Polygenic risk score for drug-induced long QT syndrome: independent validation in a real-world patient cohort

OBJECTIVE

Drug-induced long QT syndrome (diLQTS) is an adverse reaction from over 150 FDA-approved medications, posing the risk of triggering torsades de pointes and sudden death. While common genetic variants may modestly impact QT interval individually, their collective effect can significantly amplify risk of diLQTS. Consequently, this study aimed to validate a polygenic risk score (PRS) for diLQTS previously proposed by Strauss et al .

METHODS

A retrospective cohort study was conducted utilizing patients from the Michigan Genomics Initiative prescribed 27 high-risk QT-prolonging drugs and an ECG during the prescription. The primary outcome was marked prolongation of the QTc interval (either >60 ms change from baseline or >500 ms absolute value) during treatment with a high-risk QT-prolonging drug.

RESULTS

The primary outcome occurred in 12.0% of n  = 6070 self-reported White, 12.4% of 558 African American, and 8.2% of 110 Asian patients. The PRS significantly associated with diLQTS in White patients [adjusted odds ratio = 1.44 (95% CI: 1.09-1.89); P  = 0.009]. However the study lacked sufficient statistical power to confirm the PRS as a risk factor in African Americans [adjusted odds ratio = 2.18 (95% CI: 0.98-5.49); P  = 0.073] and Asians [adjusted odds ratio = 3.21 (95% CI: 0.69-16.87); P  = 0.139] due to smaller sample sizes in these groups.

CONCLUSION

The previously published PRS for diLQTS was validated in a large, real-world cohort, demonstrating its potential as a tool for identifying high-risk patients. Incorporating this PRS into routine clinical practice could enable proactive measures to prevent life-threatening diLQTS.

Pathophysiology of syncope: current concepts and their development

Syncope is a symptom in which transient loss of consciousness occurs as a consequence of a self-limited, spontaneously terminating period of cerebral hypoperfusion. Many circulatory disturbances (e.g. brady- or tachyarrhythmias, reflex cardioinhibition-vasodepression-hypotension) may trigger a syncope or near-syncope episode, and identifying the cause(s) is often challenging. Some syncope may involve multiple etiologies operating in concert, whereas in other cases multiple syncope events may be due to various differing causes at different times. In this communication, we address the current understanding of the principal contributors to syncope pathophysiology including examination of the manner in which concepts evolved, an overview of factors that constitute consciousness and loss of consciousness, and aspects of neurovascular control and communication that are impacted by cerebral hypoperfusion leading to syncope. Emphasis focuses on 1) current understanding of the way transient systemic hypotension impacts brain blood flow and brain function; 2) the complexity and temporal sequence of vascular, humoral, and cardiac factors that may accompany the most common causes of syncope; 3) the range of circumstances and disease states that may lead to syncope; and 4) clinical features associated with syncope and in particular the reflex syncope syndromes.

miR-16-5p aggravates sepsis-associated acute kidney injury by inducing apoptosis

Sepsis-associated acute kidney injury (S-AKI) is a common disease in pediatric intensive care units (ICU) with high morbidity and mortality. The newly discovered results indicate that microRNAs (miRNAs) play an important role in the diagnosis and treatment of S-AKI and can be used as markers for early diagnosis. In this study, the expression level of miR-16-5p was found to be significantly upregulated about 20-fold in S-AKI patients, and it also increased by 1.9 times in the renal tissue of S-AKI mice. Receiver operating characteristic (ROC) curve analysis showed that miR-16-5p had the highest predictive accuracy in the diagnosis of S-AKI (AUC = 0.9188). In vitro, the expression level of miR-16-5p in HK-2 cells treated with 10 μg/mL lipopolysaccharide (LPS) increased by more than 2 times. In addition, LPS-exposed renal tissue and HK-2 cells lead to upregulation of inflammatory cytokines IL-6, IL-1β, TNF-a, and kidney damage molecules kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL). However, inhibition of miR-16-5p significantly mitigated LPS expose-mediated kidney injury and inflammation. Furthermore, LPS-exposed HK-2 cells increased more than 1.7-fold the expression levels of Bax and caspase-3, decreased 3.2-fold the expression level of B-cell lymphoma-2 (Bcl-2), and significantly promoted the occurrence of apoptosis. MiR-16-5p mimic further increased LPS-induced apoptosis in HK-2 cells. Nevertheless, inhibition of miR-16-5p significantly attenuated this effect. In summary, up-regulation of miR-16-5p expression can significantly aggravate renal injury and apoptosis in S-AKI, which also proves that miR-16-5p can be used as a potential biomarker to promote early identification of S-AKI.

Exploring the role of exosomes in the pathogenesis and treatment of cardiomyopathies: A comprehensive literature review

Exosomes, a subset of small extracellular vesicles that play a crucial role in intercellular communication, have garnered significant attention for their potential applications in the diagnosis and treatment of cardiomyopathies. Cardiomyopathies, which encompass a spectrum of heart muscle disorders, present complex challenges in diagnosis and management. Understanding the role of exosomes in the etiology of cardiomyopathies such as dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM), arrhythmogenic cardiomyopathy (AC), and hypertrophic cardiomyopathy (HCM) may open new possibilities for therapeutic intervention and diagnosis. Exosomes have indeed demonstrated promise as diagnostic biomarkers, particularly in identifying cardiac conditions such as atrial fibrillation (AF) and in the timely classification of high-risk patients with different forms of cardiomyopathy. In DCM, exosomes have been implicated in mediating pathological responses in cardiomyocytes, potentially exacerbating disease progression. Moreover, in RCM, AC, and HCM, exosomes present significant potential as diagnostic biomarkers and therapeutic targets, offering insights into disease pathogenesis and potential avenues for intervention. Understanding the influence of exosomes on disease progression and identifying the specific molecular pathways involved in cardiomyopathy pathogenesis may significantly advance diagnostic and treatment strategies. While key findings highlight the multifaceted role of exosomes in cardiomyopathy, they also emphasize the need for further research to elucidate molecular mechanisms and translate findings into clinical practice. This review highlights the evolving landscape of exosome research in cardiomyopathies and underscores the importance of ongoing investigations to harness the full potential of exosomes in improving patient outcomes.

Catheter Ablation of Atrial Fibrillation in Infiltrative Cardiomyopathies: A Narrative Review

Atrial and ventricular arrhythmias are common in patients with Infiltrative heart diseases. This review discusses ablative techniques for arrhythmias in amyloidosis, sarcoidosis, hemochromatosis, and glycogen storage disorders, primarily focusing on atrial fibrillation (AF). A thorough literature review was conducted on the MEDLINE database to synthesize current knowledge and propose future research directions. AF is the most common arrhythmia identified in patients with amyloidosis due to cellular infiltration and atrial dilation. While catheter ablation is associated with a significantly lower rate of all-cause mortality and admission rate, conflicting data exist regarding the higher risk of pericardial effusion, in-hospital mortality, length of stay, and cost of hospitalization. Cardiac sarcoid predisposes AF due to granulomas, atrial dilation, and scarring. Studies demonstrate encouraging outcomes and low recurrence rates in these patients who undergo ablation for AF, with no difference in complications compared to those without sarcoidosis. AF is the most common arrhythmia in hereditary hemochromatosis (HH), secondary to increased myocardial iron stores and elevated oxidative stress, and is primarily managed by chelation. Scant reports regarding ablation are described for HH and glycogen storage disorders. Catheter ablation is a safe and effective modality for the treatment of AF in infiltrative cardiomyopathy. Future large-scale trials are needed to confirm these findings.

Beneficial normalization of cardiac repolarization by carnitine in transgenic short QT syndrome type 1 rabbit models

AIMS

Short QT syndrome type 1 (SQT1) is a genetic channelopathy caused by gain-of-function variants in human-ether-a-go-go (HERG) underlying the rapid delayed-rectifier K+ current (IKr), leading to QT-shortening, ventricular arrhythmias, and sudden cardiac death. Data on efficient pharmacotherapy for SQT1 are scarce. In patients with primary carnitine-deficiency, acquired-short QT syndrome (SQTS) has been observed and rescued by carnitine supplementation. Here, we assessed whether carnitine exerts direct beneficial (prolonging) effects on cardiac repolarization in genetic SQTS.

METHODS AND RESULTS

Adult wild-type (WT) and transgenic SQT1 rabbits (HERG-N588K, gain of IKr) were used. In vivo electrocardiograms (ECGs), ex vivo monophasic action potentials (APs) in Langendorff-perfused hearts, and cellular ventricular APs and ion currents were assessed at baseline and during L-Carnitine/C16-Carnitine-perfusion. Two-dimensional computer simulations were performed to assess re-entry-based ventricular tachycardia-inducibility. L-Carnitine/C16-Carnitine prolonged QT-intervals in WT and SQT1, leading to QT-normalization in SQT1. Similarly, monophasic and cellular AP duration (APD) was prolonged by L-Carnitine/C16-Carnitine in WT and SQT1. As underlying mechanisms, we identified acute effects on the main repolarizing ion currents: IKr-steady, which is pathologically increased in SQT1, was reduced by L-Carnitine/C16-Carnitine and deactivation kinetics were accelerated. Moreover, L-Carnitine/C16-Carnitine decreased IKs-steady and IK1. In silico modelling identified IKr changes as the main factor for L-Carnitine/C16-Carnitine-induced APD-prolongation. 2D simulations revealed increased sustained re-entry-based arrhythmia formation in SQT1 compared to WT, which was decreased to the WT-level when adding carnitine-induced ion current changes.

CONCLUSION

L-Carnitine/C16-Carnitine prolong/normalize QT and whole-heart/cellular APD in SQT1 rabbits. These beneficial effects are mediated by acute effects on IKr. L-Carnitine may serve as a potential future QT-normalizing, anti-arrhythmic therapy in SQT1.

Clinical Features and Outcomes of Pediatric MYH7-Related Dilated Cardiomyopathy

BACKGROUND

Although genetic variants in MYH7 are the most frequent cause of pediatric genetic dilated cardiomyopathy (DCM), there are no studies available describing this entity. We sought to describe clinical features, analyze variant location, and explore predictors of bad prognosis in pediatric MYH7-related DCM.

METHODS AND RESULTS

We evaluated clinical records from 44 patients (24 men; median age at diagnosis, 0.54 [interquartile range, 0.01-10.8] years) with pathogenic/likely pathogenic variants in MYH7 diagnosed with DCM at pediatric age (<18 years) followed at 13 international centers. We also explored risk factors associated with a composite end point of end-stage heart failure defined as heart transplantation or heart failure-related death. Twenty-two patients (50%) were diagnosed at age <6 months, including 7 (16%) at birth. Left ventricular (LV) hypertrabeculation features were present in 15 (38%), particularly among patients with genetic variants in the head domain. After a median follow-up of 6.1 years (interquartile range, 1.9-13.4), 15 patients (36%) required a heart transplant (n=14) or died due to end-stage heart failure (n=1), 15 patients (36%) persisted with systolic dysfunction despite treatment, 12 (29%) had a significant increase in LV ejection fraction, and 2 were lost to follow-up. Overall, end-stage heart failure event rate was 25% at 5 years. New York Heart Association class III to IV (hazard ratio [HR], 7.67 [95% CI, 2.16-27.2]; P=0.002) and LV ejection fraction ≤35% (HR, 4.00 [95% CI, 1.11-14.4]; P=0.03) were the best predictors of bad prognosis.

CONCLUSIONS

Pediatric MYH7-related DCM is characterized by early onset, frequent LV hypertrabeculation, and poor prognosis. Advanced New York Heart Association class and low LV ejection fraction emerged as predictors of end-stage heart failure.

Promise and Peril of a Genotype-First Approach to Mendelian Cardiovascular Disease

Precision medicine, which among other aspects includes an individual's genomic data in diagnosis and management, has become the standard-of-care for Mendelian cardiovascular disease (CVD). However, early identification and management of asymptomatic patients with potentially lethal and manageable Mendelian CVD through screening, which is the promise of precision health, remains an unsolved challenge. The reduced costs of genomic sequencing have enabled the creation of biobanks containing in-depth genetic and health information, which have facilitated the understanding of genetic variation, penetrance, and expressivity, moving us closer to the genotype-first screening of asymptomatic individuals for Mendelian CVD. This approach could transform health care by diagnostic refinement and facilitating prevention or therapeutic interventions. Yet, potential benefits must be weighed against the potential risks, which include evolving variant pathogenicity assertion or identification of variants with low disease penetrance; costly, stressful, and inappropriate diagnostic evaluations; negative psychological impact; disqualification for employment or of competitive sports; and denial of insurance. Furthermore, the natural history of Mendelian CVD is often unpredictable, making identification of those who will benefit from preventive measures a priority. Currently, there is insufficient evidence that population-based genetic screening for Mendelian CVD can reduce adverse outcomes at a reasonable cost to an extent that outweighs the harms of true-positive and false-positive results. Besides technical, clinical, and financial burdens, ethical and legal aspects pose unprecedented challenges. This review highlights key developments in the field of genotype-first approaches to Mendelian CVD and summarizes challenges with potential solutions that can pave the way for implementing this approach for clinical care.

Coenzyme Q deficiency may predispose to sudden unexplained death via an increased risk of cardiac arrhythmia

Cardiac arrhythmia is currently considered to be the direct cause of death in a majority of sudden unexplained death (SUD) cases, yet the genetic predisposition and corresponding endophenotypes contributing to SUD remain incompletely understood. In this study, we aimed to investigate the involvement of Coenzyme Q (CoQ) deficiency in SUD. First, we re-analyzed the exome sequencing data of 45 SUD and 151 sudden infant death syndrome (SIDS) cases from our previous studies, focusing on previously overlooked genetic variants in 44 human CoQ deficiency-related genes. A considerable proportion of the SUD (38%) and SIDS (37%) cases were found to harbor rare variants with likely functional effects. Subsequent burden testing, including all rare exonic and untranslated region variants identified in our case cohorts, further confirmed the existence of significant genetic burden. Based on the genetic findings, the influence of CoQ deficiency on electrophysiological and morphological properties was further examined in a mouse model. A significantly prolonged PR interval and an increased occurrence of atrioventricular block were observed in the 4-nitrobenzoate induced CoQ deficiency mouse group, suggesting that CoQ deficiency may predispose individuals to sudden death through an increased risk of cardiac arrhythmia. Overall, our findings suggest that CoQ deficiency-related genes should also be considered in the molecular autopsy of SUD.

Prognostic significance of electrophysiological study in drug-induced type-1 Brugada syndrome: a brief systematic review

BACKGROUND

Risk stratification in drug-induced type-1 Brugada syndrome (BrS) patients is challenging. The role of electrophysiological study (EPS) is debated as the majority of drug-induced type-1 BrS patients would not be studied according to the latest recommendations.

METHODS

A complete systematic literature search was performed to gauge the EPS role in this population. Three subgroups were defined: positive-EPS group, negative-EPS group, no-EPS group.

RESULTS

Among 1318 drug-induced type-1 BrS patients, no significant difference in the incidence rate of arrhythmic events was observed between groups (I2 = 45%, P for subgroup difference = 0.10) during a mean follow-up of 5.1 years, also considering symptomatic status.

CONCLUSION

In long-term follow-up of drug-induced type-1 BrS patients, EPS does not seem to aid prognostic stratification.

Molecular autopsy in Chinese sudden cardiac death in the young

Inherited cardiovascular conditions are significant causes of sudden cardiac death in the young (SCDY), making their investigation using molecular autopsy and prevention a public health priority. However, the molecular autopsy data in Chinese population is lacking. The 5-year result (2017-2021) of molecular autopsy services provided for victims of SCDY (age 1-40 years) was reviewed. The outcome of family cascade genetic screening and clinical evaluation was reviewed. A literature review of case series reporting results of molecular autopsy on SCDY in 2016-2023 was conducted. Among the 41 decedents, 11 were found to carry 13 sudden cardiac death (SCD)-causative genetic variants. Likely pathogenic (LP) variants were identified in the DSP, TPM1, TTN, and SCN5A genes. Cascade genetic testing identified four family members with LP variants. One family member with familial TPM1 variant was found to have hypertrophic cardiomyopathy upon clinical evaluation. This study provided insight into the genetic profile of molecular autopsy in a Chinese cohort of SCDY. The detection of important SCD-causative variants through molecular autopsy has facilitated family cascade screening by targeted genetic testing and clinical evaluation of at-risk family members. A literature review of the current landscape of molecular autopsy in the investigation of SCDY was conducted.

Dilated cardiomyopathy due to a novel combination of TTN and BAG3 genetic variants: From acute heart failure to subclinical phenotypes

Dilated cardiomyopathy (DCM) is defined as left ventricular enlargement accompanied by systolic dysfunction not explained by abnormal loading conditions or coronary heart disease. The DCM clinical spectrum is broad, ranging from subclinical to severe presentation with progression to end stage heart failure. To date, different genetic loci have been found to have moderate/definitive evidence for causality in DCM and pathogenic variants in the TTN gene represent the main genetic determinant. Here, we describe a family in which the co-occurrence of two genetic hits, one in the TTN and one in the BAG3 gene, was associated with heterogeneous clinical presentation ranging from subclinical phenotypes to acute cardiogenic shock mimicking fulminant myocarditis. We hypothesize that at least some specific BAG3 genotypes could be related to DCM presenting with acute heart failure and suggest that patients and relatives carrying BAG3 pathogenic variants should be addressed to a tertiary-level heart care center.

Cardiomyopathy: pathogenesis and therapeutic interventions

Cardiomyopathy is a group of disease characterized by structural and functional damage to the myocardium. The etiologies of cardiomyopathies are diverse, spanning from genetic mutations impacting fundamental myocardial functions to systemic disorders that result in widespread cardiac damage. Many specific gene mutations cause primary cardiomyopathy. Environmental factors and metabolic disorders may also lead to the occurrence of cardiomyopathy. This review provides an in-depth analysis of the current understanding of the pathogenesis of various cardiomyopathies, highlighting the molecular and cellular mechanisms that contribute to their development and progression. The current therapeutic interventions for cardiomyopathies range from pharmacological interventions to mechanical support and heart transplantation. Gene therapy and cell therapy, propelled by ongoing advancements in overarching strategies and methodologies, has also emerged as a pivotal clinical intervention for a variety of diseases. The increasing number of causal gene of cardiomyopathies have been identified in recent studies. Therefore, gene therapy targeting causal genes holds promise in offering therapeutic advantages to individuals diagnosed with cardiomyopathies. Acting as a more precise approach to gene therapy, they are gradually emerging as a substitute for traditional gene therapy. This article reviews pathogenesis and therapeutic interventions for different cardiomyopathies.

Intraoperative QTc interval interpretation: Effects of anaesthesia, ECG, correction formulae, sex, and current limits: A Prospective Observational Study

BACKGROUND

Severe QT interval prolongation requires monitoring QTc intervals during anaesthesia with recommended therapeutic interventions at a threshold of 500 ms. The need for 12-lead ECG and lack of standardisation limit such monitoring. We determined whether automated continuous intraoperative QTc monitoring with 5-lead ECG measures QTc intervals comparable to 12-lead ECG and whether the interpretation of QTc intervals depends on the correction formulae and the patient's sex. We compared intraoperative QTc times to QTc times from resting ECGs of a population from the same region, to substantiate the hypothesis that patients under general anaesthesia may need specific treatment thresholds.

METHODS

In this prospective observational study, intraoperative QT/QTc intervals were automatically recorded using 12 and 5-lead ECG in 100 patients (44% males). QTc values were analysed for sex and formula-specific aspects after correction for heart rate according to Bazett, Fridericia, Hodges, Framingham, Charbit and QTcRAS, and compared to a regional community-based cohort. The level of significance was set to α = 0.05.

RESULTS

QT interval duration was not significantly different between 12-lead and 5-lead ECG (difference - 0.09 ms ± 8.5 ms, p = 0.793). The QTc interval duration significantly differed between the correction formulae (p < 0.001) and between sexes (p < 0.001). Mean intraoperative QTc duration was higher than in resting ECGs from a large community-based population with the same regional background (438 vs. 417 ms). The incidence of prolonged values >500 ms significantly depended on the correction formula (p < 0.001) and was up to tenfold higher in women versus men.

CONCLUSION

Intraoperative QTc interval measurement using a 5-lead ECG is valid. Correction formulae and gender influence the intraoperative QTc interval duration and the incidence of pathologically prolonged values according to current limits. The consideration and definition of sex-specific normal limits for QTc times under general anaesthesia, therefore, warrant further investigation.

Concealed cardiomyopathy as an emerging cause of sudden cardiac arrest and sudden cardiac death

The inherited cardiomyopathies exhibit a broad spectrum of disease, with some patients remaining asymptomatic throughout life, while, for others, the first symptom of disease is sudden cardiac death at a young age. The risk of malignant ventricular arrhythmia in these conditions has traditionally been linked to the degree of structural myocardial abnormalities and functional impairment. However, recent advances in genetic testing and knowledge of the genetic basis of the diseases have led to the identification of concealed cardiomyopathy, in which sudden cardiac arrest or sudden cardiac death occurs in the absence of observable clinical features of cardiomyopathy, with a diagnosis being made only after the identification of a causative genetic variant. Increased awareness of concealed cardiomyopathy, a better understanding of mechanisms of arrhythmia and identification of risk modulators will be vital to improve care for families with concealed cardiomyopathy.

Cardiac channelopathies in pediatrics: a genetic update

Cardiac channelopathies are a group of inherited syndromes that can cause malignant arrhythmias and sudden cardiac death, particularly in the pediatric population. Today, a 12-lead electrocardiogram is the most effective tool to diagnose these diseases. Incomplete penetrance and variable expressivity are hallmarks of these syndromes. Some of these malignant entities may remain hidden and only a trigger such as exercise, emotions or fever can unmask the electrical pattern to diagnose the disease. Sudden cardiac death may be the first manifestation of any of these syndromes. The use of complementary tests that allow early diagnosis is strongly recommended, among which we find: pharmacological provocations, exercise tests, and genetic analysis. Genetic testing makes it possible to unravel the origin of the disease, and also identify family members who carry the harmful genetic defect and are therefore at risk. One of the main challenges in this area is the large number of genetic variants of uncertain significance, which prevent effective translation into clinical practice. Early identification of the pediatric population at risk and adequate risk stratification are crucial to adopting personalized preventive measures that reduce the risk of lethal episodes in this population. What is Known: • In the pediatric population, malignant arrhythmias leading to sudden cardiac death are mainly caused by inherited syndromes. • A conclusive genetic diagnosis unravels the origin of the syndrome and allows cascade screening to identify relatives carrying the genetic alteration. What is New: • The use of sequencing technologies allows a broad genetic analysis, helping to unravel new genetic alterations causing inherited arrhythmogenic syndromes. • A periodic reanalysis of genetic variants that currently have an ambiguous role will help discern those that are truly pathogenic.

Investigating cardiac genetic background in sudden infant death syndrome (SIDS)

Sudden infant death syndrome (SIDS) is still the leading cause of death for newborns in developed countries. The pathophysiological mechanisms have not been fully clarified, but in some of SIDS cases variants of genes associated with inherited cardiac conditions are found. In this study, an analysis of SCD-related genes was performed to determine the prevalence of rare pathogenic (P) or likely pathogenic (LP) variants that could provide an unambiguous explanation for the fatal event. A cohort of 76 SIDS cases underwent Next-Generation Sequencing (NGS) analysis with a custom panel of SCD-related genes. Rare variants were classified according to the guidelines provided by the American College of Medical Genetics and Genomics (ACMG) and the specifications of the ClinGen association. Post-mortem genetic testing identified 50 (65.8%) carriers of at least one variant in SCD genes. 104 rare genetic variants were found, 65.4% in genes encoding structural proteins. Only 4 out of 76 cases (5.3%) hosted at least a P or LP variant found in genes with structural or structural/arrhythmogenic functions (SLC22A5, SCN5A, MYL3and TTN). 99 variants were classified as of uncertain significance (VUS). The difference in the distribution of variants between gene groups by function was not statistically significant (chi square, p = 0,219). Despite this, most of the variants concerned structural genes that were supposed to have a close interaction with ion channels, thus providing an explanation for the arrhythmic event. Segregation analysis, reclassification of VUS variants and identification of new associated genes could clarify the implications of the current findings.

Genetic Polymorphism in miRNA Genes and Their Association with susceptibility of Coronary Heart Disease: anAn Updated Rreview

Coronary heart disease (CHD) remains a major public health concern worldwide, with a complex interplay of genetic, environmental and lifestyle factors contributing to its pathogenesis. The potential significance of microRNAs (miRNAs) in the onset and progression of CHD has attracted increasing attention in recent years. Small non-coding RNA molecules called miRNAs control gene expression at the post-transcriptional level. Dysregulation of miRNAs has been linked to a variety of biological processes, including cell division, proliferation, apoptosis, and inflammation. Numerous research studies have looked into the relationship between genetic variants in miRNA genes and CHD susceptibility. This review highlights the recent research work carried out to identify the relationship of miRNA genes polymorphism with the progression and susceptibility of CHD. Such studies could pave the way for the development of personalized strategies for CHD prevention and treatment based on an individual's genetic profile.

Automated variant re-evaluation is labor-balanced and gives clinically relevant results: Hereditary cardiac disease as a use case

BACKGROUND

Genetic findings influence clinical care of patients suspected of hereditary cardiac diseases. As additional knowledge arises over time, the classification of genetic variants may change. The labor cost associated with systematic manual reevaluation for reported variants is substantial. We applied an automated variant classifier for reevaluation of previous reported variants to assess how such tools may assist in manual reevaluation.

METHODS

Historically (2010-2022), patients (N = 2987) suspected of inherited cardiomyopathies or ion-channel disorders were screened for genetic variants in at least one of up to 114 genes. We had reported 1455 unique variants, of which 742 were among the 14 most relevant genes. In the 14-gene-group, we compared our reported classification to that of an autoclassifier and manually reevaluated variant classification of all variants. Among the remaining genes (N = 100), only variants where the autoclassifier predicted change of clinical impact, such as variant of uncertain significance to likely pathogenic or oppositely, were manually reevaluated.

RESULTS

We identified 9% (66/742) of variants with clinical impact in the 14-gene-group. Of these, 91% could have been identified solely evaluating the 120 variants where the autoclassifier had predicted a change of clinical impact. In the 100 remaining genes, a change of clinical impact was identified in 3% (22/713) after manual reevaluation.

CONCLUSION

Using an autoclassifier reduces the workload to identify variants likely to have a change in variant class with clinical impact. Hence, we recommend using such tools to identify the variants most relevant to manually reevaluate to improve patient care.

The many faces of SCN5A pathogenic variants: from channelopathy to cardiomyopathy

The SCN5A gene encodes the alpha subunit of the cardiac sodium channel, which plays a fundamental role in the generation and propagation of the action potential in the heart muscle. During the past years our knowledge concerning the function of the cardiac sodium channel and the diseases caused by mutations of the SCN5A gene has grown. Although initially SCN5A pathogenic variants were mainly associated with channelopathies, increasing recent evidence suggests an association with structural heart disease in the form of heart muscle disease. The pathways leading to a cardiomyopathic phenotype remain unclear and require further elucidation. The aim of the present review is to provide a concise summary regarding the mechanisms through which SCN5A pathogenic variants result in heart disease, focusing in cardiomyopathy, highlighting along the way the complex role of the SCN5A gene at the intersection of cardiac excitability and contraction networks.

Morphological phenotype of right ventricular outflow tract is associated with cardiovascular outcomes and premature death

Morphology of right ventricular outflow tract (RVOT) is potentially related to cardiovascular outcomes. However, this relationship still remains to be verified with direct evidence. We retrospectively reviewed cases from the autopsy specimen library in the Center of Forensic Medicine in Sun Yat-sen University from 2017 to 2023. Six RVOT morphological characteristics were measured and their association with cardiovascular diseases (CVDs), sudden cardiac death (SCD) and age at death was evaluated. Relationship between myocardial fibrosis in RVOT and CVDs was investigated. RVOT characteristics were recruited by machine learning algorithms for diagnosing CVDs. A total of 2370 cases were finally recruited. Perimeter of sub-valve plane (pSBV) in RVOT was positively associated with risk of CVDs and SCD (OR: 1.21, 95%CI: 1.07-1.37, p = 0.003; OR: 1.33, 95%CI: 1.16-1.52, p < 0.001). Compared with thickness of septum (tS) < 3.0 mm, tS ≥ 3.0 mm was associated with premature death in disease-dominant death (β=-0.16, 95%CI: -0.20 to -0.11, p < 0.001) and SCD (β=-0.15, 95%CI: -0.21 to -0.10, p < 0.001). Degree of myocardial fibrosis in the posterior septum was increased in coronary atherosclerosis (6.86%±2.48% vs. 4.91%±2.14%, p = 0.011) and cardiomyopathies (8.11%±3.24% vs. 4.88%±3.11%, p = 0.005). A logistic regression model, recruiting age, left and right ventricular wall thickness, pSBV, circumference of pulmonary annulus and aortic annulus, was elected as an optimal diagnostic model of CVDs, yielding AUC of 0.734 (95%CI: 0.705-0.763), 0.781 (0.740-0.821) and 0.763 (0.725-0.800) in training, validation and test sets. Increased pSBV significantly correlates with higher risk of CVDs and SCD. And tS ≥ 3.0 mm is an independent risk factor of premature death regardless of diseases.

CardioGraph: a platform to study variations associated with familiar cardiopathies

BACKGROUND

Familiar cardiopathies are genetic disorders that affect the heart. Cardiologists face a significant problem when treating patients suffering from these disorders: most DNA variations are novel (i.e., they have not been classified before). To facilitate the analysis of novel variations, we present CardioGraph, a platform specially designed to support the analysis of novel variations and help determine whether they are relevant for diagnosis. To do this, CardioGraph identifies and annotates the consequence of variations and provides contextual information regarding which heart structures, pathways, and biological processes are potentially affected by those variations.

METHODS

We conducted our work through three steps. First, we define a data model to support the representation of the heterogeneous information. Second, we instantiate this data model to integrate and represent all the genomics knowledge available for familiar cardiopathies. In this step, we consider genomic data sources and the scientific literature. Third, the design and implementation of the CardioGraph platform. A three-tier structure was used: the database, the backend, and the frontend.

RESULTS

Three main results were obtained: the data model, the knowledge base generated with the instantiation of the data model, and the platform itself. The platform code has been included as supplemental material in this manuscript. Besides, an instance is publicly available in the following link: https://genomics-hub.pros.dsic.upv.es:3090 .

CONCLUSION

CardioGraph is a platform that supports the analysis of novel variations. Future work will expand the body of knowledge about familiar cardiopathies and include new information about hotspots, functional studies, and previously reported variations.

NaV1.5 autoantibodies in Brugada syndrome: pathogenetic implications

BACKGROUND AND AIMS

Patients suffering from Brugada syndrome (BrS) are predisposed to life-threatening cardiac arrhythmias. Diagnosis is challenging due to the elusive electrocardiographic (ECG) signature that often requires unconventional ECG lead placement and drug challenges to be detected. Although NaV1.5 sodium channel dysfunction is a recognized pathophysiological mechanism in BrS, only 25% of patients have detectable SCN5A variants. Given the emerging role of autoimmunity in cardiac ion channel function, this study explores the presence and potential impact of anti-NaV1.5 autoantibodies in BrS patients.

METHODS

Using engineered HEK293A cells expressing recombinant NaV1.5 protein, plasma from 50 BrS patients and 50 controls was screened for anti-NaV1.5 autoantibodies via western blot, with specificity confirmed by immunoprecipitation and immunofluorescence. The impact of these autoantibodies on sodium current density and their pathophysiological effects were assessed in cellular models and through plasma injection in wild-type mice.

RESULTS

Anti-NaV1.5 autoantibodies were detected in 90% of BrS patients vs. 6% of controls, yielding a diagnostic area under the curve of .92, with 94% specificity and 90% sensitivity. These findings were consistent across varying patient demographics and independent of SCN5A mutation status. Electrophysiological studies demonstrated a significant reduction specifically in sodium current density. Notably, mice injected with BrS plasma showed Brugada-like ECG abnormalities, supporting the pathogenic role of these autoantibodies.

CONCLUSIONS

The study demonstrates the presence of anti-NaV1.5 autoantibodies in the majority of BrS patients, suggesting an immunopathogenic component of the syndrome beyond genetic predispositions. These autoantibodies, which could serve as additional diagnostic markers, also prompt reconsideration of the underlying mechanisms of BrS, as evidenced by their role in inducing the ECG signature of the syndrome in wild-type mice. These findings encourage a more comprehensive diagnostic approach and point to new avenues for therapeutic research.

Prevalence and associated factors of ECG abnormality patterns indicative of cardiac channelopathies among adult general population of Tehran, Iran: a report from the Tehran Cohort Study (TeCS)

BACKGROUND

The characteristics of electrocardiogram (ECG) abnormalities related to cardiac channelopathies potentially linked to sudden cardiac death (SCD) are not widely recognized in Iran. We examined the prevalence of such ECG patterns and their related factors among adult residents of Tehran, Iran.

METHODS

The clinical characteristics and 12-lead ECGs of Tehran Cohort Study participants were examined. Long QT intervals, short QT intervals, Brugada syndrome (BrS) patterns, and early repolarization (ER) were evaluated using computer-based assessment software validated by cardiologists. Logistic regression models were employed to identify the factors associated with the prevalence of different ECG patterns.

RESULTS

Out of 7678 available ECGs, 7350 were included in this analysis. Long QT interval, ER pattern, BrS patterns, and short QT interval were found in 3.08%, 1.43%, 0.31%, and 0.03% of participants, respectively. The prevalence of long QT interval increased with age, opium consumption, and presence of hypertension. Younger age, lower body mass index (BMI), alcohol use and male sex were independently linked to an elevated prevalence of ER pattern. Most individuals with BrS patterns were men (95%) and had lower BMI, high- and low-density lipoprotein, and total cholesterol compared to those without the BrS pattern. At a mean follow-up of 30.2 ± 5.5 months, all-cause mortality in the group exhibiting abnormal ECG patterns (6.3%) was approximately twice as high as that in the group without such patterns (2.96%).

CONCLUSION

Abnormal ECG patterns corresponding to channelopathies were relatively rare among adult residents of the Tehran population, and their prevalence was influenced by various factors.

CLINICAL TRIAL NUMBER

Not applicable.

Exploration of the potential association between newer antiseizure medications and arrhythmias: Integrating pharmacovigilance and bioinformatics evidence

INTRODUCTION

Arrhythmias resulting from newer antiseizure medications (ASMs) may significantly impact the safety and quality of life of patients with epilepsy. This study investigated the potential association between new first-line or second-line ASMs and arrhythmias.

METHODS

Pharmacovigilance analysis was conducted using data from the Food and Drug Administration Adverse Event Reporting System (FAERS) from 2004 to 2023. A disproportionality analysis was performed to compare newer ASMs with other drugs, using carbamazepine and valproate as positive controls. Newer ASMs were categorized into sodium channel (SCN) main mechanism, SCN possible mechanism, and non-SCN group. The bioinformatics analysis involved retrieving therapeutic gene targets for ASMs from the DrugBank and OMIM databases, as well as identifying arrhythmia disease targets from the GeneCards database. Additionally, enrichment analysis of gene ontology functions and KEGG pathways was conducted.

RESULTS

A total of 3,457 cases of arrhythmias associated with newer ASMs were identified in the FAERS database. Disproportionality analysis indicates that brivaracetam (IC025 = 0.08), zonisamide (IC025 = 0.13), eslicarbazepine (IC025 = 0.39), and lacosamide (IC025 = 0.84) exhibited a positive signal for arrhythmias, with signals predominantly observed in the SCN main mechanism group. Furthermore, bioinformatics analysis revealed the involvement of adrenergic signaling in cardiac myocytes, as well as the participation of sodium channel genes in ASM-induced arrhythmias.

CONCLUSION

Our findings suggest a potential association between SCN-ASMs and arrhythmias, highlighting the importance of monitoring and evaluating the safety profiles of newer ASMs in clinical practice. Further research is necessary to elucidate the underlying mechanisms and inform patient care strategies.

Effects of Anesthesia with Pentobarbital/Ketamine on Mitochondrial Permeability Transition Pore Opening and Ischemic Brain Damage

BACKGROUND AND OBJECTIVE

The alteration of mitochondrial functions, especially the opening of the mitochondrial permeability transition pore (mPTP), has been proposed as a key mechanism in the development of lesions in cerebral ischemia, wherefore it is considered as an important target for drugs against ischemic injury. In this study, we aimed to investigate the effects of mitochondrial complex I inhibitors as possible regulators of mPTP using an in vitro brain ischemia model of the pentobarbital/ketamine (PBK)-anesthetized rats.

RESULTS

We found that PBK anesthesia itself delayed Ca2+-induced mPTP opening and partially recovered the respiratory functions of mitochondria, isolated from rat brain cortex and cerebellum. In addition, PBK reduced cell death in rat brain slices of cerebral cortex and cerebellum. PBK inhibited the adenosine diphosphate (ADP)-stimulated respiration of isolated cortical and cerebellar mitochondria respiring with complex I-dependent substrates pyruvate and malate. Moreover, pentobarbital alone directly increased the resistance of isolated cortex mitochondria to Ca2+-induced activation of mPTP and inhibited complex I-dependent respiration and mitochondrial complex I activity. In contrast, ketamine had no direct effect on functions of isolated normal cortex and cerebellum mitochondria.

CONCLUSIONS

Altogether, this suggests that modulation of mitochondrial complex I activity by pentobarbital during PBK anesthesia may increase the resistance of mitochondria to mPTP opening, which is considered the key event in brain cell necrosis during ischemia.

Network Pharmacology Approaches Used to Identify Therapeutic Molecules for Chronic Venous Disease Based on Potential miRNA Biomarkers

Chronic venous disease (CVD) is a prevalent condition in adults, significantly affecting the global elderly population, with a higher incidence in women than in men. The modulation of gene expression through microRNA (miRNA) partly regulated the development of cardiovascular disease (CVD). Previous research identified a functional analysis of seven genes (CDS2, HDAC5, PPP6R2, PRRC2B, TBC1D22A, WNK1, and PABPC3) as targets of miRNAs related to CVD. In this context, miRNAs emerge as essential candidates for CVD diagnosis, representing novel molecular and biological knowledge. This work aims to identify, by network analysis, the miRNAs involved in CVD as potential biomarkers, either by interacting with small molecules such as toxins and pollutants or by searching for new drugs. Our study shows an updated landscape of the signaling pathways involving miRNAs in CVD pathology. This latest research includes data found through experimental tests and uses predictions to propose both miRNAs and genes as potential biomarkers to develop diagnostic and therapeutic methods for the early detection of CVD in the clinical setting. In addition, our pharmacological network analysis has, for the first time, shown how to use these potential biomarkers to find small molecules that may regulate them. Between the small molecules in this research, toxins, pollutants, and drugs showed outstanding interactions with these miRNAs. One of them, hesperidin, a widely prescribed drug for treating CVD and modulating the gene expression associated with CVD, was used as a reference for searching for new molecules that may interact with miRNAs involved in CVD. Among the drugs that exhibit the same miRNA expression profile as hesperidin, potential candidates include desoximetasone, curcumin, flurandrenolide, trifluridine, fludrocortisone, diflorasone, gemcitabine, floxuridine, and reversine. Further investigation of these drugs is essential to improve the treatment of cardiovascular disease. Additionally, supporting the clinical use of miRNAs as biomarkers for diagnosing and predicting CVD is crucial.

Clinical and genetic profile of Chinese children with Danon disease: A single-center retrospective cohort study

BACKGROUND

Danon disease (DD) is a rare X-linked dominant lysosomal storage disorder. Studies on DD pediatric patients are limited due to the small number of cases and challenges in early detection.

METHODS

We retrospectively analyzed clinical and genetic data of 29 pediatric patients who visited our hospital for treatment or genetic counseling of DD from July 2014 to December 2023.

RESULTS

The mean age at diagnosis was 7.2±5.9 years for males (n=21) and 9.4±5.0 years for females (n=8). Asymptomatic elevated liver aminotransferase and/or creatine kinase (CK) levels were initial manifestations detected in 10 (48%) male patients and absent in female patients. Hypertrophic cardiomyopathy (HCM) was observed in 20 (95%) male and 7 (88%) female patients, while dilated cardiomyopathy (DCM) was not detected. Ventricular preexcitation (VP) was observed initially in 10 (36%) patients and in 15 (54%) at latest evaluation. Patients with VP had higher left ventricular posterior wall thickness in diastole z-scores than those without VP (5.6±2.2 vs. 3.5±2.1, p=0.029). During a median 2.7-years follow-up, two males received heart transplants. One boy and one girl died of heart failure and sudden cardiac arrest, respectively. Twenty-three pathogenic LAMP2 variants were identified, including seven novel variants.

CONCLUSIONS

A retrospective review of 29 DD cases suggests an underrecognized asymptomatic period in male DD patients, characterized by elevations in serum CK and transaminases. HCM appears to be the only cardiac manifestation in pediatric female patients, unlike a high incidence of DCM in adult female patients. The incidence of VP may increase with disease progression.

Novel associations between KCNQ1 rs231840 polymorphism and preeclampsia in Chinese gestational women: A case-control candidate genetic study

Preeclampsia is a complex disorder with genetic and environmental interactions. In this study, we analyzed the associations of KCNQ1gene polymorphisms with preeclampsia in Chinese pregnant women. The 3 candidate single-nucleotide polymorphisms rs231840, rs2237892, and rs2237895 were genotyped in this case-control study; clinical and biochemical data were included and SNPs were gathered from 248 individuals with preeclampsia and 237 controls. The TT genotype rs231840 increased the risk of preeclampsia (OR: 1.633; 95% CI: 1.027-2.597) and was associated with higher blood glucose levels. The haplotype TCA containing the allele of rs231840 (T), rs2237892 (C), and rs2237895 (A) was highly protective against preeclampsia and associated with the levels of blood glucose in preeclamptic patients. A novel function was found for the haplotype CCA in SNPs rs231840 (C), rs2237892 (C), and rs2237895 (A); it might be a protective combination against preeclampsia. The KCNQ1 (TT) genotype seems to be associated with preeclampsia and might affect the regulation of blood glucose in Chinese pregnant women.

Pathophysiology of dilated cardiomyopathy: from mechanisms to precision medicine

Dilated cardiomyopathy (DCM) is a complex disease with multiple causes and various pathogenic mechanisms. Despite improvements in the prognosis of patients with DCM in the past decade, this condition remains a leading cause of heart failure and premature death. Conventional treatment for DCM is based on the foundational therapies for heart failure with reduced ejection fraction. However, increasingly, attention is being directed towards individualized treatments and precision medicine. The ability to confirm genetic causality is gradually being complemented by an increased understanding of genotype-phenotype correlations. Non-genetic factors also influence the onset of DCM, and growing evidence links genetic background with concomitant non-genetic triggers or precipitating factors, increasing the extreme complexity of the pathophysiology of DCM. This Review covers the spectrum of pathophysiological mechanisms in DCM, from monogenic causes to the coexistence of genetic abnormalities and triggering environmental factors (the 'two-hit' hypothesis). The roles of common genetic variants in the general population and of gene modifiers in disease onset and progression are also discussed. Finally, areas for future research are highlighted, particularly novel therapies, such as small molecules, RNA and gene therapy, and measures for the prevention of arrhythmic death.

The power of hybridization capture - Illustrated using an expanded gene panel on 100 post mortem samples, focusing on sudden unexplained death

Sudden unexpected death (SUD) is an unexpected event that in many cases are caused by diseases with an underlying genetic background. Forensic molecular autopsy is an approach that has gained wide-spread attention, in part explained by the rapid progress of DNA sequencing techniques. The approach leverages genetic data in combination with medical autopsy findings in post-mortem samples to explore a potential underlying genetic cause of death. Traditional forensic approaches to molecular autopsy focus on a small panel of genes, say <200 genes, with strong association to heart conditions whereas clinical genetics tend to capture entire exomes while subsequently selecting targeted panels bioinformatically. The drop in price and the increased throughput has promoted wider exome sequencing as a viable method to discover genetic variants. We explore a targeted gene panel consisting of 2422 genes, selected based on their broad association to sudden unexplained death. A hybridization capture approach from Twist Bioscience based on double stranded DNA probes was used to target exons of the included genes. We selected and sequenced a total of 98 post-mortem samples from historical forensic autopsy cases where the cause of death could not be unambiguously determined based on medical findings and that had a previous negative molecular autopsy. In the current study, we focus on the performance of the hybridization capture technology on a 2422 gene panel and explore metrics related to sequencing success using a mid-end NextSeq 550 as well as a MiSeq FGx platform. With the latter we demonstrate that our sequence data benefits from 2×300 bp sequencing increasing coverage, in particular, for difficult regions where shadow coverage, i.e. regions outside the probes, are utilized. The results further illustrate a highly uniform capture across the panel of genes (mean fold80=1.5), in turn minimizing excessive sequencing costs to reach sufficient coverage, i.e. 20X. We outline a stepwise procedure to select genes associated with SUD through virtual bioinformatical panels extracting tier of genes with increasing strength of association to SUD. We propose some prioritization strategies to filter variants with highest potential and show that the number of high priority genetic variant requiring manual inspections is few (0-3 for all tiers of genes) when all filters are applied.

SnRNA-seq reveals differential functional transcriptional pathway alterations in three mutant types of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a leading cause of heart failure, characterized by ventricular dilation, thinning of the ventricular walls, and systolic dysfunction in either the left or both ventricles, often accompanied by fibrosis. Human cardiac tissue is composed of various cell types, including cardiomyocytes (CMs), fibroblasts (FBs), endothelial cells (ECs), macrophages, lymphocytes and so on. In DCM patients, these cells frequently undergo functional and phenotypic changes, contributing to contractile dysfunction, inflammation, fibrosis, and cell death, thereby increasing the risk of heart failure. This study focuses on DCM patients with mutations (LMNA, RBM20, and TTN) and analyzes functional changes in subpopulations of four cardiac cell types. The study involves functional annotation of subpopulations within each cell type and explores the association between gene mutations and specific functions and pathways. Additionally, the SCENIC method is employed of a particular cell subpopulation with significant functional importance, aiming to identify key transcriptional regulators in specific cell states. By analyzing the expression levels of ligand-receptor pairs in vCM4, vFB2, EC5.0, T cells, and NK cells across the DCM mutant genotypes, we predicted their signaling pathways and communications. This research provides insights into the molecular mechanisms of DCM and potential therapeutic targets.

Clinically relevant mouse models of severe spinal muscular atrophy with respiratory distress type 1

Spinal Muscular Atrophy with Respiratory Distress (SMARD1) is a lethal infantile disease, characterized by the loss of motor neurons leading to muscular atrophy, diaphragmatic paralysis, and weakness in the trunk and limbs. Mutations in IGHMBP2, a ubiquitously expressed DNA/RNA helicase, have been shown to cause a wide spectrum of motor neuron disease. Though mutations in IGHMBP2 are mostly associated with SMARD1, milder alleles cause the axonal neuropathy, Charcot-Marie-Tooth disease type 2S (CMT2S), and some null alleles are potentially a risk factor for sudden infant death syndrome (SIDS). Variant heterogeneity studied using an allelic series can be informative in order to create a broad spectrum of models that better exhibit the human variation. We previously identified the nmd2J mouse model of SMARD1, as well as two milder CMT2S mouse models. Here, we used CRISPR-Cas9 genome editing to create three new, more severe Ighmbp2 mouse models of SMARD1, including a null allele, a deletion of C495 (C495del) and a deletion of L362 (L362del). Phenotypic characterization of the IGHMBP2L362del homozygous mutants and IGHMBP2C495del homozygous mutants respectively show a more severe disease presentation than the previous nmd2J model. The IGHMBP2L362del mutants lack a clear denervation in the diaphragm while the IGHMBP2C495del mutants display a neurogenic diaphragmatic phenotype as observed in SMARD1 patients. Characterization of the Ighmbp2-null model indicated neo-natal lethality (median lifespan = 0.5 days). These novel strains expand the spectrum of SMARD1 models to better reflect the clinical continuum observed in the human patients with various IGHMBP2 recessive mutations.

The effects of sodium-glucose cotransporter 2 inhibitors on the 'forgotten' right ventricle

With the progress in diagnosis, treatment and imaging techniques, there is a growing recognition that impaired right ventricular (RV) function profoundly affects the prognosis of patients with heart failure (HF), irrespective of their left ventricular ejection fraction (LVEF). In addition, right HF (RHF) is a common complication associated with various diseases, including congenital heart disease, myocardial infarction (MI), pulmonary arterial hypertension (PAH) and dilated cardiomyopathy (DCM), and it can manifest at any time after left ventricular assist devices (LVADs). The sodium-glucose cotransporter 2 (SGLT2) inhibition by gliflozins has emerged as a cornerstone medicine for managing type 2 diabetes mellitus (T2DM) and HF, with an increasing focus on its potential to enhance RV function. In this review, we aim to present an updated perspective on the pleiotropic effects of gliflozins on the right ventricle and offer insights into the underlying mechanisms. We can ascertain their advantageous impact on the right ventricle by discussing the evidence obtained in animal models and monumental clinical trials. In light of the pathophysiological changes in RHF, we attempt to elucidate crucial mechanisms regarding their beneficial effects, including alleviation of RV overload, reduction of hyperinsulinaemia and inflammatory responses, regulation of nutrient signalling pathways and cellular energy metabolism, inhibition of oxidative stress and myocardial fibrosis, and maintenance of ion balance. Finally, this drug class's potential application and benefits in various clinical settings are described, along with a prospective outlook on future clinical practice and research directions.

Viral fingerprints of the ion channel evolution: compromise of complexity and function

Evolution from precellular supramolecular assemblies to cellular world originated from the ability to make a barrier between the interior of the cell and the outer environment. This step resulted from the possibility to form a membrane, which preserves the cell like a wall of the castle. However, every castle needs gates for trading, i.e. in the case of cell, for controlled exchange of substances. These 'gates' should have the mechanism of opening and closing, guards, entry rules, and so on. Different structures are known to be able to make membrane permeable to various substances, from ions to macromolecules. They are amphipathic peptides, their assemblies, sophisticated membrane channels with numerous transmembrane domains, etc. Upon evolving, cellular world preserved and selected many variants, which, finally, have provided both prokaryotes and eukaryotes with highly selective and regulated ion channels. However, various simpler variants of ion channels are found in viruses. Despite the origin of viruses is still under debates, they have evolved parallelly with the cellular forms of life. Being initial form of the enveloped organisms, reduction of protocells or their escaped parts, viruses might be fingerprints of the evolutionary steps of cellular structures like ion channels. Therefore, viroporins may provide us a necessary information about selection between high functionality and less complex structure in supporting all the requirements for controlled membrane permeability. In this review we tried to elucidate these compromises and show the possible way of the evolution of ion channels, from peptides to complex multi-subunit structures, basing on viral examples.

Canadian College of Medical Geneticists: clinical practice advisory document - responsibility to recontact for reinterpretation of clinical genetic testing

BACKGROUND

Advances in technology and knowledge have facilitated both an increase in the number of patient variants reported and variants reclassified. While there is currently no duty to recontact for reclassified genetic variants, there may be a responsibility. The purpose of this clinical practice advisory document is to provide healthcare practitioners guidance for recontact of previously identified and classified variants, suggest methods for recontact, and principles to consider, taking account patient safety, feasibility, ethical considerations, health service capacity and resource constraints. The target audience are practitioners who order genetic testing, follow patients who have undergone genetic testing and those analysing and reporting genetic testing.

METHODS

A multidisciplinary group of laboratory and ordering clinicians, patient representatives, ethics and legal researchers and a genetic counsellor from the Canadian Association of Genetic Counsellors reviewed the existing literature and guidelines on responsibility to recontact in a clinical context to make recommendations. Comments were collected from the Canadian College of Medical Geneticists (CCMG) Education, Ethics, and Public Policy, Clinical Practice and Laboratory Practice committees, and the membership at large.

RESULTS

Following incorporation of feedback, and external review by the Canadian Association of Genetic Counsellors and patient groups, the document was approved by the CCMG Board of Directors. The CCMG is the Canadian organisation responsible for certifying laboratory and medical geneticists who provide medical genetics services, and for establishing professional and ethical standards for clinical genetics services in Canada.

CONCLUSION

The document describes the ethical and practical factors and suggests a shared responsibility between patients, ordering clinician and laboratory practitioners.

Nonmodifiable Risk Factors Predict Outcomes in Brugada Syndrome

BACKGROUND

Risk stratification in Brugada syndrome (BrS) is based on the occurrence of dynamic factors, such as unexplained syncope and documentation of spontaneous type 1 pattern. At odds with other channelopathies, the role of nonmodifiable risk factors such as sex or genetics remains uncertain.

OBJECTIVES

This study aims to identify nonmodifiable risk factors for the occurrence of life-threatening arrhythmic events (LAEs) and define their clinical utility.

METHODS

Clinical and genetic data from consecutive, unrelated Italian patients with Brugada syndrome screened on the sodium voltage-gated channel alpha subunit 5 (SCN5A) gene and 3 pivotal single-nucleotide variations (formerly single-nucleotide polymorphisms) associated with BrS (rs11708996, rs10428132, and rs9388451) were analyzed using multivariable Cox proportional hazards model.

RESULTS

In 2,182 unrelated patients with BrS (81% males; median age at diagnosis: 41.6 years [Q1-Q3: 33.4-50.3 years]), male sex (HR: 3.6; 95% CI: 1.9-6.9; P = 0.0001), missense SCN5A mutations in BrS-enriched domains (HR: 2.3; 95% CI: 1.2-4.3; P = 0.008), nonmissense SCN5A mutations (HR: 3.2; 95% CI: 1.8-5.7; P < 0.001), and polygenic risk score for BrS (HR: 1.3; 95% CI: 1.0-1.6; P = 0.041) were all independently associated with a significantly higher risk of a first LAE since birth. Based on these results, we derived the nonmodifiable risk of each patient with BrS, and the division of nonmodifiable risk into tertiles identified 3 distinct risk profiles. In an analysis at follow-up, nonmodifiable risk was independently associated with LAE at follow-up (HR: 1.8; 95% CI: 1.1-2.7; P = 0.014), alongside classical predictors including: history of LAE before diagnosis (HR: 13.8; 95% CI: 8.1-23.7; P < 0.0001), history of unexplained syncope before diagnosis (HR: 4.1; 95% CI: 2.4-6.8; P < 0.0001), and spontaneous type 1 pattern at diagnosis (HR: 2.1; 95% CI: 1.2-3.8; P = 0.010). The model was internally validated, and we derived the equation permitting to calculate the granular 5-year risk of experiencing an LAE at follow-up for each patient with BrS, which may be used to facilitate clinical decision-making.

CONCLUSIONS

Our data show that male sex, type of SCN5A mutation, and polygenic risk score for BrS define the nonmodifiable risk of each patient with BrS. Nonmodifiable risk is independently associated with LAE, regardless of symptoms or pattern type.

Generation of an induced pluripotent stem cell line from a Brugada syndrome patient carrying SCN5A/c.3118G>C mutation

Brugada syndrome (BrS) is a hereditary arrhythmia syndrome characterized by right bundle branch block on an electrocardiogram and persistent ST-segment elevation in the right precordial leads. In this study, we describe the establishment of an induced pluripotent stem cell (iPSC) line derived from a BrS patient carrying the novel heterogeneous missense mutation (c.3118G>C; p.G1040R) in the sodium channel protein type 5 subunit alpha (SCN5A) gene. Skin fibroblasts underwent reprogramming using a non-integrated Sendai viral method. Generated iPSC line exhibited embryonic stem cell-like morphology, maintained a normal karyotype, expressed pluripotency markers, and demonstrated the capacity to differentiate into three germ layers.

Do germline genetic variants influence surgical outcomes in drug-resistant epilepsy?

OBJECTIVE

We retrospectively explored patients with drug-resistant epilepsy (DRE) who previously underwent presurgical evaluation to identify correlations between surgical outcomes and pathogenic variants in epilepsy genes.

METHODS

Through an international collaboration, we evaluated adult DRE patients who were screened for surgical candidacy. Patients with pathogenic (P) or likely pathogenic (LP) germline variants in genes relevant to their epilepsy were included, regardless of whether the genetic diagnosis was made before or after the presurgical evaluation. Patients were divided into two groups: resective surgery (RS) and non-resective surgery candidates (NRSC), with the latter group further divided into: palliative surgery (vagus nerve stimulation, deep brain stimulation, responsive neurostimulation or corpus callosotomy) and no surgery. We compared surgical candidacy evaluations and postsurgical outcomes in patients with different genetic abnormalities.

RESULTS

We identified 142 patients with P/LP variants. After presurgical evaluation, 36 patients underwent RS, while 106 patients were NRSC. Patients with variants in ion channel and synaptic transmission genes were more common in the NRSC group (48 %), compared with the RS group (14 %) (p<0.001). Most patients in the RS group had tuberous sclerosis complex. Almost half (17/36, 47 %) in the RS group had Engel class I or II outcomes. Patients with channelopathies were less likely to undergo a surgical procedure than patients with mTORopathies, but when deemed suitable for resection had better surgical outcomes (71 % versus 41 % with Engel I/II). Within the NRSC group, 40 underwent palliative surgery, with 26/40 (65 %) having ≥50 % seizure reduction after mean follow-up of 11 years. Favourable palliative surgery outcomes were observed across a diverse range of genetic epilepsies.

SIGNIFICANCE

Genomic findings, including a channelopathy diagnosis, should not preclude presurgical evaluation or epilepsy surgery, and appropriately selected cases may have good surgical outcomes. Prospective registries of patients with monogenic epilepsies who undergo epilepsy surgery can provide additional insights on outcomes.

Clinical presentation and genetic characterization of early-onset atrial fibrillation in patients affected by long QT syndrome: A single-center experience

INTRODUCTION

Early-onset atrial fibrillation (AF) has already been observed in approximately 2% of patients with genetically proven long QT syndrome (LQTS). This frequency is higher than population-based estimates of early-onset AF. However, the concomitant expression of AF in LQTS is likely underestimated. The purpose of this study was to examine the clinical presentation, genetic background, and outcomes of a cohort of patients with LQTS and early-onset AF referred to a single tertiary center.

METHODS

Twenty-seven patients diagnosed with congenital LQTS were included in the study based on the documentation of early-onset (age ≤50 years) clinical or subclinical AF episodes in all available medical records, including standard electrocardiograms, wearable monitor or cardiac implantable electronic devices.

RESULTS

Seventeen patients experienced clinical AF during the follow-up period. Subclinical AF was detected in 10 patients through insertable or wearable cardiac monitors. In our series, the mean heart rate during AF episodes was found to be relatively low despite the patients' young age and the low or minimal effective doses of beta-blockers used for QTc interval control. All patients exhibiting LQTS and early-onset AF were genotype positive, carrying mutations in the KCNQ1 (66%), KCNH2, KCNE1, and SCN5A genes. Notably, most of these patients carried the same p.(R231C) mutation in the KCNQ1 gene (59%) and were from the same families, suggesting concurrent expression of familial AF and LQTS.

CONCLUSION

LQTS patients are prone to developing clinical and subclinical AF, even at a younger age. The occurrence of early-onset AF in the LQTS population could be more frequent than previously assumed. AF should be considered as a potential dysrhythmia related to LQTS. Our study emphasizes the importance of carefully researching clinical and/or subclinical episodes of AF through strict heart rhythm monitoring in the LQTS population.

Sudden death in epilepsy: the overlap between cardiac and neurological factors

People with epilepsy are at risk of premature death, of which sudden unexpected death in epilepsy (SUDEP), sudden cardiac death (SCD) and sudden arrhythmic death syndrome (SADS) are the primary, partly overlapping, clinical scenarios. We discuss the epidemiologies, risk factors and pathophysiological mechanisms for these sudden death events. We reviewed the existing evidence on sudden death in epilepsy. Classification of sudden death depends on the presence of autopsy and expertise of the clinician determining aetiology. The definitions of SUDEP, SCD and SADS lead to substantial openings for overlap. Seizure-induced arrhythmias constitute a minority of SUDEP cases. Comorbid cardiovascular conditions are the primary determinants of increased SCD risk in chronic epilepsy. Genetic mutations overlap between the states, yet whether these are causative, associated or incidentally present is often unclear. Risk stratification for sudden death in people with epilepsy requires a multidisciplinary approach, including a review of clinical history, toxicological analysis and complete autopsy with histologic and, preferably, genetic examination. We recommend pursuing genetic testing of relatives of people with epilepsy who died suddenly, mainly if a post-mortem genetic test contained a Class IV/V (pathogenic/likely pathogenic) gene variant. Further research may allow more precise differentiation of SUDEP, SCD and SADS and the development of algorithms for risk stratification and preventative strategies.

[Maintenance of chest compressions skill in cardiopulmonary resuscitation in primary health care professionals: Quasi-experimental study]

OBJECTIVE

To validate the efficacy of brief CPR training with dual feedback to maintain the ability to perform quality chest compressions.

MATERIALS AND METHODS

Quasi-experimental study with two groups to evaluate a brief theoretical training followed by a practice with manikin with feedback; Participants: 155 health and non-health professionals from 5 primary care health centers of urban area (43 losses); Main measurements: Characteristics of compressions that were measured before and after the brief training and their maintenance at 3 and 6 months according to the study group. The effect of training and maintenance of skills were analyzed using multiple linear regression models.

RESULTS

155 participants were included, mean age 39.7 years (SD=12.0) with 82.7% female. The training effect had an improvement in mean compression depth (pre-post difference: 3.5, P<.001), total compressions with adequate depth (pre-post difference: 0.2, P<.001) and Total Compressions with Adequate Rhythm (pre-post difference: 0.4, P<.001). The second phase was completed by 112 participants (72.2%). Compression skills declined at 3 months and were lower at 6 months, although the loss of skills was not statistically significant between the two groups.

CONCLUSIONS

An individualized, brief training action with feedback immediately improves the quality of compressions. The progressive loss of skills from 3 to 6 months is not relevant.

Dynamic protein-protein interactions of KCNQ1 and KCNE1 measured by EPR line shape analysis

KCNQ1, also known as Kv7.1, is a voltage gated potassium channel that associates with the KCNE protein family. Mutations in this protein has been found to cause a variety of diseases including Long QT syndrome, a type of cardiac arrhythmia where the QT interval observed on an electrocardiogram is longer than normal. This condition is often aggravated during strenuous exercise and can cause fainting spells or sudden death. KCNE1 is an ancillary protein that interacts with KCNQ1 in the membrane at varying molar ratios. This interaction allows for the flow of potassium ions to be modulated to facilitate repolarization of the heart. The interaction between these two proteins has been studied previously with cysteine crosslinking and electrophysiology. In this study, electron paramagnetic resonance (EPR) spectroscopy line shape analysis in tandem with site directed spin labeling (SDSL) was used to observe changes in side chain dynamics as KCNE1 interacts with KCNQ1. KCNE1 was labeled at different sites that were found to interact with KCNQ1 based on previous literature, along with sites outside of that range as a control. Once labeled KCNE1 was incorporated into vesicles, KCNQ1 (helices S1-S6) was titrated into the vesicles. The line shape differences observed upon addition of KCNQ1 are indicative of an interaction between the two proteins. This method provides a first look at the interactions between KCNE1 and KCNQ1 from a dynamics perspective using the full transmembrane portion of KCNQ1.

Novel heterozygous mutation of CACNA2D1 gene in a Chinese family with arrhythmia

BACKGROUND

Primary electrical disorders (PEDs) are a group of cardiac rhythm abnormalities that occur in the absence of detectable structural heart disease and are a significant cause of sudden cardiac death (SCD). The initiation of cardiac muscle contraction and relaxation is orchestrated by the action potential (AP), generated through ionic changes across the membrane. Mutations in the AP-related gene CACNA2D1 have been identified as a causative factor for PED.

METHODS

We recruited a Chinese family with a history of arrhythmia. The proband has experienced palpitations and chest tightness for over 40 years, with symptoms worsening over the past year. Whole exome sequencing (WES) was used to determine the genetic etiologies in this family.

RESULTS

A novel heterozygous missense mutation (NM_000722.3: c.1685G > C;p.G562A) of CACNA2D1 gene was detected. Genotyping of the proband's parents indicated that the arrhythmia phenotype in the proband was caused by a de novo mutation.

CONCLUSIONS

WES was utilized to explore the genetic etiology in a family with arrhythmia, leading to the identification of a novel mutation in the CACNA2D1 gene. This study not only expands the mutation spectrum of the CACNA2D1 gene but also contributes to genetic counseling and clinical diagnosis for this family.

2024 HRS expert consensus statement on arrhythmias in the athlete: Evaluation, treatment, and return to play

Youth and adult participation in sports continues to increase, and athletes may be diagnosed with potentially arrhythmogenic cardiac conditions. This international multidisciplinary document is intended to guide electrophysiologists, sports cardiologists, and associated health care team members in the diagnosis, treatment, and management of arrhythmic conditions in the athlete with the goal of facilitating return to sport and avoiding the harm caused by restriction. Expert, disease-specific risk assessment in the context of athlete symptoms and diagnoses is emphasized throughout the document. After appropriate risk assessment, management of arrhythmias geared toward return to play when possible is addressed. Other topics include shared decision-making and emergency action planning. The goal of this document is to provide evidence-based recommendations impacting all areas in the care of athletes with arrhythmic conditions. Areas in need of further study are also discussed.

Diverse Concepts in Definitions of Dilated Cardiomyopathy: Theory and Practice

Our understanding of dilated cardiomyopathy (DCM) is evolving as new insights into the underlying pathophysiology become available. Professional organizations and clinical experts are improving definitions of DCM, allowing for more accurate treatment recommendations. This review summarized key published literature describing definitions and/or diagnostic criteria for DCM. Embase was searched from database inception to September 19, 2022 for 1) publications reporting definitions of DCM by major professional organizations and related opinion papers, and 2) clinical studies in DCM and heart failure with reduced ejection fraction. Sixty-eight records were included in this review. Definitions of DCM provided by two major professional organizations (American Heart Association (AHA) and European Society of Cardiology (ESC)) agreed on the clinical presentation of DCM; however, they differed in the classification of DCM within the larger context of cardiomyopathy taxonomies. Both organizations agreed that DCM could be clinically defined by the presence of left ventricular dilation and contractile dysfunction in the absence of abnormal loading conditions and severe coronary artery disease. AHA guidelines divided cardiomyopathies into two major groups (primary and secondary) based on predominant organ involvement. DCM was classified as primary cardiomyopathy with mixed (genetic and/or acquired) etiology. Conversely, ESC published a clinically oriented taxonomy in which cardiomyopathies were grouped into specific morphological and functional phenotypes; each was subclassified into familial or non-familial forms. Opinion papers further elaborated on the complex interplay between genetics and environment in the etiology of DCM. Several articles summarized the importance of the new and updated diagnostic tools, such as cardiac magnetic resonance imaging, electrocardiogram, and other biomarkers, in correctly identifying the etiology of DCM. Within clinical studies, most inclusion criteria used standard definitions proposed by leading professional associations (AHA and ESC). Clinical study investigators sometimes used a narrower definition of DCM using additional criteria for the left ventricular ejection fraction threshold value and left ventricular dilatation. Current efforts in cardiology research are focused on a more granular understanding of DCM etiology and the natural history of the disease. Definitions of DCM found in clinical studies mainly rely on published guidelines, with some studies adding idiosyncratic inclusion criteria refining the broad definitions of DCM.

Rare Genetic Variants in Young Adults Requiring Pacemaker Implantation

BACKGROUND

Genetic disease has recently emerged as a cause of cardiac conduction disorders (CCDs), but the diagnostic yield of genetic testing and the contribution of the different genes to CCD is still unsettled.

OBJECTIVES

This study sought to determine the diagnostic yield of genetic testing in young adults with CCD of unknown etiology requiring pacemaker implantation. We also studied the prevalence of rare protein-altering variants across individual genes and functional gene groups.

METHODS

We performed whole exome sequencing in 150 patients with CCD of unknown etiology who had permanent pacemaker implanted at age ≤60 years at 14 Spanish hospitals. Prevalence of rare protein-altering variants in patients with CCD was compared with a reference population of 115,522 individuals from gnomAD database (control subjects).

RESULTS

Among 39 prioritized genes, patients with CCD had more rare protein-altering variants than control subjects (OR: 2.39; 95% CI: 1.75-3.33). Significant enrichment of rare variants in patients with CCD was observed in all functional gene groups except in the desmosomal genes group. Rare variants in the nuclear envelope genes group exhibited the strongest association with CCD (OR: 6.77; 95% CI: 3.71-13.87). Of note, rare variants in sarcomeric genes were also enriched (OR: 1.73; 95% CI: 1.05-3.10). An actionable genetic variant was detected in 21 patients (14%), with LMNA being the most frequently involved gene (4.6%).

CONCLUSIONS

Unrecognized rare genetic variants increase the risk of CCD in young adults with CCD of unknown etiology. Genetic testing should be performed in patients age ≤60 years with CCD of unknown etiology. The role of genetic variants in sarcomeric genes as a cause of CCD should be further investigated.

The Genetic Factors Influencing Cardiomyopathies and Heart Failure across the Allele Frequency Spectrum

Heart failure (HF) remains a major cause of mortality and morbidity worldwide. Understanding the genetic basis of HF allows for the development of disease-modifying therapies, more appropriate risk stratification, and personalised management of patients. The advent of next-generation sequencing has enabled genome-wide association studies; moving beyond rare variants identified in a Mendelian fashion and detecting common DNA variants associated with disease. We summarise the latest GWAS and rare variant data on mixed and refined HF aetiologies, and cardiomyopathies. We describe the recent understanding of the functional impact of titin variants and highlight FHOD3 as a novel cardiomyopathy-associated gene. We describe future directions of research in this field and how genetic data can be leveraged to improve the care of patients with HF.

Phenotype-genotype spectrum of a cohort of congenital muscular dystrophies: a single-centre experience from India

Congenital Muscular Dystrophies (CMD) are phenotypically and genotypically heterogenous disorders with a prevalence of 0.68 to 2.5/100,000, contributing to significant morbidity and mortality. We aimed to study the phenotype-genotype spectrum of genetically confirmed cases of CMD. This was retrospective & descriptive study done at a quaternary care referral centre in south India. Genetically confirmed cases of CMDs seen between 2010 to 2020 were recruited. Detailed clinical history, including pedigree, MRI brain/muscle, next generation sequencing results of 61 CMD cases were collected. Collagen VI-related dystrophy (COL6-RD) (36%) was the most common subtype with variants frequently seen in COL6A1 gene. Other CMDs identified were LAMA2-RD (26%), alpha-dystroglycan-RD (19%), LMNA-RD (8%), CHKB-RD (7%) and SEPN1-RD (3%). Similar to previous cohorts, overall, missense variants were common in COL-6 RD. Variants in triple helical domain (THD) of COL6-RD were seen in 11/22 patients, 5 of whom were ambulatory contrary to previous literature citing severe disease with these variants. However, our follow-up period was shorter. In the LAMA2-RD, 2/16 patients were ambulatory & all 16 carried truncating variants. Among dystroglycanopathies, FKRP-RD was the commonest. Milder phenotype of FKRP- RD was observed with variant c.1343C > T, which was also a recurrent variant in our cohort. p.Arg249Trp variant in LMNA-CMD associated with early loss of ambulation was also identified in 1/5 of our patients who expired at age 2.8 years. The current retrospective series provides detailed clinical features and mutation patterns of genetically confirmed cases of CMD from a single center in India.