Congenital long QT syndrome

Population-specific variations in KCNH2 predispose patients to delayed ventricular repolarization upon dihydroartemisinin-piperaquine therapy

Dihydroartemisinin-piperaquine is efficacious for the treatment of uncomplicated malaria and its use is increasing globally. Despite the positive results in fighting malaria, inhibition of the Kv11.1 channel (hERG; encoded by the KCNH2 gene) by piperaquine has raised concerns about cardiac safety. Whether genetic factors could modulate the risk of piperaquine-mediated QT prolongations remained unclear. Here, we first profiled the genetic landscape of KCNH2 variability using data from 141,614 individuals. Overall, we found 1,007 exonic variants distributed over the entire gene body, 555 of which were missense. By optimizing the gene-specific parametrization of 16 partly orthogonal computational algorithms, we developed a KCNH2-specific ensemble classifier that identified a total of 116 putatively deleterious missense variations. To evaluate the clinical relevance of KCNH2 variability, we then sequenced 293 Malian patients with uncomplicated malaria and identified 13 variations within the voltage sensing and pore domains of Kv11.1 that directly interact with channel blockers. Cross-referencing of genetic and electrocardiographic data before and after piperaquine exposure revealed that carriers of two common variants, rs1805121 and rs41314375, experienced significantly higher QT prolongations (ΔQTc of 41.8 ms and 61 ms, respectively, vs 14.4 ms in controls) with more than 50% of carriers having increases in QTc >30 ms. Furthermore, we identified three carriers of rare population-specific variations who experienced clinically relevant delayed ventricular repolarization. Combined, our results map population-scale genetic variability of KCNH2 and identify genetic biomarkers for piperaquine-induced QT prolongation that could help to flag at-risk patients and optimize efficacy and adherence to antimalarial therapy.

Advances in the study of protein folding and endoplasmic reticulum-associated degradation in mammal cells

The endoplasmic reticulum is a key site for protein production and quality control. More than one-third of proteins are synthesized and folded into the correct three-dimensional conformation in the endoplasmic reticulum. However, during protein folding, unfolded and/or misfolded proteins are prone to occur, which may lead to endoplasmic reticulum stress. Organisms can monitor the quality of the proteins produced by endoplasmic reticulum quality control (ERQC) and endoplasmic reticulum-associated degradation (ERAD), which maintain endoplasmic reticulum protein homeostasis by degrading abnormally folded proteins. The underlying mechanisms of protein folding and ERAD in mammals have not yet been fully explored. Therefore, this paper reviews the process and function of protein folding and ERAD in mammalian cells, in order to help clinicians better understand the mechanism of ERAD and to provide a scientific reference for the treatment of diseases caused by abnormal ERAD.

In Vivo Base Editing of Scn5a Rescues Type 3 Long QT Syndrome in Mice

BACKGROUND

Pathogenic variants in SCN5A can result in long QT syndrome type 3, a life-threatening genetic disease. Adenine base editors can convert targeted A T base pairs to G C base pairs, offering a promising tool to correct pathogenic variants.

METHODS

We generated a long QT syndrome type 3 mouse model by introducing the T1307M pathogenic variant into the Scn5a gene. The adenine base editor was split into 2 smaller parts and delivered into the heart by adeno-associated virus serotype 9 (AAV9-ABEmax) to correct the T1307M pathogenic variant.

RESULTS

Both homozygous and heterozygous T1307M mice showed significant QT prolongation. Carbachol administration induced Torsades de Pointes or ventricular tachycardia for homozygous T1307M mice (20%) but not for heterozygous or wild-type mice. A single intraperitoneal injection of AAV9-ABEmax at postnatal day 14 resulted in up to 99.20% Scn5a transcripts corrected in T1307M mice. Scn5a mRNA correction rate >60% eliminated QT prolongation; Scn5a mRNA correction rate <60% alleviated QT prolongation. Partial Scn5a correction resulted in cardiomyocytes heterogeneity, which did not induce severe arrhythmias. We did not detect off-target DNA or RNA editing events in ABEmax-treated mouse hearts.

CONCLUSIONS

These findings show that in vivo AAV9-ABEmax editing can correct the variant Scn5a allele, effectively ameliorating arrhythmia phenotypes. Our results offer a proof of concept for the treatment of hereditary arrhythmias.

Targeted activation of human ether-à-go-go-related gene channels rescues electrical instability induced by the R56Q+/- long QT syndrome variant

AIMS

Long QT syndrome type 2 (LQTS2) is associated with inherited variants in the cardiac human ether-à-go-go-related gene (hERG) K+ channel. However, the pathogenicity of hERG channel gene variants is often uncertain. Using CRISPR-Cas9 gene-edited hiPSC-derived cardiomyocytes (hiPSC-CMs), we investigated the pathogenic mechanism underlying the LQTS-associated hERG R56Q variant and its phenotypic rescue by using the Type 1 hERG activator, RPR260243.

METHODS AND RESULTS

The above approaches enable characterization of the unclear causative mechanism of arrhythmia in the R56Q variant (an N-terminal PAS domain mutation that primarily accelerates channel deactivation) and translational investigation of the potential for targeted pharmacologic manipulation of hERG deactivation. Using perforated patch clamp electrophysiology of single hiPSC-CMs, programmed electrical stimulation showed that the hERG R56Q variant does not significantly alter the mean action potential duration (APD90). However, the R56Q variant increases the beat-to-beat variability in APD90 during pacing at constant cycle lengths, enhances the variance of APD90 during rate transitions, and increases the incidence of 2:1 block. During paired S1-S2 stimulations measuring electrical restitution properties, the R56Q variant was also found to increase the variability in rise time and duration of the response to premature stimulations. Application of the hERG channel activator, RPR260243, reduces the APD variance in hERG R56Q hiPSC-CMs, reduces the variability in responses to premature stimulations, and increases the post-repolarization refractoriness.

CONCLUSION

Based on our findings, we propose that the hERG R56Q variant leads to heterogeneous APD dynamics, which could result in spatial dispersion of repolarization and increased risk for re-entry without significantly affecting the average APD90. Furthermore, our data highlight the antiarrhythmic potential of targeted slowing of hERG deactivation gating, which we demonstrate increases protection against premature action potentials and reduces electrical heterogeneity in hiPSC-CMs.

Long QT syndrome-associated calmodulin variants disrupt the activity of the slowly activating delayed rectifier potassium channel

Calmodulin (CaM) is a highly conserved mediator of calcium (Ca2+ )-dependent signalling and modulates various cardiac ion channels. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS). LQTS patients display prolonged ventricular recovery times (QT interval), increasing their risk of incurring life-threatening arrhythmic events. Loss-of-function mutations to Kv7.1 (which drives the slow delayed rectifier potassium current, IKs, a key ventricular repolarising current) are the largest contributor to congenital LQTS (>50% of cases). CaM modulates Kv7.1 to produce a Ca2+ -sensitive IKs, but little is known about the consequences of LQTS-associated CaM mutations on Kv7.1 function. Here, we present novel data characterising the biophysical and modulatory properties of three LQTS-associated CaM variants (D95V, N97I and D131H). We showed that mutations induced structural alterations in CaM and reduced affinity for Kv7.1, when compared with wild-type (WT). Using HEK293T cells expressing Kv7.1 channel subunits (KCNQ1/KCNE1) and patch-clamp electrophysiology, we demonstrated that LQTS-associated CaM variants reduced current density at systolic Ca2+ concentrations (1 μm), revealing a direct QT-prolonging modulatory effect. Our data highlight for the first time that LQTS-associated perturbations to CaM's structure impede complex formation with Kv7.1 and subsequently result in reduced IKs. This provides a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype. KEY POINTS: Calmodulin (CaM) is a ubiquitous, highly conserved calcium (Ca2+ ) sensor playing a key role in cardiac muscle contraction. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS), a life-threatening cardiac arrhythmia syndrome. LQTS-associated CaM variants (D95V, N97I and D131H) induced structural alterations, altered binding to Kv7.1 and reduced IKs. Our data provide a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype.

Prediction of Kv11.1 potassium channel PAS-domain variants trafficking via machine learning

Congenital long QT syndrome (LQTS) is characterized by a prolonged QT-interval on an electrocardiogram (ECG). An abnormal prolongation in the QT-interval increases the risk for fatal arrhythmias. Genetic variants in several different cardiac ion channel genes, including KCNH2, are known to cause LQTS. Here, we evaluated whether structure-based molecular dynamics (MD) simulations and machine learning (ML) could improve the identification of missense variants in LQTS-linked genes. To do this, we investigated KCNH2 missense variants in the Kv11.1 channel protein shown to have wild type (WT) like or class II (trafficking-deficient) phenotypes in vitro. We focused on KCNH2 missense variants that disrupt normal Kv11.1 channel protein trafficking, as it is the most common phenotype for LQTS-associated variants. Specifically, we used computational techniques to correlate structural and dynamic changes in the Kv11.1 channel protein PAS domain (PASD) with Kv11.1 channel protein trafficking phenotypes. These simulations unveiled several molecular features, including the numbers of hydrating waters and hydrogen bonding pairs, as well as folding free energy scores, that are predictive of trafficking. We then used statistical and machine learning (ML) (Decision tree (DT), Random forest (RF), and Support vector machine (SVM)) techniques to classify variants using these simulation-derived features. Together with bioinformatics data, such as sequence conservation and folding energies, we were able to predict with reasonable accuracy (≈75%) which KCNH2 variants do not traffic normally. We conclude that structure-based simulations of KCNH2 variants localized to the Kv11.1 channel PASD led to an improvement in classification accuracy. Therefore, this approach should be considered to complement the classification of variant of unknown significance (VUS) in the Kv11.1 channel PASD.

Application of next generation sequencing in cardiology: current and future precision medicine implications

Inherited cardiovascular diseases are highly heterogeneous conditions with multiple genetic loci involved. The application of advanced molecular tools, such as Next Generation Sequencing, has facilitated the genetic analysis of these disorders. Accurate analysis and variant identification are required to maximize the quality of the sequencing data. Therefore, the application of NGS for clinical purposes should be limited to laboratories with a high level of technological expertise and resources. In addition, appropriate gene selection and variant interpretation can result in the highest possible diagnostic yield. Implementation of genetics in cardiology is imperative for the accurate diagnosis, prognosis and management of several inherited disorders and could eventually lead to the realization of precision medicine in this field. However, genetic testing should also be accompanied by an appropriate genetic counseling procedure that clarifies the significance of the genetic analysis results for the proband and his family. In this regard, a multidisciplinary collaboration among physicians, geneticists, and bioinformaticians is imperative. In the present review, we address the current state of knowledge regarding genetic analysis strategies employed in the field of cardiogenetics. Variant interpretation and reporting guidelines are explored. Additionally, gene selection procedures are accessed, with a particular emphasis on information concerning gene-disease associations collected from international alliances such as the Gene Curation Coalition (GenCC). In this context, a novel approach to gene categorization is proposed. Moreover, a sub-analysis is conducted on the 1,502,769 variation records with submitted interpretations in the Clinical Variation (ClinVar) database, focusing on cardiology-related genes. Finally, the most recent information on genetic analysis's clinical utility is reviewed.

Endocannabinoids enhance hKV7.1/KCNE1 channel function and shorten the cardiac action potential and QT interval

BACKGROUND

Genotype-positive patients who suffer from the cardiac channelopathy Long QT Syndrome (LQTS) may display a spectrum of clinical phenotypes, with often unknown causes. Therefore, there is a need to identify factors influencing disease severity to move towards an individualized clinical management of LQTS. One possible factor influencing the disease phenotype is the endocannabinoid system, which has emerged as a modulator of cardiovascular function. In this study, we aim to elucidate whether endocannabinoids target the cardiac voltage-gated potassium channel K_V7.1/KCNE1, which is the most frequently mutated ion channel in LQTS.

METHODS

We used two-electrode voltage clamp, molecular dynamics simulations and the E4031 drug-induced LQT2 model of ex-vivo guinea pig hearts.

FINDINGS

We found a set of endocannabinoids that facilitate channel activation, seen as a shifted voltage-dependence of channel opening and increased overall current amplitude and conductance. We propose that negatively charged endocannabinoids interact with known lipid binding sites at positively charged amino acids on the channel, providing structural insights into why only specific endocannabinoids modulate K_V7.1/KCNE1. Using the endocannabinoid ARA-S as a prototype, we show that the effect is not dependent on the KCNE1 subunit or the phosphorylation state of the channel. In guinea pig hearts, ARA-S was found to reverse the E4031-prolonged action potential duration and QT interval.

INTERPRETATION

We consider the endocannabinoids as an interesting class of hK_V7.1/KCNE1 channel modulators with putative protective effects in LQTS contexts.

FUNDING

ERC (No. 850622), Canadian Institutes of Health Research, Canada Research Chairs and Compute Canada, Swedish National Infrastructure for Computing.

Cardiac arrest associated with non-toxigenic corynebacterium diphtheria strain: A case report

Here we document a rare, acute, infection caused by non-toxigenic Corynebacterium diphtheriae and the resulting unique and severe clinical sequelae. Our patient was a young man with no known pre-existing conditions that presented in cardiopulmonary arrest. We contrast this case with prior instances of non-toxigenic C. diphtheriae strain infection in the United States and summarize the literature that suggests systemic infection can result in cardiogenic toxicity. We speculate on a possible missed, pre-existing condition that could have increased this patient's susceptibility to poor clinical outcome.

Cardiac Alternans: From Bedside to Bench and Back

Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.

A Bio-Social Model during the First 1000 Days Optimizes Healthcare for Children with Developmental Disabilities

Most children with developmental disabilities (DD) live in resource-limited countries (LMIC) or high-income country medical deserts (HICMD). A social contract between healthcare providers and families advocates for accurate diagnoses and effective interventions to treat diseases and toxic stressors. This bio-social model emphasizes reproductive health of women with trimester-specific maternal and pediatric healthcare interactions. Lifelong neuronal connectivity is more likely established across 80% of brain circuitries during the first 1000 days. Maladaptive gene-environment (G x E) interactions begin before conception later presenting as maternal-placental-fetal (MPF) triad, neonatal, or childhood neurologic disorders. Synergy between obstetrical and pediatric healthcare providers can reduce neurologic morbidities. Partnerships between healthcare providers and families should begin during the first 1000 days to address diseases more effectively to moderate maternal and childhood adverse effects. This bio-social model lowers the incidence and lessens the severity of sequalae such as DD. Access to genetic-metabolomic, neurophysiologic and neuroimaging evaluations enhances clinical decision-making for more effective interventions before full expression of neurologic dysfunction. Diagnostic accuracy facilitates developmental interventions for effective preschool planning. A description of a mother-child pair in a HIC emphasizes the time-sensitive importance for early interventions that influenced brain health throughout childhood. Partnership by her parents with healthcare providers and educators provided effective healthcare and lessened adverse effects. Effective educational interventions were later offered through her high school graduation. Healthcare disparities in LMIC and HICMD require that this bio-social model of care begin before the first 1000 days to effectively treat the most vulnerable women and children. Prioritizing family planning followed by prenatal, neonatal and child healthcare improves wellness and brain health. Familiarity with educational neuroscience for teachers applies neurologic diagnoses for effective individual educational plans. Integrating diversity and inclusion into medical and educational services cross socioeconomic, ethnic, racial, and cultural barriers with life-course benefits. Families require knowledge to recognize risks for their children and motivation to sustain relationships with providers and educators for optimal outcomes. The WHO sustainable development goals promote brain health before conception through the first 1000 days. Improved education, employment, and social engagement for all persons will have intergenerational and transgenerational benefits for communities and nations.

TOXOPLASMOSIS RETINOCHOROIDITIS MASQUERADING AS ENDOGENOUS ENDOPHTHALMITIS IN A CASE OF CONGENITAL LONG QT SYNDROME

PURPOSE

To describe the diagnostic and treatment challenges of a case of presumed acquired macula-involving toxoplasmosis retinochoroiditis.

METHODS

Case report of a woman with congenital long QT syndrome presenting with retinochoroiditis after undergoing a cardiac procedure. Laboratory analysis, ocular fluid biopsy, and multimodal imaging were obtained.

RESULTS

Ophthalmic examination was significant for decreased vision and a macula-involving chorioretinal lesion concerning for endogenous endophthalmitis. Multimodal imaging showed a focal, full-thickness necrotizing process associated with vitritis, retinal edema, and choroidal thickening. Analysis of peripheral blood revealed elevated serum toxoplasma Immunoglobulin G titers. Blood cultures and a transesophageal echocardiogram were negative for endocarditis. Aqueous and vitreous specimens were negative for an infectious polymerase chain reaction panel, including toxoplasmosis and negative bacterial and fungal cultures. A diagnosis of presumed acquired toxoplasmosis retinochoroiditis was made and treated with a combination of oral and intravitreal antiparasitic medications resulting in healing of the retinochoroiditis.

CONCLUSION

To the authors' knowledge, this is the first reported case of acquired toxoplasmosis retinochoroiditis in an immunocompetent patient with congenital long QT syndrome masquerading as endogenous endophthalmitis. The association of congenital long QT syndrome and a recent cardiac procedure with a risk for endogenous endophthalmitis complicated the diagnosis, clinical course, and treatment options. Our case emphasizes the importance of a thorough patient history, comprehensive clinical examination, and supportive multimodal imaging that were used to characterize the infectious process and guide empirical treatment. In addition, laboratory analysis, comanagement with other specialists, and evaluating the response to antitoxoplasma therapy were all instrumental in the eventual diagnosis and treatment of ocular toxoplasmosis in this atypical case.

Cerebral Seizures in an Adolescent with Jervell and Lange-Nielsen Syndrome: It May Not Be Epilepsy

A 13-year-old girl with Jervell and Lange-Nielsen syndrome associated congenital long QT syndrome (LQTS) and central deafness was admitted for generalized seizures. LQTS had been diagnosed after birth and confirmed at genetic testing. β-blocker treatment was immediately started. Despite this, since the age of 12 months, recurrent cerebral seizures occurred leading to the diagnosis of epilepsy. Anti-convulsive therapy was initiated but without success. At the last admission, nadolol dosage seemed infratherapeutic. Considering malignant ventricular arrhythmias as the cause of seizures, the β-blocker dosage was adjusted to weight and levels of magnesium and potassium optimized. Furthermore, the patient received an implantable Medtronic Reveal LINQ Recorder^®. Since then, the adolescent has been asymptomatic with no arrhythmia documented. LQTS is due to one or more mutations of genes coding for ion channels. It may induce malignant ventricular arrhythmias and is a major cause of sudden cardiac death in children. Generalized cerebral seizures are extra-cardiac manifestations caused by decreased cerebral perfusion during ventricular arrhythmia. They are commonly misinterpreted as manifestations of epilepsy. For any patient with known or unknown LQTS who presents seizures with resistance to anti-convulsive therapy, a cardiac electrophysiological investigation should be performed promptly to ensure etiological diagnosis and optimize treatment.

Case Report: Prenatal Whole-Exome Sequencing Identified a Novel Nonsense Mutation of the KCNH2 Gene in a Fetus With Familial 2q14.2 Duplication

Background: Pathogenic mutations in the KCNH2 gene were associated with long QT syndrome 2 (LQT2), which typically manifest in a prolonged QT interval and may lead to recurrent syncopes, seizure, or sudden death. Limited reports indicated that the KCNH2 mutations would result in LQT2 combined with tetralogy of fallot. Our goal was to present an additional case of LQT2 combined with the tetralogy of fallot in a fetus with a novel KCNH2 mutation.

Case presentation: Enrolled in this study was a 23-year-old pregnant woman from Quanzhou Fujian province, China. In her pregnancy, fetal ultrasound anomalies were identified, including tetralogy of fallot, coronary sinus enlargement, and persistent left superior vena cava. No chromosomal abnormality was detected by fetal karyotype analysis. However, 238.1-kb duplication in the 2q14.2 region containing the GLI2 gene was observed in the fetus by chromosomal array analysis, which was inherited from the mother with normal clinical features and interpreted as a variant of uncertain significance (VOUS). Furthermore, whole-exome sequencing (WES) detection identified a novel nonsense c.1907C &gt; G (p.S636*) mutation in the KCNH2 gene in the fetus, and it was classified as a likely pathogenic variant, according to the ACMG guidelines. Parental verification analysis indicated that c.1907C &gt; G (p.S636*) mutation was inherited from the mother.

Conclusion: In this study, we believe that 2q14.2 duplication may not be the reason for fetal heart defects; moreover, we described an additional case with KCNH2 gene mutation, which may lead to LQTS and be associated with congenital heart defects. In addition, our study further confirms the application value of the WES technology in prenatal genetic etiology diagnosis of fetuses with structural anomalies and unexplained structural variants.

Model-based estimation of QT intervals of mouse fetal electrocardiogram

Background

Abnormal prolongation in the QT interval or long QT syndrome (LQTS) is associated with several cardiac complications such as sudden infant death syndrome (SIDS). LQTS is believed to be linked to genetic mutations which can be understood by using animal models, such as mice models. Nevertheless, the research related to fetal QT interval in mice is still limited because of challenges associated with T wave measurements in fetal electrocardiogram (fECG). Reliable measurement of T waves is essential for estimating their end timings for QT interval assessment.

Results

A mathematical model was used to estimate QT intervals. Estimated QT intervals were validated with Q-aortic closure (Q-Ac) intervals of Doppler ultrasound (DUS) and comparison between both showed good agreement with a correlation coefficient higher than 0.88 (r > 0.88, P < 0.05).

Conclusion

Model-based estimation of QT intervals can help in better understanding of QT intervals in fetal mice.

The ERG1 K+ Channel and Its Role in Neuronal Health and Disease

The ERG1 potassium channel, encoded by KCNH2, has long been associated with cardiac electrical excitability. Yet, a growing body of work suggests that ERG1 mediates physiology throughout the human body, including the brain. ERG1 is a regulator of neuronal excitability, ERG1 variants are associated with neuronal diseases (e.g., epilepsy and schizophrenia), and ERG1 serves as a potential therapeutic target for neuronal pathophysiology. This review summarizes the current state-of-the-field regarding the ERG1 channel structure and function, ERG1’s relationship to the mammalian brain and highlights key questions that have yet to be answered.

Congenital long QT syndrome: A challenging diagnosis by fetal echocardiography

The diagnosis of long QT syndrome (LQTS) in utero presents many challenges for clinicians, and there is high risk for intrauterine fetal demise as life-threatening arrhythmias develop secondary to QT prolongation. We describe a challenging case of a fetus presenting with sinus bradycardia and second-degree atrioventricular block with episodes of ventricular tachycardia. A prenatal diagnosis of LQTS was suspected given the fetal echocardiographic findings of a short ventricular relaxation time, due to extremely prolonged refractory period. The patient was delivered emergently due to Torsade's with hydrops, with ongoing arrhythmia despite medical management requiring implantation of pacemaker and sympathectomy. Early recognition of LQTS is important to optimize fetal survival with prompt medical management.

OUP accepted manuscript

Current exercise recommendations make it difficult for long QT syndrome (LQTS) patients to adopt a physically active and/or athletic lifestyle. The purpose of this review is to summarize the current evidence, identify knowledge gaps, and discuss research perspectives in the field of exercise and LQTS. The first aim is to document the influence of exercise training, exercise stress, and postural change interventions on ventricular repolarization in LQTS patients, while the second aim is to describe electrophysiological measurements used to study the above. Studies examining the effects of exercise on congenital or acquired LQTS in human subjects of all ages were included. Systematic searches were performed on 1 October 2021, through PubMed (NLM), Ovid Medline, Ovid All EBM Reviews, Ovid Embase, and ISI Web of Science, and limited to articles written in English or French. A total of 1986 LQTS patients and 2560 controls were included in the 49 studies. Studies were mainly case-control studies (n = 41) and examined exercise stress and/or postural change interventions (n = 48). One study used a 3-month exercise training program. Results suggest that LQTS patients have subtype-specific repolarization responses to sympathetic stress. Measurement methods and quality were found to be very heterogeneous, which makes inter-study comparisons difficult. In the absence of randomized controlled trials, the current recommendations may have long-term risks for LQTS patients who are discouraged from performing physical activity, rendering its associated health benefits out of range. Future research should focus on discovering the most appropriate levels of exercise training that promote ventricular repolarization normalization in LQTS.

American College of Rheumatology White Paper on Antimalarial Cardiac Toxicity

Hydroxychloroquine (HCQ) and chloroquine (CQ) are well-established medications used in treating systemic lupus erythematosus and rheumatoid arthritis, as well as skin conditions such as cutaneous lupus erythematosus. In rare cases, arrhythmias and conduction system abnormalities, as well as cardiomyopathy, have been reported in association with HCQ/CQ use. Recently, however, the corrected QT interval (QTc)-prolonging potential of these medications, and risk of torsade de pointes (TdP) in particular, have been highlighted in the setting of their experimental use for COVID-19 infection. This report was undertaken to summarize the current understanding of HCQ/CQ cardiac toxicity, describe QTc prolongation and TdP risks, and discuss areas of priority for future research. A working group of experts across rheumatology, cardiology, and dermatology performed a nonsystematic literature review and offered a consensus-based expert opinion. Current data clearly indicate that HCQ and CQ are invaluable medications in the management of rheumatic and dermatologic diseases, but they are associated with QTc prolongation by directly affecting cardiac repolarization. Prescribing clinicians should be cognizant of this small effect, especially in patients taking additional medications that prolong the QTc interval. Long-term use of HCQ/CQ may lead to a cardiomyopathy associated with arrhythmias and heart failure. Risk and benefit assessment should be considered prior to initiation of any medication, and both initial and ongoing risk-benefit assessments are important with regard to prescription of HCQ/CQ. While cardiac toxicity related to HCQ/CQ treatment of rheumatic diseases is rarely reported, it can be fatal. Awareness of the potential adverse cardiac effects of HCQ and CQ can increase the safe use of these medications. There is a clear need for additional research to allow better understanding of the cardiovascular risk and safety profile of these therapies used in the management of rheumatic and cutaneous diseases.

Heart rhythm characterization during sudden cardiac death in dogs

INTRODUCTION/OBJECTIVES

Inherited or acquired arrhythmic disorders and cardiac disease have been associated with sudden cardiac death (SCD) in dogs. The electrical mechanism related to death in most of these cases is unknown. This retrospective study aimed to describe arrhythmic events in dogs that experienced SCD during Holter monitoring.

ANIMALS, MATERIALS AND METHODS

Nineteen client-owned dogs that experienced SCD during Holter examination were included. Clinical records from a Holter service database were reviewed, and both the rhythm preceding death and the dominant rhythm causing SCD were analysed. Clinical data, Holter diaries and echocardiographic diagnosis were also evaluated.

RESULTS

Structural heart disease was identified in 12/19 dogs (dilated cardiomyopathy in five dogs, arrhythmogenic right ventricular cardiomyopathy in four dogs, myxomatous mitral valve disease in two dogs, and suspected myocarditis in one dog), five of which had concurrent congestive heart failure. Sudden cardiac death was related to ventricular premature complexes or monomorphic ventricular tachycardia degenerating into ventricular fibrillation in 42% of dogs, polymorphic ventricular tachycardia, or torsade de pointes-like inducing ventricular fibrillation in 21%, and asystole or presumptive agonal pulseless electrical activity triggered by malignant bradyarrhythmias in 37%.

CONCLUSIONS

The most common rhythm associated with SCD in our population of dogs was ventricular tachycardia leading to ventricular fibrillation, although bradyarrhythmia-related SCD, possibly related to inappropriate vagal reflexes, was also a notable cause.

Exercise-Associated Sudden Death in Finnish Standardbred and Coldblooded Trotters - A Case Series With Pedigree Analysis

Exercise-associated sudden deaths (EASDs) are deaths occurring unexpectedly during or immediately after exercise. Sudden cardiac death (SCD) is one cause of EASD. Cardiac arrhythmias caused by genetic variants have been linked to SCD in humans. We hypothesize that genetic variants may be associated with SCD in animals, including horses. Genetic variants are transmitted to offspring and their frequency might increase within a family. Therefore, the frequency of such variants might increase with the inbreeding factor. Higher inbreeding could have a negative impact on racing performance. Pedigree data and career earnings from racehorses diagnosed with SCD between 2002 and 2017 were compared using non-parametric tests with 1) control horses that died due to catastrophic musculoskeletal injuries and 2) horses that raced during the same period without reported problems. Diagnosis of SCD was based on necropsy reports, including macroscopic and microscopic examinations. Death was registered in the study period for 61 horses. Eleven of these horses were excluded due to missing autopsy reports. In 25 cases, the diagnosis remained unknown and death was possibly caused by cardiac arrhythmia, in two cases cardiac disease was identified, in seven cases a rupture of a major vessel had occurred. In addition, 16 horses died or were euthanized due to severe musculoskeletal injuries. No significant differences in inbreeding coefficients or in career earnings were found between the groups or between horses with EASD compared with other horses racing during the same period. The study provides no evidence for increased inbreeding factor in Finnish racehorses with SCD.

Ataluren-Promising Therapeutic Premature Termination Codon Readthrough Frontrunner

Around 12% of hereditary disease-causing mutations are in-frame nonsense mutations. The expression of genes containing nonsense mutations potentially leads to the production of truncated proteins with residual or virtually no function. However, the translation of transcripts containing premature stop codons resulting in full-length protein expression can be achieved using readthrough agents. Among them, only ataluren was approved in several countries to treat nonsense mutation Duchenne muscular dystrophy (DMD) patients. This review summarizes ataluren’s journey from its identification, via first in vitro activity experiments, to clinical trials in DMD, cystic fibrosis, and aniridia. Additionally, data on its pharmacokinetics and mechanism of action are presented. The range of diseases with underlying nonsense mutations is described for which ataluren therapy seems to be promising. What is more, experiments in which ataluren did not show its readthrough activity are also included, and reasons for their failures are discussed.

Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.

Contributions of S- and R-citalopram to the citalopram-induced modulation of the function of Nav1.5 voltage-gated sodium channels

Citalopram, a selective serotonin reuptake inhibitor (SSRI), has been reported to have adverse effects such as cardiotoxicity, including prolongation of the QTc interval. Although citalopram is well known to be a racemic compound comprised of S-citalopram (escitalopram) and R-citalopram, it is still unclear which enantiomer is responsible for cardiotoxicity induced by citalopram. It is also unclear which biomolecule is the target that produces the adverse effect of citalopram. In this study, we investigated whether citalopram, escitalopram and R-citalopram had an electrophysiological effect on Nav1.5 voltage-gated sodium channel (VGSC) current and how their electrophysiological properties affected Nav1.5 VGSC. To examine the effects of the electrophysiological properties of them, whole-cell patch clamp recording was performed using HEK293 cells expressing human Nav1.5 VGSCs. Nav1.5 VGSC current decreased by 60.0 ± 6.3% and 55.1 ± 12.5% under treatment with 100 μM citalopram and escitalopram, respectively. However, 100 μM R-citalopram decreased Nav1.5 VGSC current by only 36.2 ± 8.7%. In addition, treatment with 100 μM citalopram and escitalopram changed the voltage-dependence of activation and induced a negative shift of the voltage of half-maximal activation compared to 100 μM R-citalopram. In contrast, treatment with 100 μM citalopram and escitalopram, but not R-citalopram, changed the voltage-dependence of inactivation, and the voltage at half-maximal inactivation slightly shifted toward negative potential. These results suggest that the adverse cardiac effect produced by citalopram might result from modification of the electrophysiological properties of Nav1.5 VGSCs, and escitalopram might contribute more to this adverse effect than R-citalopram.

[Forensic aspects of sudden autopsy-negative cardiac death]

The review of the world literature on the most common causes, mechanism of development and diagnostic signs of sudden autopsy-negative cardiac death is presented. Two groups of reasons for the development of this pathology were identified - traumatic and non-traumatic. The traumatic group includes the cardio-inhibitory reflex and the trigemino-cardiac reflex. The non-traumatic group included prolonged Q-T interval syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia. The importance of postmortem molecular genetic research in cases of sudden cardiac death in order to prevent the deaths in the victim's relatives is noted. The criteria for the diagnosis of reflex cardiac arrest are indicated.

Hydroxychloroquine Inhibits Cardiac Conduction in Aged Patients with Nonmalaria Diseases

Background

The COVID-19 pandemic has brought increased focus on hydroxychloroquine (HCQ), as doctors, the medical community, and policymakers around the world attempt to understand how the risks of HCQ weigh against unknown benefits. We aim to evaluate the effects of HCQ on cardiac conduction, thus contributing to the global understanding of implications of HCQ use.

Methods

We reviewed 717 cases of nonmalaria patients treated with HCQ (302) or without HCQ (415) in our hospital from 2008 to 2019, analyzed the cardiac conduction recorded by electrocardiogram (122 vs. 180) including heart rate (HR), PR, and corrected-QT (QTc) intervals, and explored the relationship of cardiac conduction with age, HCQ dosage, HCQ duration, sex, and primary diseases in HCQ users.

Results

The all-cause mortality is similar between HCQ and non-HCQ groups (4.0 vs. 4.3%, p = 0.85). Patients aged 45 years or older, not younger ones, have lower HR (80.1 ± 1.7 vs. 85.7 ± 1.8 bpm, p = 0.03) but longer PR (163 ± 3.4 vs. 146.6 ± 4.2 ms, p = 0.003) and QTc (417.8 ± 3.8 vs. 407.7 ± 2.7 ms, p = 0.03) in HCQ than those in non-HCQ. The age in the HCQ group is positively correlated with PR (R = 0.31, p < 0.01) and QTc (R = 0.34, p < 0.01) but not HR. HR, PR, and QTc are not related to HCQ dosage (0.1–0.6 g/day), HCQ duration (0.2–126 months), sex, primary diseases, and repeated exams.

Conclusion

Age is the most important risk factor of HCQ on cardiac conduction in nonmalaria patients. Electrocardiogram monitoring is suggested in aged patients due to the effects of HCQ on HR, PR, and QTc.

Survey concerning internal medicine physicians and prolonged QT interval: Knowledge and treatment practices

Prolongation of the QT interval is associated with adverse cardiac events specifically Torsades de pointes (TdP). There are multiple mediations that have a known, possible, or conditional risk for prolonged QT interval, but general practitioners’ knowledge of these medications is unknown. We conducted a survey to assess internal medicine (IM) providers’ knowledge of risk factors and medications associated with prolonged QT as well as provider experience and comfort when treating patients with prolonged QT. A 17-question, anonymous survey was constructed in 2019 and distributed to IM providers and residents at a tertiary care center. Questions included demographic information, 6 Likert-scale questions gauging provider experience with prolonged QT, and 10 multiple choice clinical vignettes to assess clinical knowledge. Data was analyzed descriptively. Knowledge was assessed via clinical vignettes and compared by level of training. Forty-one responses were received out of a total of 87 possible respondents (47.1% response rate). About 70% of respondents see patients with acquired prolonged QT once monthly or more. 95% rarely see congenital prolonged QT. When presented with QTc drug issues, 73% of providers seldom or sometimes consulted pharmacy, but about half used online resources. The average correct score on the clinical vignettes was 5.59/10, with the highest scores seen in attending physicians in their first five years of practice (6.96/10). Our survey suggests that IM providers commonly encounter QT prolonging drugs. Educational efforts to improve knowledge of drug and patient risk factors for TdP may be needed.

Mexiletine Shortened QT Interval and Reduced Ventricular Arrhythmias in a Pedigree of Type 2 Long QT Syndrome Combined with Left Ventricular Non-Compaction

In this study, we present a case of a 22-year-old female with a family history of syncope, suffering from recurrent syncope since childhood. She had an obvious prolonged QTc interval of up to 651 ms, a bifid T wave pattern on electrocardiogram, and torsade de pointes, corresponding to a syncope episode. Additionally, her echocardiogram showed left ventricular non-compaction in the apex. After treatment with mexiletine, the QTc interval has been observed to shorten immediately, and the T wave morphology recovered. A similar effect was also observed in her mother and young sister. Administration of propranolol prolonged her QTc interval. Target sequencing of candidate genes revealed a missense mutation in the pore area of the hERG protein, coded by KCNH2. We diagnosed this as a case of type 2 long QT syndrome in which mexiletine could be effective in shortening the QTc interval.

Long QT syndrome - Bench to bedside

Long QT syndrome (LQTS) is a cardiovascular disorder characterized by an abnormality in cardiac repolarization leading to a prolonged QT interval and T-wave irregularities on the surface electrocardiogram. It is commonly associated with syncope, seizures, susceptibility to torsades de pointes, and risk for sudden death. LQTS is a rare genetic disorder and a major preventable cause of sudden cardiac death in the young. The availability of therapy for this lethal disease emphasizes the importance of early and accurate diagnosis. Additionally, understanding of the molecular mechanisms underlying LQTS could help to optimize genotype-specific treatments to prevent deaths in LQTS patients.

In this review, we briefly summarize current knowledge regarding molecular underpinning of LQTS, in particular focusing on LQT1, LQT2, and LQT3, and discuss novel strategies to study ion channel dysfunction and drug-specific therapies in LQT1, LQT2, and LQT3 syndromes.

Intravenous lipid emulsion as an adjuvant therapy of acute clozapine poisoning

Introduction:

Clozapine is a frequently prescribed atypical antipsychotic drug. Various case reports documented the successful recovery of acute antipsychotics toxicity in association with the administration of intralipid emulsion (ILE).

Aim:

This study aimed to assess the adjuvant therapeutic role of SMOF Lipid administration on the outcomes of acute clozapine poisoning.

Methods:

Forty patients with acute clozapine poisoning were randomly allocated into two equal groups. The control group received the standard supportive treatment only, whereas the intervention group received the standard supportive treatment plus SMOF Lipid 20% infusion. All patients were subjected to history taking, full clinical examination, and laboratory investigations. The study outcomes were evaluated.

Results:

The mean Glasgow Coma Scale (GCS) at 6 hours (13.1 ± 2.3 vs 9.2 ± 2, p < 0.001) and 12 hours (14.3 ± 1.5 vs 9.6 ± 2, p < 0.001) after admission was significantly higher in the intervention group compared to the control group. The intervention group showed a significantly lower frequency of prolonged QTc interval 12 hours after admission (p = 0.003), as well as a significantly shorter hospital stay (p < 0.001).

Conclusions:

SMOF Lipid infusion seemed to have improved GCS, the prolonged QTc interval, and shortened the length of hospital stay. Furthermore, there were no adverse effects related to its administration.

Early Identification of Prolonged QT Interval for Prevention of Sudden Infant Death

Introduction: Long QT syndrome is the main arrhythmogenic disease responsible for sudden death in infants, especially in the first days of life. Performing an electrocardiogram in newborns could enable early diagnosis and adoption of therapeutic measures focused on preventing lethal arrhythmogenic events. However, the inclusion of an electrocardiogram in neonatal screening protocols still remains a matter of discussion. To comprehensively analyse the potential clinical value of performing an electrocardiogram and subsequent follow-up in a cohort of newborns. Methods: Electrocardiograms were performed in 685 neonates within the first week of life. One year follow-up was performed if QTc > 450 ms identified. Comprehensive genetic analysis using massive sequencing was performed in all cases with QTc > 470 ms. Results: We identified 54 neonates with QTc > 450 ms/ <470 ms; all normalized QTc values within 6 months. Eight cases had QTc > 480 ms at birth and, if persistent, pharmacological treatment was administrated during follow-up. A rare variant was identified as the potential cause of long QT syndrome in five cases. Three cases showed a family history of sudden arrhythmogenic death. Conclusions: Our prospective study identifies 0.14% of cases with a definite long QT, supporting implementation of electrocardiograms in routine pediatric protocols. It is an effective, simple and non-invasive approach that can help prevent sudden death in neonates and their relatives. Genetic analyses help to unravel the cause of arrhythmogenic disease in diagnosing neonates. Further, clinical assessment and genetic analysis of relatives allowed early identification of family members at risk of arrhythmias helping to adopt preventive personalized measures.

Long Noncoding RNAs in Cardiac Development

The exquisite transcriptional control of developmental gene programs is critical for hardwiring the complex expression patterns that govern cell-fate determination and differentiation during heart development. During the past several years, studies have illuminated our understanding of a complex noncoding transcriptional landscape, primarily associated with long noncoding RNAs (lncRNAs), that is implicated in these developmental processes and has begun to reveal key functions of these transcripts. In this review, we discuss the expanding roles for lncRNAs in the earliest points of cardiac development and through differentiation and maturation of multiple cell types within the adult heart. We go on to outline the diverse mechanisms by which cardiovascular lncRNAs orchestrate these transcriptional programs, explore the challenges linked to the study of lncRNAs in developmental phenotypes, and summarize the implications for these molecules in human cardiovascular disorders.

Treadmill exercise testing improves diagnostic accuracy in children with concealed congenital long QT syndrome

BACKGROUND

Resting electrocardiogram (ECG) identification of long QT syndrome (LQTS) has limitations. Uncertainty exists on how to classify patients with borderline prolonged QT intervals. We tested if exercise testing could help serve to guide which children with borderline prolonged QT intervals may be gene positive for LQTS.

METHODS

Pediatric patients (n = 139) were divided into three groups: Controls (n = 76), gene positive LQTS with borderline QTc (n = 21), and gene negative patients with borderline QTc (n = 42). Borderline QTc was defined between 440-470 (male) and 440-480 (female) ms. ECGs were recorded supine, sitting, and standing. Patients then underwent treadmill stress testing with Bruce protocol followed by a 9-minute recovery phase.

RESULTS

Supine resting QTc, age, and Schwartz score for the three groups were: (a) gene positive: 446 ± 23 ms, 12.4 ± 3.4 years old, 3.2 ± 1.8; (b) gene negative: 445 ± 20 ms, 12.1 ± 2 years old, 2.0 ± 1.2; and (c) control: 400 ± 24 ms, 15.0 ± 3 years old. The three groups could be differentiated by their QTc response at two time points: standing and recovery phase at 6 minutes. Standing QTc ≥460 ms differentiated borderline prolonged QTc patients (gene positive and gene negative) from controls. Late recovery QTc ≥480 ms distinguished gene positive from gene negative patients.

CONCLUSION

Exercise stress testing can be useful to identify children who are gene positive borderline LQTS from a normal population and gene negative borderline QTc children, allowing for selective gene testing in a higher risk group of patients with borderline QTc intervals and intermediate Schwartz scores.

Promise and Potential Peril With Lumacaftor for the Trafficking Defective Type 2 Long-QT Syndrome-Causative Variants, p.G604S, p.N633S, and p.R685P, Using Patient-Specific Re-Engineered Cardiomyocytes

BACKGROUND

The KCNH2-encoded Kv11.1 hERG (human ether-a-go-go related gene) potassium channel is a critical regulator of cardiomyocyte action potential duration (APD). The majority of type 2 long-QT syndrome (LQT2) stems from trafficking defective KCNH2 mutations. Recently, Food and Drug Administration-approved cystic fibrosis protein trafficking chaperone, lumacaftor, has been proposed as novel therapy for LQT2. Here, we test the efficacy of lumacaftor treatment in patient-specific induced pluripotent stem cell-cardiomyocytes (iPSC-CMs) derived from 2 patients with known LQT2 trafficking defective mutations and a patient with novel KCNH2 variant, p.R685P.

METHODS

Patient-specific iPSC-CM models of KCNH2-G604S, KCNH2-N633S, and KCNH2-R685P were generated from 3 unrelated patients diagnosed with severe LQT2 (rate-corrected QT>500 ms). Lumacaftor efficacy was also tested by ANEPPS, FluoVolt, and ArcLight voltage dye-based APD90 measurements.

RESULTS

All 3 mutations were hERG trafficking defective in iPSC-CMs. While lumacaftor treatment failed to rescue the hERG trafficking defect in TSA201 cells, lumacaftor rescued channel trafficking for all mutations in the iPSC-CM model. All 3 mutations conferred a prolonged APD90 compared with control. While lumacaftor treatment rescued the phenotype of KCNH2-N633S and KCNH2-R685P, lumacaftor paradoxically prolonged the APD90 in KCNH2-G604S iPSC-CMs. Lumacaftor-mediated APD90 rescue was affected by rapidly activating delayed rectifier K+ current blocker consistent with the increase of rapidly activating delayed rectifier K+ current by lumacaftor is the underlying mechanism of the LQT2 rescue.

CONCLUSIONS

While lumacaftor is an effective hERG channel trafficking chaperone and may be therapeutic for LQT2, we urge caution. Without understanding the functionality of the mutant channel to be rescued, lumacaftor therapy could be harmful.

Targeting the β-adrenergic receptor in the clinical management of congenital long QT syndrome

The long QT syndrome (LQTS) is largely treated pharmacologically with β-blockers, despite the role of sympathetic activity in LQTS being poorly understood. Using the trigger-substrate model of cardiac arrhythmias in this review, we amalgamate current experimental and clinical data from both animal and human studies to explain the mechanism of adrenergic stimulation and blockade on LQT arrhythmic risk and hence assess the efficacy of β-adrenoceptor blockade in the management of LQTS. In LQTS1 and LQTS2, sympathetic stimulation increases arrhythmic risk by enhancing early afterdepolarizations and transmural dispersion of repolarization. β-Blockers successfully reduce cardiac events by reducing these triggers and substrates; however, these effects are less marked in LQTS2 compared with LQTS1. In LQTS3, clinical and experimental investigations of the effects of sympathetic stimulation and β-blocker use have produced contradictory findings, resulting in significant clinical uncertainty. We offer explanations for these contradicting results relating to study sample size, the dose of the β-blocker administered associated with its off-target Na⁺ channel effects, as well as the type of β-blocker used. We conclude that the antiarrhythmic efficacy of β-blockers is a genotype-specific phenomenon, and hence the use of β-blockers in clinical practice should be genotype dependent.

Concealed congenital long QT syndrome during velopharyngeal dysfunction correction: a case report

The congenital long QT syndrome (LQTS) is an inherited cardiac disorder characterized by increased QT intervals and a tendency to experience ventricular tachycardia, which can cause fainting, heart failure, or sudden death. A 4-year-old female patient undergoing velopharyngeal correction surgery under general anesthesia suddenly developed Torsades de pointes. Although the patient spontaneously resolved to sinus rhythm without treatment, subsequent QT prolongation persisted. Here, we report a case of concealed LQTS with a literature review.

Frequency of KCNQ1 variants causing loss of methylation of Imprinting Centre 2 in Beckwith-Wiedemann syndrome

Background

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder caused by disturbances of the chromosomal region 11p15.5. The most frequent molecular finding in BWS is loss of methylation (LOM) of the Imprinting Centre 2 (IC2) region on the maternal allele, which is localised in intron 10 of the KCNQ1 gene. In rare cases, LOM of IC2 has been reported in families with KCNQ1 germline variants which additionally cause long-QT syndrome (LQTS). Thus, a functional link between disrupted KCNQ1 transcripts and altered IC2 methylation has been suggested, resulting in the co-occurrence of LQTS and BWS in case of maternal inheritance. Whereas these cases were identified by chance or in patients with abnormal electrocardiograms, a systematic screen for KCNQ1 variants in IC2 LOM carriers has not yet been performed.

Results

We analysed 52 BWS patients with IC2 LOM to determine the frequency of germline variants in KCNQ1 by MLPA and an amplicon-based next generation sequencing approach. We identified one patient with a splice site variant causing premature transcription termination of KCNQ1.

Conclusions

Our study strengthens the hypothesis that proper KCNQ1 transcription is required for the establishment of IC2 methylation, but that KCNQ1 variants cause IC2 LOM only in a small number of BWS patients.

KCNQ2-Neonatal Epileptic Encephalopathy Complicated by Ventricular Tachycardia: A Case Report

Introduction: Mutations in KCNQ2 are related to a spectrum of neonatal epileptic phenotypes. Here we report a case of KCNQ2-related neonatal epileptic encephalopathy (KCNQ2-NEE) that is complicated by an incidentally found ventricular tachycardia. Case Presentation: An infant boy presented with very early onset refractory focal tonic seizures and developmental delay, and was diagnosed with epilepsy. Trio-whole exome sequencing identified a previously reported de novo mutation in KCNQ2 [c.794C>T; p. (Ala265Val)], a known pathogenic variant for KCNQ2-NEE. Interestingly, ventricular tachycardia was incidentally found on electrocardiography. Conclusions: We here suggest the possibility of a potential electrophysiologic link between the two phenotypes and that they may be attributable to the same de novo mutation.

Identification of potential candidate genes and pathways in atrioventricular nodal reentry tachycardia by whole-exome sequencing

Background

Atrioventricular nodal reentry tachycardia (AVNRT) is the most common manifestation of paroxysmal supraventricular tachycardia (PSVT). Increasing data have indicated familial clustering and participation of genetic factors in AVNRT, and no pathogenic genes related to AVNRT have been reported.

Methods

Whole‐exome sequencing (WES) was performed in 82 patients with AVNRT and 100 controls. Reference genes, genome‐wide association analysis, gene‐based collapsing, and pathway enrichment analysis were performed. A protein‐protein interaction (PPI) network was then established; WES database in the UK Biobank and one only genetic study of AVNRT in Denmark were used for external data validation.

Results

Among 95 reference genes, 126 rare variants in 48 genes were identified in the cases (minor allele frequency < 0.001). Gene‐based collapsing analysis and pathway enrichment analysis revealed six functional pathways related to AVNRT as with neuronal system/neurotransmitter release cycles and ion channel/cardiac conduction among the top 30 enriched pathways, and then 36 candidate pathogenic genes were selected. By combining with PPI analysis, 10 candidate genes were identified, including RYR2, NOS1, SCN1A, CFTR, EPHB4, ROBO1, PRKAG2, MMP2, ASPH, and ABCC8. From the UK Biobank database, 18 genes from candidate genes including SCN1A, PRKAG2, NOS1, and CFTR had rare variants in arrhythmias, and the rare variants in PIK3CB, GAD2, and HIP1R were in patients with PSVT. Moreover, one rare variant of RYR2 (c.4652A > G, p.Asn1551Ser) in our study was also detected in the Danish study. Considering the gene functional roles and external data validation, the most likely candidate genes were SCN1A, PRKAG2, RYR2, CFTR, NOS1, PIK3CB, GAD2, and HIP1R.

Conclusion

The preliminary results first revealed potential candidate genes such as SCN1A, PRKAG2, RYR2, CFTR, NOS1, PIK3CB, GAD2, and HIP1R, and the pathways mediated by these genes, including neuronal system/neurotransmitter release cycles or ion channels/cardiac conduction, might be involved in AVNRT.

Nausea and Vomiting: a Palliative Care Imperative

PURPOSE OF REVIEW

This review was undertaken to survey recent literature for research reports and comprehensive clinical reviews addressing the pharmacologic management of nausea and vomiting (N&V) in advanced cancer. The goal was to integrate findings in a comprehensive article that incorporates palliative care concepts into antiemetic treatment.

RECENT FINDINGS

There are few published studies of N&V in advanced cancer; such research may be limited by the multicausal nature of N&V and participant burden to patients with life-limiting disease. Most articles are written by oncologists who also specialize in palliative care, and those addressing adverse effects of drugs used as antiemetics are found in other literature. Articles addressing more novel therapies, like cannabinoids and medical marijuana, are uncommon in the oncology literature. N&V in patients with progressive or advanced cancer is often multicausal. Nausea is more common and persistent, and even mild nausea is bothersome and may cause anxiety or depression. The mechanisms of nausea and vomiting overlap, but different neural pathways constitute the final pathway for each-the brainstem for vomiting and higher brain regions for nausea. Common causes of N&V in advanced cancer include constipation, opioids, and malignant bowel obstruction. About 40% have undetermined causes and may be exacerbated by impaired gastric emptying, chemical imbalances, or other factors. Several drugs that have antiemetic effects and act at different receptors are used to palliate N&V. There is a paucity of research that supports palliative antiemetic choices, and other research is needed to define potential therapeutic strategies that capitalize on differences between nausea and vomiting.

The ketogenic diet and the QT interval

Long QT syndrome is a disorder of ventricular myocardial repolarization associated with an increased risk of life-threatening cardiac arrhythmias and sudden cardiac death. This report highlights a case of QT prolongation with torsades de pointes in a patient with baseline congenital long QT syndrome, believed to be precipitated by metabolic changes associated with the "ketogenic diet."

Recurrent syncope in a child and video assisted thoracoscopic surgery - The long and short of it

Long QT syndrome (LQTS) is a myocardial repolarisation disorder caused by cardiac ion channelopathy and one of its common presentations is recurrent syncope. This reduced repolarisation reserve in LQTS can be unmasked by perioperative factors like electrolyte imbalance, drugs, hypothermia and changes in cardiac autonomic tone. We report the anaesthetic management of left thoracoscopic sympathectomy in a 5-year-old child with LQTS and epicardial pacemaker in situ. It is very challenging to isolate the lung on one hand and prevent the predisposition to torsadogenic potential on the other.

Genetic Therapies for Hearing Loss: Accomplishments and Remaining Challenges

More than 15 years have passed since the official completion of the Human Genome Project. Predominantly due to this project, over one hundred genes have now been linked to hearing loss. Although major advancements have been made in the understanding of underlying pathologies in deafness as a consequence of these gene discoveries, biological treatments for these conditions are still not available and current treatments rely on amplification or prosthetics. A promising approach for developing treatments for genetic hearing loss is the most simplistic one, that of gene therapy. Gene therapy would intuitively be ideal for these conditions since it is directed at the very source of the problem. Recent achievements in this field in laboratory models spike hope and optimism among scientists, patients, and industry, and suggest that this approach can mature into clinical trials in the coming years. Here we review the existing literature and discuss the different aspects of developing gene therapy for genetic hearing loss.

Severe transient neonatal long QT syndrome due to maternal paroxetine usage: a case report

A female neonate with in utero selective serotonin reuptake inhibitor exposure presented with bradycardia shortly after birth. Electrocardiography showed severe QT prolongation and second-degree atrioventricular block. Over time QT-times spontaneously normalised and genetic testing did not show mutations associated with long QT syndrome making maternal selective serotonin reuptake inhibitor usage the most likely explanation for the observed severe transient neonatal QT prolongation.

Animal- and human-based evidence for the protective effects of stem cell therapy against cardiovascular disorders

The increasing rate of mortality and morbidity because of cardiac diseases has called for efficient therapeutic needs. With the advancement in cell-based therapies, stem cells are abundantly studied in this area. Nearly, all sources of stem cells are experimented to treat cardiac injuries. Tissue engineering has also backed this technique by providing an advantageous platform to improve stem cell therapy. After in vitro studies, primary treatment-based research studies comprise small and large animal studies. Furthermore, these studies are implemented in human models in the form of clinical trials. Purpose of this review is to highlight the animal- and human-based studies, exploiting various stem cell sources, to treat cardiovascular disorders.

Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis

Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.