVR, the overall success rate was 83.2%. In the subgroup analysis, LBBAP had a significant higher overall success rate compared to HBP (94.3% vs. 76.5%, p _interaction = 0.02) and post-TAVR patients (94.3 vs. 66.9%, p _interaction < 0.01), respectively. The LBBAP thresholds were significantly lower compared to HBP both at implant (0.67 ± 0.4 @ 0.44 ms vs. 1.35 ± 1 @ 0.85 ms, p _interaction < 0.01) and at a mean follow-up of 12.4 ± 8 months (0.73 ± 0.1 @ 0.44 ms vs. 1.39 ± 1 @ 0.85 ms, p _interaction < 0.01), respectively.

CONCLUSION

CSP is safe and feasible in patients with a prosthetic valve, with a significantly higher success rate and superior lead parameters with LBBAP than HBP, especially in patients post-TAVR.

The Effect of Medication on P-wave Beat-to-Beat Variability in Atrial Fibrillation during Sinus Rhythm

Atrial Fibrillation (AF) is the most common cardiac arrhythmia, and its progressive nature is associated with gradual atrial remodeling. The P-wave in the surface Electrocardiogram (ECG) reflects the atrial activation, while the modification of the atrial pathophysiological properties leads to P-wave morphology (PWM) alternations. In paroxysmal AF (pAF), the modifications of the PWM may have a spontaneous rather than permanent presence in the ECG signal. The analysis of the P-waves, during sinus rhythm, on a beat-to-beat basis, has revealed the existence of at least two PWM. In addition, the wavelet characteristics of the P-wave matching the main morphology can accurately distinguish the patients with pAF from healthy volunteers. In this work, we examine the hypothesis that there is an effect of the anti-arrhythmic medication on beat-to-beat PWM alternations of pAF patients. ECG signals of high frequency (1000Hz), in the three orthogonal leads, were collected for 81 pAF patients of minimal and mild AF burden, 47 of which receiving antiarrhythmic medication treatment, and from 56 healthy volunteers. Kruskal-Wallis test was performed, and the preliminary results denote the existence of statistically significant differences between the groups. A 3-class Random Forest classifier was trained, using the forward wrapper approach, resulting in a high overall classification performance (AUC = 85.75%). This analysis is a step towards improving understanding of medication effect on the variability of P-wave.Clinical Relevance- The methodology presented in this paper can be used to perform a non-invasive characterization of low burden pAF patients using the ECG recording.

Disturbances in the intraventricular conduction system in teenagers with type 1 diabetes. A pilot study

Body Surface Potential Mapping (BSPM) is a multi-electrode synchronous method for examining electrocardiographic records on the patients' body surface that allows the assessment of changes in the heart conduction system. The aim of the study was to visualize and evaluate changes in the intraventricular system in adolescents with T1D.

PATIENTS AND METHODS

Inclusion criteria: age > 12 years, T1D duration >3 years, HbA1c >8%.

EXCLUSION CRITERIA

diagnosis of autonomic neuropathy, heart structural defects, heart failure. BSPM data were processed into map plotting to illustrate differences in ventricular activation time (VAT, isochron lines).

RESULTS

33 teenagers (20 boys), mean age 15.0 ± 2.1 years, T1D from 6.8 ± 4.1 years were included. Mean HbA1c was 9.6 ± 2.0%. In the standard ECG recording abnormalities were not present. The distribution of isolines on the group-mean map plotted for T1D patients only initially resembles the course of isolines on the group-map for normal subjects (N = 30), in whom the electrical impulse stimulating the heart ventricles passes through the atrio-ventricular node, then symmetrically excites the branches of His bundle and finally the Purkinje fibers. In T1D patients, after proper onset of intraventricular stimulation, the isolines reflecting the both ventricles reach higher time values, which indicates problems in the propagation of the ventricular depolarization.