Epidemiology of sudden cardiac death: clinical and research implications

Development of an algorithm to guide management of cardiorespiratory arrest in a diving bell

Aim

The management of cardiorespiratory arrest in a diving bell presents multiple clinical, technical, and environmental considerations that standard resuscitation algorithms do not address, and no situation-specific algorithm exists. The development and testing of an algorithm to guide the management of cardiorespiratory arrest in a bell is described.

Methods

An iterative approach to algorithm development was used. Phase 1 involved a small multidisciplinary group and took place in a simulation centre and a decommissioned diving bell. The algorithm was then refined in a purpose-build simulation complex with repeated simulation by a group of divers, and with input from industry experts. ALS principles were followed unless contextual or technical factors necessitated deviation.

Results

Clinical and technical aspects of the resuscitation are addressed. Key priorities that conflict with standard ALS principles are: prioritisation of rescue breaths; use of mechanical CPR when available; and the provision of CPR with the casualty in a seated position where necessary.

Conclusion

This is the first algorithm to guide the delivery of resuscitation in a diving bell. It incorporates adapted ALS principles and available data concerning compression technique effectiveness, and was informed by industry and clinical expertise. It provides guiding principles that can be adapted to setting-specific needs, and we would encourage its industry-wide international adoption.

Performance of postmortem CT in the diagnosis of natural death from out-of-hospital cardiac arrest

PURPOSE

Postmortem CT (PMCT) is used widely to identify the cause of death. However, its diagnostic performance in cases of natural death from out-of-hospital cardiac arrest (OHCA) may be unsatisfactory because the cause tends to be cardiogenic and cannot be detected on PMCT images. We retrospectively investigated the diagnostic performance of PMCT in the diagnosis of natural death from OHCA and compared it to that of unnatural death.

MATERIALS AND METHODS

Our series included 450 cases; 336 were natural- and 114 were unnatural death cases. Between 2018 and 2022 all underwent non-contrast PMCT to identify the cause of death. Two radiologists reviewed the PMCT images and categorized them as diagnostic (PMCT alone sufficient to determine the cause of death), suggestive (the cause of death was suggested but additional information was needed), and non-diagnostic (the cause of death could not be determined on PMCT images). The diagnostic performance of PMCT was defined by the percentage of diagnosable and suggestive cases and compared between natural- and unnatural death cases. Interobserver agreement for the cause of death on PMCT images was also assessed with the Cohen kappa coefficient of concordance.

RESULTS

The diagnostic performance of PMCT for the cause of natural- and unnatural deaths from OHCA was 30.3% and 66.6%, respectively (p < 0.01). The interobserver agreement for the cause of natural- and unnatural deaths on PMCT images was very good with kappa value 0.92 and 0.96, respectively.

CONCLUSION

As PMCT identified the cause of natural death by OHCA in only 30% of cases, its diagnostic performance must be improved.

Obesity Arrhythmias: Role of IL-6 Trans-Signaling

Obesity is a chronic disease that is rapidly increasing in prevalence and affects more than 600 million adults worldwide, and this figure is estimated to increase by at least double by 2030. In the United States, more than one-third of the adult population is either overweight or obese. The global obesity epidemic is a major risk factor for the development of life-threatening arrhythmias occurring in patients with long QT, particularly in conditions where multiple heart-rate-corrected QT-interval-prolonging mechanisms are simultaneously present. In obesity, excess dietary fat in adipose tissue stimulates the release of immunomodulatory cytokines such as interleukin (IL)-6, leading to a state of chronic inflammation in patients. Over the last decade, increasing evidence has been found to support IL-6 signaling as a powerful predictor of the severity of heart diseases and increased risk for ventricular arrhythmias. IL-6's pro-inflammatory effects are mediated via trans-signaling and may represent a novel arrhythmogenic risk factor in obese hearts. The first selective inhibitor of IL-6 trans-signaling, olamkicept, has shown encouraging results in phase II clinical studies for inflammatory bowel disease. Nevertheless, the connection between IL-6 trans-signaling and obesity-linked ventricular arrhythmias remains unexplored. Therefore, understanding how IL-6 trans-signaling elicits a cellular pro-arrhythmic phenotype and its use as an anti-arrhythmic target in a model of obesity remain unmet clinical needs.

"Re-evaluation of variants of uncertain significance in patients with hereditary arrhythmogenic disorders"

BACKGROUND

Genetic diagnostics support the diagnosis of hereditary arrhythmogenic diseases, but variants of uncertain significance (VUS) complicate matters, emphasising the need for regular reassessment. Our study aims to reanalyse rare variants in different genes in order to decrease VUS diagnoses and thus improve risk stratification and personalized treatment for patients with arrhythmogenic disorders.

METHODS

Genomic DNA was analysed using Sanger sequencing and next-generation sequencing (NGS). The Data was evaluated using various databases and in silico prediction tools and classified according to current ACMG standards by two independent experts.

RESULTS

We identified 53 VUS in 30 genes, of which 17 variants (32%) were reclassified. 13% each were downgraded to likely benign (LB) and benign (B) and 6% were upgraded to likely pathogenic (LP). Reclassifications mainly occurred among variants initially classified in 2017-2019, with rates ranging from 50 to 60%.

CONCLUSION

The results support the assumption that regular reclassification of VUS is important, as it provides new insights for genetic diagnostics, that benefit patients and guide therapeutic approach.

The Lived Experience of Cardiac Arrest Survivors: A Scoping Review

BACKGROUND

Survival rates after cardiac arrest have steadily increased over the past few decades because of the adoption of cardiopulmonary resuscitation, public access to automated external defibrillators, and an increase in public education on how to perform cardiopulmonary resuscitation. The lived experiences of post-cardiac arrest survival have been underexplored. The themes that resulted from the analysis in this scoping review can inform clinical practice and propose strategies to improve the patients' quality of life.

OBJECTIVE

The objective of this scoping review was to map out qualitative literature that explores the lived experience of individuals who have survived cardiac arrest.

METHOD

In this scoping review, the authors examined peer-reviewed qualitative studies identified in the PubMed, CINAHL, and MEDLINE databases. Arksey and O'Malley's methodological framework for conducting a scoping study was followed.

RESULTS

The search yielded 174 articles, with 16 meeting inclusion criteria for this scoping review. Initially, 14 articles were selected, and 2 additional articles were identified through references. Themes extracted from these 16 articles include the need for support and information, emotional challenges, and acceptance of a new reality.

CONCLUSION

Cardiac arrest survivors often experience loss of control, vulnerability, and insecurity. These emotional changes can be significant and may include physical challenges, cognitive impairments, and psychological distress, which can cause individuals to reevaluate their perspectives on life and accept a new reality, potentially leading to changes in their future outlook.

International Criteria for Reporting Study Quality for Sudden Cardiac Arrest/Death Tool

BACKGROUND

Studies reporting on the incidence of sudden cardiac arrest and/or death (SCA/D) in athletes commonly lack methodological and reporting rigor, which has implications for screening and preventative policy in sport. To date, there are no tools designed for assessing study quality in studies investigating the incidence of SCA/D in athletes.

METHODS AND RESULTS

The International Criteria for Reporting Study Quality for Sudden Cardiac Arrest/Death tool (IQ-SCA/D) was developed following a Delphi process. Sixteen international experts in sports cardiology were identified and invited. Experts voted on each domain with subsequent moderated discussion for successive rounds until consensus was reached for a final tool. Interobserver agreement between a novice, intermediate, and expert observer was then assessed from the scoring of 22 relevant studies using weighted and unweighted κ analyses. The final IQ-SCA/D tool comprises 8 domains with a summated score of a possible 22. Studies are categorized as low, intermediate, and high quality with summated IQ-SCA/D scores of ≤11, 12 to 16, and ≥17, respectively. Interrater agreement was "substantial" between all 3 observers for summated IQ-SCA/D scores and study categorization.

CONCLUSIONS

The IQ-SCA/D is an expert consensus tool for assessing the study quality of research reporting the incidence of SCA/D in athletes. This tool may be used to assist researchers, reviewers, journal editors, and readers in contextualizing the methodological quality of different studies with varying athlete SCA/D incidence estimates. Importantly, the IQ-SCA/D also provides an expert-informed framework to support and guide appropriate design and reporting practices in future SCA/D incidence trials.

Molecular genetic screening after non-ischaemic sudden cardiac arrest and no overt cardiomyopathy in real life: A major tool for the aetiological diagnostic work-up

BACKGROUND

With the development of advanced sequencing techniques, genetic testing has emerged as a valuable tool for the work-up of non-ischaemic sudden cardiac arrest (SCA).

AIMS

To evaluate the effectiveness of genetic testing in patients with unexplained SCA, according to clinical phenotype.

METHODS

All patients who underwent molecular genetic testing for non-ischaemic SCA with no left ventricular cardiomyopathy between 2012 and 2021 in two French university hospitals were included.

RESULTS

Of 66 patients (mean age 36.7±11.9years, 54.5% men), 21 (31.8%; 95% confidence interval 22.4-45.3%) carried a genetic variant: eight (12.1%) had a pathogenic or likely pathogenic (P/LP) variant and 13 (19.7%) had a variant of uncertain significance (VUS). Among 37 patients (56.1%) with no phenotypic clues, genetic testing identified a P/LP variant in five (13.5%), mainly in RYR2 (n=3) and SCN5A (n=2), and a VUS in nine (24.3%). None of the nine patients with phenotypic evidence of channelopathies had P/LP variants, but two had VUS in RYR2 and NKX2.5. Among the 20 patients with suspected arrhythmogenic cardiomyopathy, three P/LP variants (15.0%) and two VUS (10.0%) were found in DSC2, PKP2, SCN5A and DSG2, TRPM4, respectively. Genetic testing was performed sooner after cardiac arrest (P<0.001) and results were obtained more rapidly (P=0.02) after versus before 2016.

CONCLUSION

This study highlights the utility of molecular genetic testing with a genetic variant of interest identified in one-third of patients with unexplained SCA. Genetic testing was beneficial even in patients without phenotypic clues, with one-fourth of patients carrying a P/LP variant that could have direct implications.

Feasibility of remote monitoring for fatal coronary heart disease using Apple Watch ECGs

Background

Fatal coronary heart disease (FCHD) is often described as sudden cardiac death (affects >4 million people/year), where coronary artery disease is the only identified condition. Electrocardiographic artificial intelligence (ECG-AI) models for FCHD risk prediction using ECG data from wearable devices could enable wider screening/monitoring efforts.

Objectives

To develop a single-lead ECG-based deep learning model for FCHD risk prediction and assess concordance between clinical and Apple Watch ECGs.

Methods

An FCHD single-lead ("lead I" from 12-lead ECGs) ECG-AI model was developed using 167,662 ECGs (50,132 patients) from the University of Tennessee Health Sciences Center. Eighty percent of the data (5-fold cross-validation) was used for training and 20% as a holdout. Cox proportional hazards (CPH) models incorporating ECG-AI predictions with age, sex, and race were also developed. The models were tested on paired clinical single-lead and Apple Watch ECGs from 243 St. Jude Lifetime Cohort Study participants. The correlation and concordance of the predictions were assessed using Pearson correlation (R), Spearman correlation (ρ), and Cohen's kappa.

Results

The ECG-AI and CPH models resulted in AUC = 0.76 and 0.79, respectively, on the 20% holdout and AUC = 0.85 and 0.87 on the Atrium Health Wake Forest Baptist external validation data. There was moderate-strong positive correlation between predictions (R = 0.74, ρ = 0.67, and κ = 0.58) when tested on the 243 paired ECGs. The clinical (lead I) and Apple Watch predictions led to the same low/high-risk FCHD classification for 99% of the participants. CPH prediction correlation resulted in an R = 0.81, ρ = 0.76, and κ = 0.78.

Conclusion

Risk of FCHD can be predicted from single-lead ECGs obtained from wearable devices and are statistically concordant with lead I of a 12-lead ECG.

Viral myocarditis in combination with genetic cardiomyopathy as a cause of sudden death. An autopsy series

Sudden cardiac death (SCD) is a major public health issue worldwide. In the young (< 40 years of age), genetic cardiomyopathies and viral myocarditis, sometimes in combination, are the most frequent, but underestimated, causes of SCD. Molecular autopsy is essential for prevention. Several studies have shown an association between genetic cardiomyopathies and viral myocarditis, which is probably underestimated due to insufficient post-mortem investigations. We report on four autopsy cases illustrating the pathogenesis of these combined pathologies. In two cases, a genetic hypertrophic cardiomyopathy was diagnosed in combination with Herpes Virus Type 6 (HHV6) and/or Parvovirus-B19 (PVB19) in the heart. In the third case, autopsy revealed a dilated cardiomyopathy and virological analyses revealed acute myocarditis caused by three viruses: PVB19, HHV6 and Epstein-Barr virus. Genetic analyses revealed a mutation in the gene coding for desmin. The fourth case illustrated a channelopathy and a PVB19/HHV6 coinfection. Our four cases illustrate the highly probable deleterious role of cardiotropic viruses in the occurrence of SCD in subjects with genetic cardiomyopathies. We discuss the pathogenetic link between viral myocarditis and genetic cardiomyopathy. Molecular autopsy is essential in prevention of these SCD, and a close collaboration between cardiologists, pathologists, microbiologists and geneticians is mandatory.

Sudden Cardiac Death, Post-Mortem Investigation: A Proposing Panel of First Line and Second Line Genetic Tests

Investigating the causes of Sudden cardiac death (SCD) is always difficult; in fact, genetic cardiac conditions associated with SCD could be "silent" even during autopsy investigation. In these cases, it is important to exclude other aetiology and assist to ask for genetic investigations. Herein, the purpose of this review is to collect the most-implicated genes in SCD and generate a panel with indications for first line and second line investigations. A systematic review of genetic disorders that may cause SCD in the general population was carried out according to the Preferred Reporting Item for Systematic Review (PRISMA) standards. We subsequently listed the genes that may be tested in the case of sudden cardiac death when the autopsy results are negative or with no evidence of acquired cardiac conditions. To make genetic tests more specific and efficient, it is useful and demanded to corroborate autopsy findings with the molecular investigation as evident in the panel proposed. The genes for first line investigations are HCM, MYBPC3, MYH7, TNNT2, TNNI3, while in case of DCM, the most implicated genes are LMNA and TTN, and in second line for these CDM, ACTN2, TPM1, C1QPB could be investigated. In cases of ACM/ARVC, the molecular investigation includes DSP, DSG2, DSC2, RYR2, PKP2. The channelopathies are associated with the following genes: SCN5A, KCNQ1, KCNH2, KCNE1, RYR2. Our work underlines the importance of genetic tests in forensic medicine and clinical pathology; moreover, it could be helpful not only to assist the pathologists to reach a diagnosis, but also to prevent other cases of SCD in the family of the descendant and to standardise the type of analysis performed in similar cases worldwide.

Exploring the Full Potential of Radiofrequency Technology: A Practical Guide to Advanced Radiofrequency Ablation for Complex Ventricular Arrhythmias

PURPOSE OF REVIEW

Percutaneous radiofrequency (RF) catheter ablation is an established strategy to prevent ventricular tachycardia (VT) recurrence and ICD shocks. Yet delivery of durable lesion sets by means of traditional unipolar radiofrequency ablation remains challenging, and left ventricular transmurality is rarely achieved. Failure to ablate and eliminate functionally relevant areas is particularly common in deep intramyocardial substrates, e.g. septal VT and cardiomyopathies. Here, we aim to give a practical-orientated overview of advanced and emerging RF ablation technologies to target these complex VT substrates. We summarize recent evidence in support of these technologies and share experiences from a tertiary VT centre to highlight important "hands-on" considerations for operators new to advanced RF ablation strategies.

RECENT FINDINGS

A number of innovative and modified radiofrequency ablation approaches have been proposed to increase energy delivery to the myocardium and maximize RF lesion dimensions and depth. These include measures of impedance modulation, combinations of simultaneous unipolar ablations or true bipolar ablation, intramyocardial RF delivery via wires or extendable RF needles and investigational linear or spherical catheter designs. Recent new clinical evidence for the efficacy and safety of these investigational technologies and strategies merits a re-evaluation of their role and clinic application for percutaneous VT ablations. Complexity of substrates targeted with percutaneous VT ablation is increasing and requires detailed preprocedural imaging to characterize the substrate to inform the procedural approach and selection of ablation technology. Depending on local experience, options for additional and/or complementary interventional treatments should be considered upfront in challenging substrates to improve the success rates of index procedures. Advanced RF technologies available for clinical VT ablations include impedance modulation via hypotonic irrigation or additional dispersive patches and simultaneous unipolar as well as true bipolar ablation. Promising investigational RF technologies involve an extendable needle RF catheter, intramyocardial RF delivery over intentionally perforated wires as well as a variety of innovative ablation catheter designs including multipolar linear, spherical and partially insulated ablation catheters.

Risk Prediction for Sudden Cardiac Death in the General Population: A Systematic Review and Meta-Analysis

Objective: Identification of SCD risk is important in the general population from a public health perspective. The objective is to summarize and appraise the available prediction models for the risk of SCD among the general population. Methods: Data were obtained searching six electronic databases and reporting prediction models of SCD risk in the general population. Studies with duplicate cohorts and missing information were excluded from the meta-analysis. Results: Out of 8,407 studies identified, fifteen studies were included in the systematic review, while five studies were included in the meta-analysis. The Cox proportional hazards model was used in thirteen studies (96.67%). Study locations were limited to Europe and the United States. Our pooled meta-analyses included four predictors: diabetes mellitus (ES = 2.69, 95%CI: 1.93, 3.76), QRS duration (ES = 1.16, 95%CI: 1.06, 1.26), spatial QRS-T angle (ES = 1.46, 95%CI: 1.27, 1.69) and factional shortening (ES = 1.37, 95%CI: 1.15, 1.64). Conclusion: Risk prediction model may be useful as an adjunct for risk stratification strategies for SCD in the general population. Further studies among people except for white participants and more accessible factors are necessary to explore.

Ankle-Brachial Index and Risk of Sudden Cardiac Death in the Community: The ARIC Study

BACKGROUND

Sudden cardiac death (SCD) is a significant global public health problem accounting for 15% to 20% of all deaths. A great majority of SCD is associated with coronary heart disease, which may first be detected at autopsy. The ankle-brachial index (ABI) is a simple, noninvasive measure of subclinical atherosclerosis. The purpose of this study was to examine the relationship between ABI and SCD in a middle-aged biracial general population.

METHODS AND RESULTS

Participants of the ARIC (Atherosclerosis Risk in Communities) study with an ABI measurement between 1987 and 1989 were included. ABI was categorized as low (≤0.90), borderline (0.90-1.00), normal (1.00-1.40), and noncompressible (>1.40). SCD was defined as a sudden pulseless condition presumed to be caused by a ventricular tachyarrhythmia in a previously stable individual and was adjudicated by a committee of cardiac electrophysiologists, cardiologists, and internists. Cox proportional hazards models were used to evaluate the associations between baseline ABI and incident SCD. Of the 15 081 participants followed for a median of 23.5 years, 556 (3.7%) developed SCD (1.96 cases per 1000 person-years). Low and borderline ABIs were associated with an increased risk of SCD (demographically adjusted hazard ratios [HRs], 2.27 [95% CI, 1.64-3.14] and 1.52 [95% CI, 1.17-1.96], respectively) compared with normal ABI. The association between low ABI and SCD remained significant after adjustment for traditional cardiovascular risk factors (HR, 1.63 [95% CI, 1.15-2.32]).

CONCLUSIONS

Low ABI is independently associated with an increased risk of SCD in a middle-aged biracial general population. ABI could be incorporated into future SCD risk prediction models.

The barriers and facilitators to initiation of telephone-assisted bystander cardiopulmonary resuscitation for patients experiencing out-of-hospital cardiac arrest in a private emergency dispatch centre in South Africa

Background

The incidence of cardiovascular diseases, and with it out-of-hospital cardiac arrest (OHCA), is on the increase in low- to middle-income countries (LMICs), like South Africa. Interventions such as mass public cardiopulmonary resuscitation (CPR) training campaigns and public access defibrillators are expensive and out of reach for many LMICs. Telephone-assisted CPR (tCPR) is a cost-effective, scalable alternative. This study explored the barriers and facilitators to tCPR uptake in OHCA in a private South African emergency dispatch centre.

Methods

This qualitative study applied inductive dominant content analysis to emergency call recordings of OHCA cases into a private emergency dispatch centre. Calls were analysed to the latent level to identify barriers and facilitators. Cases were sampled randomly, until data saturation.

Results

Saturation occurred after the analysis of 25 recordings. A further three recordings were analysed to confirm saturation of the facilitators; yielding a final sample size of 28 calls. Overall, t-CPR was offered in 23 (82.1%) cases, but only initiated in 8 (34.8%) of these calls. Five barriers ("Poor Communication"; "Lack of Support"; "Caller Hesitance or Uncertainty;" "Emotionality"; and "Practical Barriers") and three facilitators ("Caller Willingness"; "Support" and "CPR in Progress") were extracted.

Conclusion

Numerous barriers limit the initiation of tCPR in the South African private sector EMS. It is crucial to address these barriers and leverage the facilitators in order to improve tCPR uptake. This study highlights the importance of using specific language techniques and developing tailored tCPR algorithms to overcome these barriers, which is underpinned by standardised training of call-takers.

Incidence of Sudden Cardiac Death in Low- and Middle-Income Countries: A Systematic Review of Cohort Studies

Sudden cardiac death (SCD) is a leading cause of mortality worldwide and, in recent years, has become an urgent public health concern in low- and middle-income countries (LMICs). Data from LMICs, however, remains limited. As such, the aim of this article is to systematically review the current literature on the incidence of SCD in LMICs to inform policymakers and identify potential research gaps. A search of PubMed and Embase was utilized to capture the targeted condition, outcome, and setting. Only peer-reviewed cohort studies in LMICs reporting SCD incidence estimates in the general population of individuals aged ≥1 year were eligible for selection. Papers providing incidence data for specific types of SCD, including sudden coronary death or death from sudden cardiac arrest, were also included. After deduplication, 1941 citations were identified and screened. Seven studies representing four countries-Cameroon, China, India, and Iran-met the criteria for inclusion and were considered in our analysis. The crude incidence rate for SCD ranged from 19.9 to 190 cases per 100,000 person-years, while age-adjusted rates ranged from 33.6 to 230 cases per 100,000 person-years. There was notable variability in methods utilized to ascertain SCD cases. These findings suggest that the incidence of all-cause SCD in LMICs and may exceed that of high-income countries; however, observed disparities may be partly attributable to differences in case ascertainment methods. Additional research is needed to better understand the true incidence of SCD in developing countries. It is crucial that future studies across regions utilize standard diagnostic criteria and methodology for identifying SCD, which would provide a framework by which to compare outcomes between settings.

Circulating noradrenaline leads to release of neuropeptide Y from cardiac sympathetic nerve terminals via activation of β-adrenergic receptors

Cardiac disease is marked by sympathoexcitation and elevated levels of noradrenaline (NA) and cotransmitter neuropeptide Y (NPY). Increased NPY levels are associated with a greater risk of ventricular arrhythmias and mortality. Nonetheless, the factors that cause NPY release remain poorly understood. We hypothesized that circulating catecholamines might lead to NPY release from myocardial sympathetic nerve terminals via a β-receptor-mediated mechanism that enhances sympathoexcitation. Ventricular interstitial NA and NPY levels were measured in six Yorkshire pigs after i.v. administration of NA (1 mg) and before and after propranolol infusion (1 mg/kg). Real-time interstitial NPY levels were measured using ventricular capacitive immunoprobes (CIs) affixed with NPY antibodies and quantified as the change in CI input current (INPY ) upon binding of NPY. Interstitial NA was measured with adjacent fast-scan cyclic voltammetry probes (INA ). A left ventricular pressure catheter and continuous ECGs were used for haemodynamic recordings, and an epicardial 56-electrode sock was used for measurements of activation recovery interval, a surrogate of action potential duration. Upon administration of NA, heart rate and left ventricular pressure increased, and activation recovery interval shortened. Notably, NA significantly increased interstitial myocardial NPY levels. After propranolol, changes in heart rate and activation recovery interval were largely mitigated. The INA increased to a similar extent post-propranolol vs. pre-propranolol, but changes in INPY were significantly reduced post-propranolol. Coronary sinus plasma analyses confirmed fast-scan cyclic voltammetry and CI findings. Hence, this study demonstrates that circulating NA induces NPY release from ventricular sympathetic nerve terminals, the mechanism for which is mediated via β-adrenergic receptors and can be blocked by the non-selective β-blocker, propranolol. KEY POINTS: Cardiovascular disease is characterized by sympathovagal imbalance, with increased plasma noradrenaline (NA) and neuropeptide Y (NPY) concentrations. Increased NPY levels are associated with increased ventricular arrhythmias and mortality in heart failure. Limited data are available on the specific factors that cause NPY release. In this study, fast-scan cyclic voltammetry and capacitive immunoprobes were used to allow for real-time in vivo measurements of interstitial myocardial neurotransmitters and neuropeptides, respectively. Using an in vivo porcine model with cardiac fast-scan cyclic voltammetry and capacitive immunoprobes, it was shown that systemic NA can increase ventricular interstitial NPY levels, suggesting that NA induces NPY release from postganglionic sympathetic nerves. The release of NPY was blocked by administration of the non-selective β-blocker propranolol, suggesting that release of NPY is dependent on activation of β-adrenergic receptors by NA.

Sex- and age-dependent susceptibility to ventricular arrhythmias in the rat heart ex vivo

The incidence of life-threatening ventricular arrhythmias, the most common cause of sudden cardiac death (SCD), depends largely on the arrhythmic substrate that develops in the myocardium during the aging process. There is a large deficit of comparative studies on the development of this substrate in both sexes, with a particular paucity of studies in females. To identify the substrates of arrhythmia, fibrosis, cardiomyocyte hypertrophy, mitochondrial density, oxidative stress, antioxidant defense and intracellular Ca2+ signaling in isolated cardiomyocytes were measured in the hearts of 3- and 24-month-old female and male rats. Arrhythmia susceptibility was assessed in ex vivo perfused hearts after exposure to isoproterenol (ISO) and hydrogen peroxide (H2O2). The number of ventricular premature beats (PVBs), ventricular tachycardia (VT) and ventricular fibrillation (VF) episodes, as well as intrinsic heart rate, QRS and QT duration, were measured in ECG signals recorded from the surfaces of the beating hearts. After ISO administration, VT/VFs were formed only in the hearts of males, mainly older ones. In contrast, H2O2 led to VT/VF formation in the hearts of rats of both sexes but much more frequently in older males. We identified several components of the arrhythmia substrate that develop in the myocardium during the aging process, including high spontaneous ryanodine receptor activity in cardiomyocytes, fibrosis of varying severity in different layers of the myocardium (nonheterogenic fibrosis), and high levels of oxidative stress as measured by nitrated tyrosine levels. All of these elements appeared at a much greater intensity in male individuals during the aging process. On the other hand, in aging females, antioxidant defense at the level of H2O2 detoxification, measured as glutathione peroxidase expression, was weaker than that in males of the same age. We showed that sex has a significant effect on the development of an arrhythmic substrate during aging. This substrate determines the incidence of life-threatening ventricular arrhythmias in the presence of additional stimuli with proarrhythmic potential, such as catecholamine stimulation or oxidative stress, which are constant elements in the pathomechanism of most cardiovascular diseases.

Ischemia-reperfusion myocardial infarction induces remodeling of left cardiac-projecting stellate ganglia neurons

Neurons in the stellate ganglion (SG) provide sympathetic innervation to the heart, brown adipose tissue (BAT), and other organs. Sympathetic innervation to the heart becomes hyperactive following myocardial infarction (MI). The impact of MI on the morphology of cardiac sympathetic neurons is not known, but we hypothesized that MI would stimulate increased cell and dendritic tree size in cardiac neurons. In this study, we examined the effects of ischemia-reperfusion MI on sympathetic neurons using dual retrograde tracing methods to allow detailed characterization of cardiac- and BAT-projecting neurons. Different fluorescently conjugated cholera toxin subunit B (CTb) tracers were injected into the pericardium and the interscapular BAT pads, respectively. Experimental animals received a 45-min occlusion of the left anterior descending coronary artery and controls received sham surgery. One week later, hearts were collected for assessment of MI infarct and SGs were collected for morphological or electrophysiological analysis. Cardiac-projecting SG neurons from MI mice had smaller cell bodies and shorter dendritic trees compared with sham animals, specifically on the left side ipsilateral to the MI. BAT-projecting neurons were not altered by MI, demonstrating the subpopulation specificity of the response. The normal size and distribution differences between BAT- and cardiac-projecting stellate ganglion neurons were not altered by MI. Patch-clamp recordings from cardiac-projecting left SG neurons revealed increased spontaneous excitatory postsynaptic currents despite the decrease in cell and dendritic tree size. Thus, increased dendritic tree size does not contribute to the enhanced sympathetic neural activity seen after MI.NEW & NOTEWORTHY Myocardial infarction (MI) causes structural and functional changes specifically in stellate ganglion neurons that project to the heart, but not in cells that project to brown adipose fat tissue.

mROS‑calcium feedback loop promotes lethal ventricular arrhythmias and sudden cardiac death in early myocardial ischemia

Lethal ventricular arrhythmia‑sudden cardiac death (LVA‑SCD) occurs frequently during the early stage of myocardial ischemia (MI). However, the mechanism underlying higher LVA‑SCD incidence is still poorly understood. The present study aimed to explore the role of mitochondrial reactive oxygen species (mROS) and Ca2+ crosstalk in promoting LVA‑SCD in early MI. RyR2 S2814A mice and their wild‑type littermates were used. MitoTEMPO was applied to scavenge mitochondrial ROS (mROS). Mice were subjected to severe MI and the occurrence of LVA‑SCD was evaluated. Levels of mitochondrial ROS and calcium (mitoCa2+), cytosolic ROS (cytoROS), and calcium (cytoCa2+), RyR2 Ser‑2814 phosphorylation, CaMKII Met‑282 oxidation, mitochondrial membrane potential (MMP), and glutathione/oxidized glutathione (GSH/GSSG) ratio in the myocardia were detected. Dynamic changes in mROS after hypoxia were investigated using H9c2 cells. Moreover, the myocardial phosphoproteome was analyzed to explore the related mechanisms facilitating mROS‑Ca2+ crosstalk and LVA‑SCD. There was a high incidence (~33.9%) of LVA‑SCD in early MI. Mice who underwent SCD displayed notably elevated levels of myocardial ROS and mROS, and the latter was validated in H9c2 cells. These mice also demonstrated overloads of cytoplasmic and mitochondrial Ca2+, decreased MMP and reduced GSH/GSSG ratio, upregulated RyR2‑S2814 phosphorylation and CaMKII‑M282 oxidation and transient hyperphosphorylation of mitochondrial proteomes in the myocardium. mROS‑specific scavenging by a mitochondria‑targeted antioxidant agent (MitoTEMPO) corrected these SCD‑induced alterations. S2814A mice with a genetically inactivated CaMKII phosphorylation site in RyR2 exhibited decreased overloads in cytoplasmic and mitochondrial Ca2+ and demonstrated similar effects as MitoTEMPO to correct SCD‑induced changes and prevent SCD post‑MI. The data confirmed crosstalk between mROS and Ca2+ in promoting LVA‑SCD. Therefore, we provided evidence that there is a higher incidence of LVA‑SCD in early MI, which may be attributed to a positive feedback loop between mROS and Ca2+ imbalance.

Technical development and feasibility of a reusable vest to integrate cardiovascular magnetic resonance with electrocardiographic imaging

BACKGROUND

Electrocardiographic imaging (ECGI) generates electrophysiological (EP) biomarkers while cardiovascular magnetic resonance (CMR) imaging provides data about myocardial structure, function and tissue substrate. Combining this information in one examination is desirable but requires an affordable, reusable, and high-throughput solution. We therefore developed the CMR-ECGI vest and carried out this technical development study to assess its feasibility and repeatability in vivo.

METHODS

CMR was prospectively performed at 3T on participants after collecting surface potentials using the locally designed and fabricated 256-lead ECGI vest. Epicardial maps were reconstructed to generate local EP parameters such as activation time (AT), repolarization time (RT) and activation recovery intervals (ARI). 20 intra- and inter-observer and 8 scan re-scan repeatability tests.

RESULTS

77 participants were recruited: 27 young healthy volunteers (HV, 38.9 ± 8.5 years, 35% male) and 50 older persons (77.0 ± 0.1 years, 52% male). CMR-ECGI was achieved in all participants using the same reusable, washable vest without complications. Intra- and inter-observer variability was low (correlation coefficients [rs] across unipolar electrograms = 0.99 and 0.98 respectively) and scan re-scan repeatability was high (rs between 0.81 and 0.93). Compared to young HV, older persons had significantly longer RT (296.8 vs 289.3 ms, p = 0.002), ARI (249.8 vs 235.1 ms, p = 0.002) and local gradients of AT, RT and ARI (0.40 vs 0.34 ms/mm, p = 0,01; 0.92 vs 0.77 ms/mm, p = 0.03; and 1.12 vs 0.92 ms/mm, p = 0.01 respectively).

CONCLUSION

Our high-throughput CMR-ECGI solution is feasible and shows good reproducibility in younger and older participants. This new technology is now scalable for high throughput research to provide novel insights into arrhythmogenesis and potentially pave the way for more personalised risk stratification.

CLINICAL TRIAL REGISTRATION

Title: Multimorbidity Life-Course Approach to Myocardial Health-A Cardiac Sub-Study of the MRC National Survey of Health and Development (NSHD) (MyoFit46). National Clinical Trials (NCT) number: NCT05455125. URL: https://clinicaltrials.gov/ct2/show/NCT05455125?term=MyoFit&draw=2&rank=1.

Long-term outcomes of patients with ventricular arrhythmias and negative programmed ventricular stimulation followed with implantable loop recorders: Impact of delayed-enhancement cardiac magnetic resonance imaging

BACKGROUND

Programed ventricular stimulation (PVS) is a risk stratification tool in patients at risk for adverse arrhythmia outcomes. Patients with negative PVS may yet be at risk for adverse arrhythmia-related events, particularly in the presence of symptomatic ventricular arrhythmias (VA).

OBJECTIVE

To investigate the long-term outcomes of real-world patients with symptomatic VA without indication for device therapy and negative PVS, and to examine the role of cardiac scaring on arrhythmia recurrence.

METHODS

Patients with symptomatic VA, and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR), and negative PVS testing were included. All patients underwent placement of implantable cardiac monitors (ICM). Survival analysis was performed to investigate the impact of LGE-CMR findings on survival free from adverse arrhythmic events.

RESULTS

Seventy-eight patients were included (age 60 ± 14 years, women n = 36 (46%), ejection fraction 57 ± 9%, cardiomyopathy n = 26 (33%), mitral valve prolapse [MVP] n = 9 (12%), positive LGE-CMR scar n = 49 (62%), history of syncope n = 23 (29%)) including patients with primarily premature ventricular contractions (n = 21) or nonsustained VA (n = 57). Patients were followed for 1.6 ± 1.5 years during which 14 patients (18%) experienced VA requiring treatment (n = 14) or syncope due to bradycardia (n = 2). Four/9 patients (44%) with MVP experienced VA (n = 3) or syncope (n = 1). Baseline characteristics between those with and without adverse events were similar (p > 0.05); however, the presence of cardiac scar on LGE-CMR was independently associated with an increased risk of adverse events (hazard ratio: 5.6 95% confidence interval: [1.2-27], p = 0.03, log-rank p = 0.03).

CONCLUSIONS

In a real-world cohort with long-term follow-up, adverse arrhythmic outcomes occurred in 18% of patients with symptomatic VA despite negative PVS, and this risk was significantly greater in patients with positive DE-CMR scar. Long term-monitoring, including the use of ICM, may be appropriate in these patients.

The understandability and quality of telephone-guided bystander cardiopulmonary resuscitation in the Western Cape province of South Africa: A manikin-based study

Background

The incidence of cardiovascular disease is on the increase in Africa and with it, an increase in the incidence of out-of-hospital cardiac arrest (OHCA). OHCA carries a high mortality, especially in low-resource settings. Interventions to treat OHCA, such as mass cardiopulmonary resuscitation (CPR) training campaigns are costly. One cost-effective and scalable intervention is telephone-guided bystander CPR (tCPR). Little data exists regarding the quality of tCPR. This study aimed to determine quality of tCPR in untrained members of the public. Participants were also asked to provide their views on the understandability of the tCPR instructions.

Methods

This study followed a prospective, simulation-based observational study design. Adult laypeople who have not had previous CPR training were recruited at public CPR training events and asked to perform CPR on a manikin. Quality was assessed in terms of hand placement, compression rate, compression depth, chest recoil, and chest exposure. tCPR instructions were provided by a trained medical provider, via loudspeaker. Participants were also asked to complete a short questionnaire afterwards, detailing the understandability of the tCPR instructions. Data were analysed descriptively and compared to recommended quality guidance.

Results

Fifty participants were enrolled. Hand placement was accurate in 74 % (n = 37) of participants, while compression depth and chest recoil only had compliance in 20 % (n = 10) and 24 % (n = 12) of participants, respectively. The mean compression rate was within guidelines in just under half (48 %, n = 24) of all participants. Only 20 (40 %) participants exposed the manikin's chest. Only 46 % (n = 23) of participants felt that the overall descriptions offered during the tCPR guidance were understandable, while 80 % (n = 40) and 36 % (n = 18) felt that the instructions on hand placement and compression rate were understandable, respectively. Lastly, 94 % (n = 47) of participants agreed that they would be more likely to perform bystander CPR if they were provided with tCPR.

Conclusion

The quality of CPR performed by laypersons is generally suboptimal and this may affect patient outcomes. There is an urgent need to develop more understandable tCPR algorithms that may encourage bystanders to start CPR and optimise its quality.

Lamotrigine use and potential for adverse cardiac effects: A retrospective evaluation in a Veteran population

OBJECTIVE

To identify the impact of lamotrigine (LTG) on cardiac rhythm and conduction abnormalities for Veterans, an especially vulnerable population.

BACKGROUND

In October 2020 the US Food and Drug Administration (FDA) added a new warning to the label of lamotrigine (Lamictal™) regarding its potential to cause cardiac rhythm and conduction abnormalities [1]. This warning came following in vitro data which suggested Class IB antiarrhythmic effects occurring at clinically achievable concentrations of lamotrigine [2]. However, it is unclear whether the in vitro findings will result in adverse clinical outcomes. Our objective was to assess for evidence for adverse clinical outcomes in a vulnerable population and examine for subtler signs of an association between lamotrigine and cardiac rhythm disturbances.

METHODS

A retrospective chart review was conducted using records between 10-01-2017 and 07-06-2021, identifying patients at the William S. Middleton Memorial Veterans Hospital who were prescribed lamotrigine. Data collected included: dates of lamotrigine initiation or discontinuation, lamotrigine dosing over the time of the prescription and maximum lamotrigine dose, any cardiac-related ICD-10-CM codes or a history of a cardiology appointment, EKGs with any abnormalities or changes, any concomitantly prescribed medications with known potential to cause cardiac abnormalities, any cardiac deaths. This retrospective chart review was approved by the University of Wisconsin-Madison Institutional Review Board.

RESULTS

Two hundred and thirty-three (189 male) patients with a lamotrigine prescription and 41.2 % (n = 96) of these patients had an EKG performed while prescribed lamotrigine. The average age of patients was 64.3 ± 13.0 (range 29 to 90) years and mean maximum lamotrigine daily dose was 250.8 ± 148.2 mg (range 25 to 800 mg). Nearly half (47.9 %, 46/96) of the patients were prescribed a concomitant sodium channel blocking medication in addition to lamotrigine. Eighty-four of the patients (87.5 %, 84/96) had a cardiac diagnosis, while 12 (12.5 %, 12/96) did not. A total of 12 deaths occurred within the review period, with two cardiac deaths from congestive heart failure. Four cases did not have information on cause of death. No LTG-associated cardiac adverse effects were noted as part of clinical care, though rash was noted in 5 cases. A total of 7 (7.3 %, 7/96) patients were found to have EKG abnormalities potentially related to lamotrigine, including 7.1 % (6/84) of those with a cardiac diagnosis and 8.3 % (1/12) of those without a cardiac diagnosis.

CONCLUSIONS

While recent FDA warnings have suggested caution regarding cardiac complications associated with lamotrigine based on in vitro studies, the clinical implications are uncertain. Despite selecting a particularly vulnerable population, this retrospective chart review did not identify any deaths due to cardiac rhythm or conduction causes, nor demonstrate unambiguous cardiac complications related to lamotrigine. Even using permissive criteria (including any prolonged PR or QTc) to examine for subtle effects, only a low incidence (<10 %) of potential complications was found. Broader implications of this study are limited by the number of patients included and the retrospective nature of the study. Therefore, further studies are warranted to evaluate a link between cardiac complications and the use of lamotrigine, including the role of concomitant medications such as other sodium channel blocking agents and psychotropic medications.

Plasma Ceramides and Sphingomyelins and Sudden Cardiac Death in the Cardiovascular Health Study

Importance

Sphingolipids, including ceramides and sphingomyelins, may influence the pathophysiology and risk of sudden cardiac death (SCD) through multiple biological activities. Whether the length of the fatty acid acylated to plasma sphingolipid species is associated with SCD risk is not known.

Objective

To determine whether the saturated fatty acid length of plasma ceramides and sphingomyelins influences the association with SCD risk.

Design, Setting, and Participants

In this cohort study, multivariable Cox proportional hazards regression models were used to examine the association of sphingolipid species with SCD risk. The study population included 4612 participants in the Cardiovascular Health Study followed up prospectively for a median of 10.2 (IQR, 5.5-11.6) years. Baseline data were collected from January 1992 to December 1995 during annual examinations. Data were analyzed from February 11, 2020, to September 9, 2023.

Exposures

Eight plasma sphingolipid species (4 ceramides and 4 sphingomyelins) with saturated fatty acids of 16, 20, 22, and 24 carbons.

Main Outcome and Measure

Association of plasma ceramides and sphingomyelins with saturated fatty acids of different lengths with SCD risk.

Results

Among the 4612 CHS participants included in the analysis (mean [SD] age, 77 [5] years; 2724 [59.1%] women; 6 [0.1%] American Indian; 4 [0.1%] Asian; 718 [15.6%] Black; 3869 [83.9%] White, and 15 [0.3%] Other), 215 SCD cases were identified. In adjusted Cox proportional hazards regression analyses, plasma ceramides and sphingomyelins with palmitic acid (Cer-16 and SM-16) were associated with higher SCD risk per higher SD of log sphingolipid levels (hazard ratio [HR] for Cer-16, 1.34 [95% CI, 1.12-1.59]; HR for SM-16, 1.37 [95% CI, 1.12-1.67]). Associations did not differ by baseline age, sex, race, or body mass index. No significant association of SCD with sphingolipids with very-long-chain saturated fatty acids was observed after correction for multiple testing (HR for ceramide with arachidic acid, 1.06 [95% CI, 0.90-1.24]; HR for ceramide with behenic acid, 0.92 [95% CI, 0.77-1.10]; HR for ceramide with lignoceric acid, 0.92 [95% CI, 0.77-1.09]; HR for sphingomyelin with arachidic acid, 0.83 [95% CI, 0.71-0.98]; HR for sphingomyelin with behenic acid, 0.84 [95% CI, 0.70-1.00]; HR for sphingomyelin with lignoceric acid, 0.86 [95% CI, 0.72-1.03]).

Conclusions and Relevance

The findings of this large, population-based cohort study of SCD identified that higher plasma levels of Cer-16 and SM-16 were associated with higher risk of SCD. Future studies are needed to examine the underlying mechanism of these associations.

The impact of modifiable risk factors in the association between socioeconomic status and sudden cardiac death in a prospective cohort study: equal access to healthcare, unequal outcome

AIMS

Low socioeconomic status is associated with all-cause mortality and cardiac risk factors. Furthermore, sudden cardiac death (SCD) is among the leading causes of death in the general population, and an identification of high-risk subgroups is needed. The aim of this study was to investigate the association between income and education level and incidence of SCD and to calculate the impact of modifiable mediating risk factors.

METHODS AND RESULTS

Participants in the Copenhagen City Heart Study were followed up from 1993 to 2016. Sudden cardiac death was identified using high-quality death certificates, autopsy reports, discharge summaries, and national registry data. Hazard ratios were calculated using Cox proportional hazards regression, and adjusted cumulative incidences were predicted using cause-specific Cox models. Mediation analyses were performed using a marginal structural model approach. During 24 years of follow-up, 10 006 people participated, whereof 5514 died during the study period with 822 SCDs. Compared with long education, persons with elementary school level education had an SCD incidence rate ratio (IRR) of 2.48 [95% confidence interval (CI) 1.86-3.31], and low income was likewise associated with an SCD IRR of 2.34 (95% CI 1.85-2.96) compared with high income. In the association between education and SCD, the combined mediating effect of smoking, physical activity, and body mass index accounted for ∼20% of the risk differences.

CONCLUSION

We observed an inverse association between both income and education and the risk of SCD, which was only in part explained by common cardiac risk factors, implying that further research into the competing causes of SCD is needed and stressing the importance of targeted preventive measures.

Causal influence of sleeping phenotypes on the risk of coronary artery disease and sudden cardiac arrest: A Mendelian randomization analysis

OBJECTIVES

To assess the causal influence of sleep and circadian traits on coronary artery disease and sudden cardiac arrest with adjustment for obesity through a two-sample Mendelian randomization study.

METHODS

We used summary statistics of 5 sleep and circadian traits for genome-wide association studies, including chronotype, sleep duration, long sleep (≥9 h a day), short sleep (<7 h a day), and insomnia (sample size range: 237,622-651,295). Coronary artery disease genome-wide association studies with 60,801 cases and 123,504 controls, sudden cardiac arrest genome-wide association studies with 3939 cases and 25,989 controls, and obesity genome-wide association studies with 806,834 individuals were also used. Multivariable Mendelian randomization was performed to estimate the causality.

RESULTS

After adjusting for obesity, genetically predicted short sleep (odds ratio = 1.87 and p = .02), and genetically predicted insomnia (odds ratio = 1.17 and p = .001) were causally associated with increased odds of coronary artery disease. Genetically predicted long sleep (odds ratio = 0.06 and p = .02) and genetically predicted longer sleep duration (odds ratio = 0.36 for per-hour increase in sleep duration and p = .0006) were causally associated with decreased odds of sudden cardiac arrest.

CONCLUSIONS

The findings of this Mendelian randomization study indicate that insomnia and short sleep contribute to the development of coronary artery disease, whereas a longer sleep duration protects from sudden cardiac arrest, independent of the influence of obesity. The mechanisms underlying these associations warrant further investigation.

Prevalence and factors associated with initial and subsequent shockable cardiac arrest rhythms and their association with patient outcomes in dogs and cats undergoing cardiopulmonary resuscitation: A RECOVER registry study

OBJECTIVE

To report the prevalence of initial shockable cardiac arrest rhythms (I-SHKR), incidence of subsequent shockable cardiac arrest rhythms (S-SHKR), and factors associated with I-SHKRs and S-SHKRs and explore their association with return of spontaneous circulation (ROSC) rates in dogs and cats undergoing CPR.

DESIGN

Multi-institutional prospective case series from 2016 to 2021, retrospectively analyzed.

SETTING

Eight university and eight private practice veterinary hospitals.

ANIMALS

A total of 457 dogs and 170 cats with recorded cardiac arrest rhythm and event outcome reported in the Reassessment Campaign on Veterinary Resuscitation CPR registry.

MEASUREMENTS AND MAIN RESULTS

Logistic regression was used to evaluate association of animal, hospital, and arrest variables with I-SHKRs and S-SHKRs and with patient outcomes. Odds ratios (ORs) were generated, and significance was set at P < 0.05. Of 627 animals included, 28 (4%) had I-SHKRs. Odds for I-SHKRs were significantly higher in animals with a metabolic cause of arrest (OR 7.61) and that received lidocaine (OR 17.50) or amiodarone (OR 21.22) and significantly lower in animals experiencing arrest during daytime hours (OR 0.22), in the ICU (OR 0.27), in the emergency room (OR 0.13), and out of hospital (OR 0.18) and that received epinephrine (OR 0.19). Of 599 initial nonshockable rhythms, 74 (12%) developed S-SHKRs. Odds for S-SHKRs were significantly higher in animals with higher body weight (OR 1.03), hemorrhage (OR 2.85), or intracranial cause of arrest (OR 3.73) and that received epinephrine (OR 11.36) or lidocaine (OR 18.72) and significantly decreased in those arresting in ICU (OR 0.27), emergency room (OR 0.29), and out of hospital (OR 0.38). Overall, 171 (27%) animals achieved ROSC, 81 (13%) achieved sustained ROSC, and 15 (2%) survived. Neither I-SHKRs nor S-SHKRs were significantly associated with ROSC.

CONCLUSIONS

I-SHKRs and S-SHKRs occur infrequently in dogs and cats undergoing CPR and are not associated with increased ROSC rates.

Triglyceride-glucose index is associated with the occurrence and prognosis of cardiac arrest: a multicenter retrospective observational study

BACKGROUND

Triglyceride-glucose (TyG) index is an efficient indicator of insulin resistance and is proven to be a valuable marker in several cardiovascular diseases. However, the relationship between TyG index and cardiac arrest (CA) remains unclear. The present study aimed to investigate the association of the TyG index with the occurrence and clinical outcomes of CA.

METHODS

In this retrospective, multicenter, observational study, critically ill patients, including patients post-CA, were identified from the eICU Collaborative Research Database and evaluated. The TyG index for each patient was calculated using values of triglycerides and glucose recorded within 24 h of intensive care unit (ICU) admission. In-hospital mortality and ICU mortality were the primary clinical outcomes. Logistic regression, restricted cubic spline (RCS), and correlation analyses were performed to explore the relationship between the TyG index and clinical outcomes. Propensity score matching (PSM), overlap weighting (OW), and inverse probability of treatment weighting (IPTW) were adopted to balance the baseline characteristics of patients and minimize selection bias to confirm the robustness of the results. Subgroup analysis based on different modifiers was also performed.

RESULTS

Overall, 24,689 critically ill patients, including 1021 patients post-CA, were enrolled. The TyG index was significantly higher in patients post-CA than in those without CA (9.20 (8.72-9.69) vs. 8.89 (8.45-9.41)), and the TyG index had a moderate discrimination ability to identify patients with CA from the overall population (area under the curve = 0.625). Multivariate logistic regression indicated that the TyG index was an independent risk factor for in-hospital mortality (OR = 1.28, 95% CI: 1.03-1.58) and ICU mortality (OR = 1.27, 95% CI: 1.02-1.58) in patients post-CA. RCS curves revealed that an increased TyG index was linearly related to higher risks of in-hospital and ICU mortality (P for nonlinear: 0.225 and 0.271, respectively). Even after adjusting by PSM, IPTW, and OW, the TyG index remained a risk factor for in-hospital mortality and ICU mortality in patients experiencing CA, which was independent of age, BMI, sex, etc. Correlation analyses revealed that TyG index was negatively correlated with the neurological status of patients post-CA.

CONCLUSION

Elevated TyG index is significantly associated with the occurrence of CA and higher mortality risk in patients post-CA. Our findings extend the landscape of TyG index in cardiovascular diseases, which requires further prospective cohort study.

Validation of the ARIC prediction model for sudden cardiac death in the European population: The ESCAPE-NET project: Predicting sudden cardiac death in European adults

BACKGROUND

Sudden cardiac death is responsible for 10-20% of all deaths in Europe. The current study investigates how well the risk of sudden cardiac death can be predicted. To this end, we validated a previously developed prediction model for sudden cardiac death from the Atherosclerosis Risk in Communities study (USA).

METHODS

Data from participants of the Copenhagen City Heart Study (CCHS) (n=9988) was used to externally validate the previously developed prediction model for sudden cardiac death. The model's performance was assessed through discrimination (C-statistic) and calibration by the Hosmer-Lemeshow goodness-of-fit (HL) statistics suited for censored data and visual inspection of calibration plots. Additional validation was performed using data from the Hoorn Study (N=2045), employing the same methods.

RESULTS

During ten years of follow-up of CCHS participants (mean age: 58.7 years, 56.2% women), 425 experienced SCD (4.2%). The prediction model showed good discrimination for sudden cardiac death risk (C-statistic: 0.81, 95% CI:0.79-0.83). Calibration was robust (HL statistic: p=0.8). Visual inspection of the calibration plot showed that the calibration could be improved. Sensitivity was 89.8%, and specificity was 60.6%. The positive and negative predictive values were 10.1% and 99.2%. Model performance was similar in the Hoorn Study (C-statistic: 0.81, 95% CI: 0.77-0.85 and the HL statistic: 1.00).

CONCLUSION

Our study showed that the previously developed prediction model in North American adults performs equally well in identifying those at risk for sudden cardiac death in a general North-West European population. However, the positive predictive value is low.

"It's Overwhelming With the Grief" A Qualitative Study of Families' Experiences When a Young Relative Dies of Sudden Cardiac Death

BACKGROUND

Sudden cardiac death (SCD) in younger individuals is frequently caused by heritable cardiac conditions. The unexpected nature of SCD leaves families with many unanswered questions and an insufficient understanding of the cause of death and their own risk for heritable disease. We explored the experiences of families of young SCD victims upon learning about their relative's cause of death and how they perceive their own risk for heritable cardiac conditions.

METHODS

We conducted a qualitative descriptive study, by interviewing families of young (ages 12-45) SCD victims, who died between 2014 and 2018 from a heritable cardiac condition and were investigated by the Office of the Chief Coroner of Ontario, Canada. We used thematic analysis to analyze the transcripts.

RESULTS

Between 2018 and 2020, we interviewed 19 family members, of which 10 were males and 9 were females, ages ranging from 21 to 65 (average 46.2±13.1). Four main themes were revealed, each representing a distinct time period that families experience along a trajectory: (1) interactions between bereaved family and others, in particular coroners, shaped their search for answers about their relative's cause of death, with the types, formats, and timing of communication varying by case; (2) searching for answers and processing the cause of death; (3) incidental implications of the SCD event, such as financial strain and lifestyle changes contributed to cumulative stress; (4) receiving answers (or not) and moving forward.

CONCLUSIONS

Families rely on communication with others, yet the type, formats, and timing of information received varies, which can influence families' experiences of processing the death (and its cause), their perceived risk and their decision to pursue cascade screening. These results may provide key insights for the interprofessional health care team responsible for the delivery and communication of the cause of death to families of SCD victims.

GABAergic Signaling during Spinal Cord Stimulation Reduces Cardiac Arrhythmias in a Porcine Model

BACKGROUND

Neuraxial modulation, including spinal cord stimulation, reduces cardiac sympathoexcitation and ventricular arrhythmogenesis. There is an incomplete understanding of the molecular mechanisms through which spinal cord stimulation modulates cardiospinal neural pathways. The authors hypothesize that spinal cord stimulation reduces myocardial ischemia-reperfusion-induced sympathetic excitation and ventricular arrhythmias through γ-aminobutyric acid (GABA)-mediated pathways in the thoracic spinal cord.

METHODS

Yorkshire pigs were randomized to control (n = 11), ischemia-reperfusion (n = 16), ischemia-reperfusion plus spinal cord stimulation (n = 17), ischemia-reperfusion plus spinal cord stimulation plus γ-aminobutyric acid type A (GABAA) or γ-aminobutyric acid type B (GABAB) receptor antagonist (GABAA, n = 8; GABAB, n = 8), and ischemia-reperfusion plus GABA transaminase inhibitor (GABAculine, n = 8). A four-pole spinal cord stimulation lead was placed epidurally (T1 to T4). GABA modulating pharmacologic agents were administered intrathecally. Spinal cord stimulation at 50 Hz was applied 30 min before ischemia. A 56-electrode epicardial mesh was used for high-resolution electrophysiologic recordings, including activation recovery intervals and ventricular arrhythmia scores. Immunohistochemistry and Western blots were performed to measure GABA receptor expression in the thoracic spinal cord.

RESULTS

Cardiac ischemia led to myocardial sympathoexcitation with reduction in activation recovery interval (mean ± SD, -42 ± 11%), which was attenuated by spinal cord stimulation (-21 ± 17%, P = 0.001). GABAA and GABAB receptor antagonists abolished spinal cord stimulation attenuation of sympathoexcitation (GABAA, -9.7 ± 9.7%, P = 0.043 vs. ischemia-reperfusion plus spinal cord stimulation; GABAB, -13 ± 14%, P = 0.012 vs. ischemia-reperfusion plus spinal cord stimulation), while GABAculine alone caused a therapeutic effect similar to spinal cord stimulation (-4.1 ± 3.7%, P = 0.038 vs. ischemia-reperfusion). The ventricular arrhythmia score supported these findings. Spinal cord stimulation during ischemia-reperfusion increased GABAA receptor expression with no change in GABAB receptor expression.

CONCLUSIONS

Thoracic spinal cord stimulation reduces ischemia-reperfusion-induced sympathoexcitation and ventricular arrhythmias through activation of GABA signaling pathways. These data support the hypothesis that spinal cord stimulation-induced release of GABA activates inhibitory interneurons to decrease primary afferent signaling from superficial dorsal horn to sympathetic output neurons in the intermediolateral nucleus.

EDITOR’S PERSPECTIVE

Incidence of sudden cardiac arrest and sudden cardiac death after unstable angina pectoris and myocardial infarction

BACKGROUND

Sudden cardiac arrests (SCA) and sudden cardiac deaths (SCD) are believed to account for a large proportion of deaths due to cardiovascular causes. The purpose of this study is to provide comprehensive information on the epidemiology of SCAs and SCDs after acute coronary syndrome.

METHODS

The incidence of SCA (including SCDs) was studied retrospectively among 10,316 consecutive patients undergoing invasive evaluation for acute coronary syndrome (ACS) between 2007 and 2018 at Tays Heart Hospital (sole provider of specialized cardiac care for a catchment area of over 0.5 million residents). Baseline and follow-up information was collected by combining information from the hospital's electronic health records, death certificate data, and a full-disclosure review of written patient records and accounts of the circumstances leading to death.

RESULTS

During 12 years of follow-up, the cumulative incidence of SCAs (including SCDs) was 9.8% (0.8% annually) and that of SCDs 5.4% (0.5% annually). Cumulative incidence of SCAs in patients with ST-elevation myocardial infarction, non-ST-elevation myocardial infarction and unstable angina pectoris were: 11.9%,10.2% and 5.7% at 12 years. SCAs accounted for 30.5% (n = 528/1,732) of all deaths due to cardiovascular causes. The vast majority of SCAs (95.6%) occurred in patients without implantable cardioverter defibrillator (ICD) devices or among patients with no recurrent hospitalizations for coronary artery disease (89.1%).

CONCLUSIONS

SCAs accounted for less than a third of all deaths due to cardiovascular causes among patients with previous ACS. Incidence of SCA is highest among STEMI and NSTEMI patients. After the hospital discharge, most of SCAs happen to NSTEMI patients.

Experimental heart failure models in small animals

Heart failure (HF) is one of the most critical health and economic burdens worldwide, and its prevalence is continuously increasing. HF is a disease that occurs due to a pathological change arising from the function or structure of the heart tissue and usually progresses. Numerous experimental HF models have been created to elucidate the pathophysiological mechanisms that cause HF. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. During the past few decades, animal models have provided new insights into the complex pathogenesis of HF. Success in the pathophysiology and treatment of HF has been achieved by using animal models of HF. The development of new in vivo models is critical for evaluating treatments such as gene therapy, mechanical devices, and new surgical approaches. However, each animal model has advantages and limitations, and none of these models is suitable for studying all aspects of HF. Therefore, the researchers have to choose an appropriate experimental model that will fully reflect HF. Despite some limitations, these animal models provided a significant advance in the etiology and pathogenesis of HF. Also, experimental HF models have led to the development of new treatments. In this review, we discussed widely used experimental HF models that continue to provide critical information for HF patients and facilitate the development of new treatment strategies.

Risk factors of sudden cardiac death in women: A 10 years study in Tunisia

BACKGROUND

Sudden cardiac death (SCD) represents a frequent etiology of sudden death. It represents a major public health issue. Few data about SCD in women are available from the Arab world. Our work aimed to analyze the risk factors of sudden cardiac death in Tunisian women in comparison with men.

METHODS

A cross-sectional retrospective study including all sudden cardiac death cases, conducted in the Forensic Medicine Department of the main teaching hospital of Tunis, between January 2010 and December 2019.

RESULTS

We counted 417 cases of sudden cardiac death in women representing 17.5% of the total number of sudden cardiac deaths recorded during the study period. The average age was 60.03 ± 15.01 years with a predominance of urban married women. The most frequent cardiac risk factors were high blood pressure (50%), diabetes (36.2%), and cardiac disease history (34.2%). Predominately married women with a history of High blood pressure and diabetes, had a high predictive of sudden cardiac death.

CONCLUSION

Cardiac sudden death is no longer a male focused issue. As a matter of facts Rates of SCD in women are rising with a different pattern. We will highlight the importance of adopting specific preventive measures of SCD in female.

Vagus Nerve Stimulation and Its Cardioprotective Abilities: A Systematic Review

Despite the vagus nerve stimulator (VNS) being used in neuroscience, it has recently been highlighted that it has cardioprotective functions. However, many studies related to VNS are not mechanistic in nature. This systematic review aims to focus on the role of VNS in cardioprotective therapy, selective vagus nerve stimulators (sVNS), and their functional capabilities. A systemic review of the current literature was conducted on VNS, sVNS, and their ability to induce positive effects on arrhythmias, cardiac arrest, myocardial ischemia/reperfusion injury, and heart failure. Both experimental and clinical studies were reviewed and assessed separately. Of 522 research articles retrieved from literature archives, 35 met the inclusion criteria and were included in the review. Literature analysis proves that combining fiber-type selectivity with spatially-targeted vagus nerve stimulation is feasible. The role of VNS as a tool for modulating heart dynamics, inflammatory response, and structural cellular components was prominently seen across the literature. The application of transcutaneous VNS, as opposed to implanted electrodes, provides the best clinical outcome with minimal side effects. VNS presents a method for future cardiovascular treatment that can modulate human cardiac physiology. However, continued research is needed for further insight.

Mitochondrial Dysfunction in Cardiac Arrhythmias

Electrophysiological and structural disruptions in cardiac arrhythmias are closely related to mitochondrial dysfunction. Mitochondria are an organelle generating ATP, thereby satisfying the energy demand of the incessant electrical activity in the heart. In arrhythmias, the homeostatic supply-demand relationship is impaired, which is often accompanied by progressive mitochondrial dysfunction leading to reduced ATP production and elevated reactive oxidative species generation. Furthermore, ion homeostasis, membrane excitability, and cardiac structure can be disrupted through pathological changes in gap junctions and inflammatory signaling, which results in impaired cardiac electrical homeostasis. Herein, we review the electrical and molecular mechanisms of cardiac arrhythmias, with a particular focus on mitochondrial dysfunction in ionic regulation and gap junction action. We provide an update on inherited and acquired mitochondrial dysfunction to explore the pathophysiology of different types of arrhythmias. In addition, we highlight the role of mitochondria in bradyarrhythmia, including sinus node dysfunction and atrioventricular node dysfunction. Finally, we discuss how confounding factors, such as aging, gut microbiome, cardiac reperfusion injury, and electrical stimulation, modulate mitochondrial function and cause tachyarrhythmia.

Waterpipe Use and Its Cardiovascular Effects: A Systematic Review and Meta-Analysis of Case-Control, Cross-Sectional, and Non-Randomized Studies

Approximately 100 million people globally smoke cigarettes, making it a significant and quickly spreading global tobacco epidemic. Substance use disorders are frequently evaluated by non-randomized studies. Tobacco use and its impacts on the cardiovascular system were the subjects of a comprehensive search across five electronic databases: Cochrane, MEDLINE, Scopus, Embase, and PubMed. The findings demonstrated that waterpipe smokers in comparison to non-smokers have immediate elevations in heart rate and blood pressure, lower levels of high-density lipoprotein, higher levels of low-density lipoprotein, higher levels of triglycerides, higher levels of fasting blood glucose, and a higher heart rate. Users of waterpipes and cigarettes had similar average heart rates, blood pressure, and lipid levels, with the exception that waterpipe smokers had greater total cholesterol. Smoking a waterpipe has significant negative effects on the cardiovascular system comparable to cigarette smoking, and non-randomized studies proved to yield substantial evidence related to its cardiovascular effects. Such study designs can be used to evaluate substance use and its cardiovascular impact.

Application of postmortem imaging modalities in cases of sudden death due to cardiovascular diseases-current achievements and limitations from a pathology perspective : Endorsed by the Association for European Cardiovascular Pathology and by the International Society of Forensic Radiology and Imaging

Postmortem imaging (PMI) is increasingly used in postmortem practice and is considered a potential alternative to a conventional autopsy, particularly in case of sudden cardiac deaths (SCD). In 2017, the Association for European Cardiovascular Pathology (AECVP) published guidelines on how to perform an autopsy in such cases, which is still considered the gold standard, but the diagnostic value of PMI herein was not analyzed in detail. At present, significant progress has been made in the PMI diagnosis of acute ischemic heart disease, the most important cause of SCD, while the introduction of postmortem CT angiography (PMCTA) has improved the visualization of several parameters of coronary artery pathology that can support a diagnosis of SCD. Postmortem magnetic resonance (PMMR) allows the detection of acute myocardial injury-related edema. However, PMI has limitations when compared to clinical imaging, which severely impacts the postmortem diagnosis of myocardial injuries (ischemic versus non-ischemic), the age-dating of coronary occlusion (acute versus old), other potentially SCD-related cardiac lesions (e.g., the distinctive morphologies of cardiomyopathies), aortic diseases underlying dissection or rupture, or pulmonary embolism. In these instances, PMI cannot replace a histopathological examination for a final diagnosis. Emerging minimally invasive techniques at PMI such as image-guided biopsies of the myocardium or the aorta, provide promising results that warrant further investigations. The rapid developments in the field of postmortem imaging imply that the diagnosis of sudden death due to cardiovascular diseases will soon require detailed knowledge of both postmortem radiology and of pathology.

Trends and Outcomes in Cardiac Arrest Among Heart Failure Admissions

There is limited large, national data investigating the prevalence, characteristics, and outcomes of cardiac arrest (CA) in patients hospitalized for heart failure (HF). The goal of this study was to examine the characteristics, trends, and outcomes of HF hospitalizations complicated by in-hospital CA. We used the National Inpatient Sample to identify all primary HF admissions from 2016 to 2019. Cohorts were built based on the presence of a codiagnosis of CA. Diagnoses were identified using International Classification of Diseases, Tenth Revision, Clinical Modification codes. Associations with CA were then analyzed using multivariate logistic regression. We identified a total of 4,905,564 HF admissions, 56,170 (1.1%) of which had CA. Hospitalizations complicated by CA were significantly more likely to be male, to have coronary artery disease, renal disease, and less likely to be White (p <0.001, all). Age <65 (odds ratio [OR] 1.18, p <0.001), renal disease (OR 2.41, p <0.001), and coronary artery disease (OR 1.26, p <0.001) had higher odds of CA while female gender (OR 0.84, confidence interval [CI] 0.83 to 0.86, p <0.001) or HFpEF (OR 0.49, CI 0.48 to 0.50, p <0.001) had lower odds of CA. Patients with CA had higher inpatient mortality (CA 54.2% vs no CA 2.1%, p <0.001), which persisted after multivariate adjustment (OR 64.8, CI 63.5 to 66.0, p <0.001). CA occurs in >1 in 1,000 HF hospitalizations and remains a prominent and serious event associated with a high mortality. Further research is needed to examine long-term outcomes and mechanical circulatory support utilization with more granularity in HF patients with in-hospital CA.

Electrophysiology practice in low- and middle-income countries: An updated review on access to care and health delivery

Concurrent with the epidemiological transition to cardiovascular diseases in low- and middle-income countries (LMICs), the burden of arrhythmias is increasing significantly. However, registries of electrophysiological disorders and their management in LMICs are limited. The advancement of telemedicine technology can play a distinctive role in providing accurate diagnoses in resource-limited settings. The estimated pacemaker implantation requirements (1 million per year) demand an alternate source of pacemakers, including reused permanent pacemakers and implantable cardioverter-defibrillators. In addition, the majority of supraventricular tachycardias and atrial fibrillation can be managed with radiofrequency ablation, which not only is cost-effective but is curative for most patients.

Genome Editing and Myocardial Development

Congenital heart disease (CHD) has a strong genetic etiology, making it a likely candidate for therapeutic intervention using genetic editing. Complex genetics involving an orchestrated series of genetic events and over 400 genes are responsible for myocardial development. Cooperation is required from a vast series of genetic networks, and mutations in such can lead to CHD and cardiovascular abnormalities, affecting up to 1% of all live births. Genome editing technologies are becoming better studied and with time and improved logistics, CHD could be a prime therapeutic target. Syndromic, nonsyndromic, and cases of familial inheritance all involve identifiable causative mutations and thus have the potential for genome editing therapy. Mouse models are well-suited to study and predict clinical outcome. This review summarizes the anatomical and genetic timeline of myocardial development in both mice and humans, the potential of gene editing in typical CHD categories, as well as the use of mice thus far in reproducing models of human CHD and correcting the mutations that create them.

Community Cardiac Arrest as a Challenge for Emergency Medical Services in Poland

The problem of cardiac arrest, particularly out-of-hospital cardiac arrest (OHCA), is the subject of continuous research. The aim of this study was to analyze the use of an automated external defibrillator (AED) during the resuscitation of an adult in public places in Poland between 2015 and 2020. A retrospective analysis of the selected documentation obtained from AED distributors, the medical records obtained from the emergency call center, and the emergency medical teams was conducted. During the analysis period, there were 100 cases of recorded and documented use of AEDs in OHCAs in public places. In 70% of the cases, defibrillation was performed with an AED. This result could be higher, but the study's methodology and limited access to data only allowed for this result. In Poland, there are no legal acts on the registration of automatic external defibrillators and their implementation. Appropriate registries should be introduced nationwide as soon as possible. Due to the inadequacy of the medical records of the emergency medical teams to record the use of automated external defibrillators by a bystander to an incident, changes to these documents should be pursued. Based on such a small cohort, it is not possible to conclude that the return of spontaneous blood circulation is correlated with the use of AEDs and public access to defibrillation PADs.

Guidelines for assessment of cardiac electrophysiology and arrhythmias in small animals

Cardiac arrhythmias are a major cause of morbidity and mortality worldwide. Although recent advances in cell-based models, including human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), are contributing to our understanding of electrophysiology and arrhythmia mechanisms, preclinical animal studies of cardiovascular disease remain a mainstay. Over the past several decades, animal models of cardiovascular disease have advanced our understanding of pathological remodeling, arrhythmia mechanisms, and drug effects and have led to major improvements in pacing and defibrillation therapies. There exist a variety of methodological approaches for the assessment of cardiac electrophysiology and a plethora of parameters may be assessed with each approach. This guidelines article will provide an overview of the strengths and limitations of several common techniques used to assess electrophysiology and arrhythmia mechanisms at the whole animal, whole heart, and tissue level with a focus on small animal models. We also define key electrophysiological parameters that should be assessed, along with their physiological underpinnings, and the best methods with which to assess these parameters.

Sudden Cardiac Death Prevention in Patients with Ischemic Heart Disease-Beyond the Ejection Fraction

Sudden cardiac death (SCD) in patients with ischemic heart disease remains a leading cause of death. Prediction of who is at risk is based on the left ventricular ejection fraction (EF). However, the majority of victims of SCD have a normal EF, and the majority of patients implanted with an implantable cardioverter- defibrillator based on their EF are never treated by their device. Several parameters could allow better prediction of SCD. Several signs on the ECG and Periodic Repolarization Dynamics have been associated with increased risk. Elevated serum biomarkers such as pro-B type natriuretic peptides and serum soluble suppression of tumorigenicity 2 protein (sST2) are predictive of SCD. On the echocardiogram, global longitudinal strain, speckle tracking and relative wall thickness have been implicated. Programmed ventricular stimulation studies and cardiac magnetic resonance are promising modalities that could be further investigated. In conclusion, the EF is an imperfect tool for predicting SCD. Using the modalities reviewed, a model could be created for better prediction of patients at risk.

Arrhythmic Sudden Cardiac Death in Heart Failure With Preserved Ejection Fraction: Mechanisms, Genetics, and Future Directions

Heart failure with preserved ejection fraction (HFpEF) is an increasingly recognized disorder. Many clinical trials have failed to demonstrate benefit in patients with HFpEF but have recognized alarming rates of sudden cardiac death (SCD). Genetic testing has become standard in the workup of patients with otherwise unexplained cardiac arrest, but the genetic architecture of HFpEF, and the overlap of a genetic predisposition to HFpEF and arrhythmias, is poorly understood. An understanding of the genetics of HFpEF and related SCD has the potential to redefine and generate novel diagnostic, prognostic, and therapeutic tools. In this review, we examine recent pathophysiological and clinical advancements in our understanding of HFpEF, which reinforce the heterogeneity of the condition. We also discuss data describing SCD events in patients with HFpEF and review the current literature on genetic underpinnings of HFpEF. Mechanisms of arrhythmogenesis which may lead to SCD in this population are also explored. Lastly, we outline several areas of promise for experimentation and clinical trials that have the potential to further advance our understanding of and contribute to improved clinical care of this patient population.

A CACNA1C variant associated with cardiac arrhythmias provides mechanistic insights in the calmodulation of L-type Ca2+ channels

We recently reported the identification of a de novo single nucleotide variant in exon 9 of CACNA1C associated with prolonged repolarization interval. Recombinant expression of the glycine to arginine variant at position 419 produced a gain in the function of the L-type Ca_V1.2 channel with increased peak current density and activation gating but without significant decrease in the inactivation kinetics. We herein reveal that these properties are replicated by overexpressing calmodulin (CaM) with Ca_V1.2 WT and are reversed by exposure to the CaM antagonist W-13. Phosphomimetic (T79D or S81D), but not phosphoresistant (T79A or S81A), CaM surrogates reproduced the impact of CaM WT on the function of Ca_V1.2 WT. The increased channel activity of Ca_V1.2 WT following overexpression of CaM was found to arise in part from enhanced cell surface expression. In contrast, the properties of the variant remained unaffected by any of these treatments. Ca_V1.2 substituted with the α-helix breaking proline residue were more reluctant to open than Ca_V1.2 WT but were upregulated by phosphomimetic CaM surrogates. Our results indicate that (1) CaM and its phosphomimetic analogs promote a gain in the function of Ca_V1.2 and (2) the structural properties of the first intracellular linker of Ca_V1.2 contribute to its CaM-induced modulation. We conclude that the CACNA1C clinical variant mimics the increased activity associated with the upregulation of Ca_V1.2 by Ca²⁺-CaM, thus maintaining a majority of channels in a constitutively active mode that could ultimately promote ventricular arrhythmias.