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The transient outward current (Ito) that mediates early (phase 1) repolarization is conducted by theKCND3-V392I was identified in an 18-year-old male with J wave syndrome/early repolarization syndrome, and a history of cardiac arrest including ventricular tachycardia/ventricular fibrillation and atrial fibrillation/atrial flutter. PathogenicKCND3-V392I demonstrated a marked gain-of-function phenotype, increasing peak IThis preclinical study provides pharmacological and functional evidence to suggest that Acacetin may be a novel therapeutic for patients with KCND3 gain-of-function-associated J wave syndrome by inhibiting I

J wave syndrome (JWS) is an inherited cardiac channelopathy associated with malignant ventricular arrhythmias and sudden cardiac death (SCD), which comprises early repolarization syndrome and Brugada syndrome. Here, we explore the association between variants in the L -type calcium channel gene subunits, α 1C ( CACNA1C ) and β2b ( CACNB2b ), and the JWS phenotype. Using next-generation genetic sequencing of 402 JWS probands and their family members, we identified a CACNA1C -G37R (p.Gly37Arg) mutation in five individuals in four families, two of which had a family history of SCD as well as a CACNB2b -S143F (p.Ser143Phe) mutation in seven individuals in three families, two of which had a family history of SCD. The variants were located in exon 2 in CACNA1C and exon 5 in CACNB2b ; both were in highly conserved amino acid residues. Whole-cell patch-clamp results showed that compared with the wild-type group, calcium current density of CACNB2b- S143F and CACNA1C -G37R were significantly lower displaying a dominant-negative effect. Our findings provide further support for the hypothesis that variants in CACNA1C and CACNB2b are associated with JWS. The results suggest that mutations in these two genes lead to loss-of-function of the cardiac calcium channel current warranting their inclusion in genetic screening protocols. This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.

Atrial fibrillation (AF) is a very common cardiac arrhythmia with an estimated prevalence of 33.5 million patients globally. It is associated with an increased risk of death, stroke and peripheral embolism. Although genetic studies have identified a growing number of genes associated with AF, the definitive impact of these genetic findings is yet to be established. Several mechanisms, including electrical, structural and neural remodelling of atrial tissue, have been proposed to contribute to the development of AF. Despite over a century of exploration, the molecular and cellular mechanisms underlying AF have not been fully established. Current antiarrhythmic drugs are associated with a significant rate of adverse events and management of AF using ablation is not optimal, especially in cases of persistent AF. This review discusses recent advances in our understanding and management of AF, including new concepts of epidemiology, genetics and pathophysiological mechanisms. We review the current status of antiarrhythmic drug therapy for AF, new potential agents, as well as mechanism-based AF ablation. This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.

Background: The transient outward current (Ito) that mediates early (phase 1) repolarization is conducted by the KCND3 -encoded Kv4.3 pore-forming α-subunit. KCND3 gain-of-function mutations have been reported previously as a pathogenic substrate for J wave syndromes (JWS), including the Brugada syndrome and early repolarization syndrome, as well as autopsy-negative sudden unexplained death (SUD). Acacetin, a natural flavone, is a potent Ito current blocker. Acacetin may be a novel therapeutic for KCND3 -mediated J wave syndrome. Methods: KCND3-V392I was identified in an 18-year-old male with J wave syndrome/early repolarization syndrome, and a history of cardiac arrest including ventricular tachycardia/ventricular fibrillation and atrial fibrillation/atrial flutter. Pathogenic KCND3 mutation was engineered by site-directed mutagenesis and co-expressed with wild-type KChIP2 in TSA201 cells. Gene-edited/variant-corrected isogenic control and patient-specific pluripotent stem cell–derived cardiomyocytes (iPSC-CMs) from the p. Val392Ile-KCND3-positive patient were generated. I to currents and action potentials were recorded before and after treatment with Acacetin using the whole cell patch-clamp and multielectrode array technique. Western blot and immunocytochemistry were performed to investigate KCND3 expression. Results: KCND3-V392I demonstrated a marked gain-of-function phenotype, increasing peak I to current density by 92.2% ( P P P P Conclusions: This preclinical study provides pharmacological and functional evidence to suggest that Acacetin may be a novel therapeutic for patients with KCND3 gain-of-function-associated J wave syndrome by inhibiting I to and abolishing the accentuated action potential notch in patient-derived iPSC-CMs.

El haz muscular apicobasal (HAB) del ventriculo izquierdo (VI) es un posible marcador morfologico de miocardiopatia hipertrofica (MCH), adicional a otras expresiones fenotipicas asociadas a la enfermedad, como criptas miocardicas, alteraciones en la valvula mitral, la arquitectura muscular papilar o la morfologia ventricular derecha1, ademas de la propia hipertrofia del VI2. La HAB se extiende desde la region apical a la porcion mas basal del septum o de la pared anterior.

Background. We report an inherited cardiac arrhythmia syndrome consisting of Brugada and Early Repolarization Syndrome associated with variants in SCN9A, PXDNL, and FKBP1B. the proband inherited the 3 mutations and exhibited palpitations and arrhythmia-mediated syncope, whereas the parents and sister, who carried one or two of the mutations, were asymptomatic. Methods and Results. We assessed the functional impact of these mutations in induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) derived from the proband and an unaffected family member. Current and voltage clamp recordings, as well as confocal microscopy analysis of Ca2+ transients, were evaluated in hiPSC-CMs from the proband and compared these results with hiPSC-CMs from undiseased controls. Genetic analysis using next-generation DNA sequencing revealed heterozygous mutations in SCN9A, PXDNL, and FKBP1B in the proband. the proband displayed right bundle branch block and exhibited episodes of syncope. the father carried a mutation in FKBP1B, whereas the mother and sister carried the SCN9A mutation. None of the 3 family members screened developed cardiac events. Action potential recordings from control hiPSC-CM showed spontaneous activity and a low upstroke velocity. in contrast, the hiPSC-CM from the proband showed irregular spontaneous activity. Confocal microscopy of the hiPSC-CM of the proband revealed low fluorescence intensity Ca2+ transients that were episodic in nature. Patch-clamp measurements in hiPSC-CM showed no difference in I-Na but reduced ICa in the proband compared with control. Coexpression of PXDNL-R391Q with SCN5A-WT displayed lower I-Na density compared to PXDNLWT. in addition, coexpression of PXDNL-R391Q with KCND3-WT displayed significantly higher I-to density compared to PXDNL-WT. Conclusion. SCN9A, PXDNL, and FKBP1B variants appeared to alter spontaneous activity in hiPSC-CM. Only the proband carrying all 3 mutations displayed the ERS/BrS phenotype, whereas one nor two mutations alone did not produce the clinical phenotype. Our results suggest a polygenic cause of the BrS/ERS arrhythmic phenotype due to mutations in these three gene variants caused a very significant loss of function of I-Na and I-Ca and gain of function of I-to., NHLBIUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Heart Lung & Blood Institute (NHLBI) [HL47678, HL138103, HL152201]; Martha and Wistar Morris Fund; W/W. Smith Trust; National Natural Science Foundation Project of ChinaNational Natural Science Foundation of China (NSFC) [81670304]; Free and Accepted Mason of New York; Free and Accepted Mason of Florida; Free and Accepted Mason of Massachusetts; Free and Accepted Mason of Connecticut; Free and Accepted Mason of Maryland; Free and Accepted Mason of Wisconsin; Free and Accepted Mason of Washington; Free and Accepted Mason of Rhode Island; [HL145530-01A1], Drs. Antzelevitch and Barajas acknowledge support from NHLBI (HL47678, HL138103, and HL152201), the Martha and Wistar Morris Fund, and the W/W. Smith Trust. Dr. Hu acknowledges support by the National Natural Science Foundation Project of China (Grant no. 81670304), distinguished professor of Chutian Scholar Program of Hubei Province. Dr. Cordeiro acknowledges support from HL145530-01A1 and the Free and Accepted Masons of New York, Florida, Massachusetts, Connecticut, Maryland, Wisconsin, Washington, and Rhode Island.

Introduction: Early repolarization syndrome (ERS) is an inherited sudden cardiac death syndrome. Hypothesis: In this study we test the role of genetic variants in cardiac calcium channel genes in the pathogenesis of ERS and probes the underlying mechanisms. Methods: PCR-based next-generation sequencing was carried out using a targeted gene approach. Unrelated ERS probands carrying calcium channel variants were evaluated clinically and compared with matched healthy controls. Wild type (WT) and mutant CACNA1C genes were co-expressed with CACNB2b and CACNA2D1 in HEK293 cells and studied using whole-cell patch-clamp and confocal fluorescence microscope . Results: Among 104 ERS probands, 16 carried pathogenic variants in calcium channel genes (32.2±14.6 years old, 87.5% male). The symptoms at diagnosis included syncope (56.3%), ventricular tachycardia/fibrillation (VT/VF, 62.5%), sudden cardiac death (SCD, 56.3%). Three cases (18.8%) had a family history of SCD or syncope. Eight patients (50.0%) had a single calcium gene rare variant. The other half carried rare variants in other ERS susceptible genes. Compared with controls, the heart rate was slower (72.7±8.9 vs. 65.6±16.1 bpm), QTc interval was shorter (408.2±21.4 vs. 386.8±16.9 ms) and Tp-e/QT was longer (0.22±0.05 vs.0.28±0.04) in calcium mutation carriers. Electrophysiological analysis of one mutation, CACNA1C -P817S revealed that the density of I Ca was reduced by approximately 84.6% compared to WT (-3.1±2.5 vs. -20.5±3.6 pA/pF, n=11 and 15, respectively). Heterozygous expression of mutant channels was associated with a 51.3% reduction of I Ca . Steady-state inactivation was shifted to more negative potentials and significantly accelerated. Confocal microscopy revealed trafficking impairment of CACNA1C -P817S (peripheral/central intensity: 0.94±0.1 in WT vs. 0.33±0.1 in P817S, n=10 and 9, respectively). Conclusions: ERS associated with loss of function (LOF) genetic defects in genes encoding the cardiac calcium channel represents a unique clinical entity characterized by decreased heart rate and QTc, as well as increased transmural dispersion of repolarization. In the case of CACNA1C -P817S impaired trafficking of the channel to the membrane contributes to the LOF.

Background Oliceridine is a biased ligand at the μ-opioid receptor recently approved for the treatment of acute pain. In a thorough QT study, corrected QT (QTc) prolongation displayed peaks at 2.5 and 60 minutes after a supratherapeutic dose. The mean plasma concentration peaked at 5 minutes, declining rapidly thereafter. Objective The purpose of this study was to examine the basis for the delayed effect of oliceridine to prolong the QTc interval. Methods Repolarization parameters and tissue accumulation of oliceridine were evaluated in rabbit left ventricular wedge preparations over a period of 5 hours. The effects of oliceridine on ion channel currents were evaluated in human embryonic kidney and Chinese hamster ovary cells. Quinidine was used as a control. Results Oliceridine and quinidine produced a progressive prolongation of the QTc interval and action potential duration over a period of 5 hours, paralleling slow progressive tissue uptake of the drugs. Oliceridine caused modest prolongation of these parameters, whereas quinidine produced a prominent prolongation of action potential duration and QTc interval as well as development of early afterdepolarization (after 2 hours), resulting in a high torsades de pointes score. The 50% inhibitory concentration values for the oliceridine inhibition of the rapidly activating delayed rectifier current (human ether a-go-go current) and late sodium channel current were 2.2 and 3.45 μM when assessed after traditional acute exposure but much lower after 3 hours of drug exposure. Conclusion Our findings suggest that a gradual increase of intracellular access of drugs to the hERG channels as a result of their intracellular uptake and accumulation can significantly delay effects on repolarization, thus confounding the assessment of QT interval prolongation and arrhythmic risk when studied acutely. The multi-ion channel effects of oliceridine, late sodium channel current inhibition in particular, point to a low risk of devloping torsades de pointes.

Genome-wide association studies indicate that SCN10A plays an important role in cardiac electrophysiology. Common and rare SCN10A variants are suggested to contribute to Brugada Syndrome (BrS), an inherited channelopathy resulting from genetic-determined loss-of-function in cardiac sodium channel. This study sought to characterize the role of SCN10A common variants in BrS. Clinical and genetic analyses were performed in 197 patients diagnosed with BrS. Baseline ECG parameters were evaluated in patients carrying each of four common variants associated with BrS. Cellular electrophysiological study was performed in SCN5A-SCN10A co-transfected TSA201 cells to investigate the possible electrophysiological characteristics of the allele of rs6795970, which displayed the most significant association with BrS. Four SCN10A common variants (rs7630989, rs57326399, rs6795970, rs12632942) displayed significant association with BrS susceptibility. There were no evident associations between baseline ECG parameters in BrS patients and the different genotypes of the four variants. Rs6795970 (V1073) was strongly associated with a risk for BrS, which suggests the different electrophysiological characters between these two alleles. Functional study showed a positive shift in steady-state activation (V1/2: −62.2 ± 2.6 vs. –53.5 ± 1.6 for A1073 and V1073 group, respectively; P

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are used for genetic models of cardiac diseases. We report an arrhythmia syndrome consisting of Early Repolarization Syndrome (ERS) and Short QT Syndrome (SQTS). The index patient (MMRL1215) developed arrhythmia-mediated syncope after electrocution and was found to carry six mutations. Functional alterations resulting from these mutations were examined in patient-derived hiPSC-CMs. Electrophysiological recordings were made in hiPSC-CMs from MMRL1215 and healthy controls. ECG analysis of the index patient showed slurring of the QRS complex and QTc = 326 ms. Action potential (AP) recordings from MMRL1215 myocytes showed slower spontaneous activity and AP duration was shorter. Field potential recordings from MMRL1215 hiPSC-CMs lack a “pseudo” QRS complex suggesting reduced inward current(s). Voltage clamp analysis of ICa showed no difference in the magnitude of current. Measurements of INa reveal a 60% reduction in INa density in MMRL1215 hiPSC-CMs. Steady inactivation and recovery of INa was unaffected. mRNA analysis revealed ANK2 and SCN5A are significantly reduced in hiPSC-CM derived from MMRL1215, consistent with electrophysiological recordings. The polygenic cause of ERS/SQTS phenotype is likely due to a loss of INa due to a mutation in PKP2 coupled with and a gain of function in IK,ATP due to a mutation in ABCC9.

Background and Purpose Hypokalaemia is the most common electrolyte disturbance with a significant mortality due to the occurrence of ventricular arrhythmia. There is currently no available treatment to prevent ventricular arrhythmia in patients susceptible to hypokalaemia, such as those with heart failure. Potassium supplementation alone is not sufficient to alter mortality. QT prolongation and intracellular Ca2+ loading with subsequent diastolic Ca2+ release via ryanodine receptors (RyR2) are considered the predominant arrhythmogenic mechanisms in hypokalaemia-induced ventricular arrhythmia. We investigated the antiarrhythmic actions of two RyR2 inhibitors: dantrolene and VKII-86, a carvedilol analogue with no β-blocking activity, in hypokalaemia. Methods Surface ECG and ventricular action potentials (APs) were recorded from whole-heart murine Langendorff preparations. Ventricular arrhythmia incidence was compared in hearts perfused with low [K+], and those pre-treated with dantrolene or VKII-86. Whole-cell patch clamping was used in murine and canine ventricular cardiomyocytes to study the effects of dantrolene and VK-II-86 on AP parameters in normal and low [K+] and the effects of VK-II-86 on the inward rectifier current (IK1), late sodium current (INa_L) and the L-type Ca2+ current (ICa). Effects of VKII-86 on IKr were investigated in HEK-293 cells transfected with KCNH2. Results Dantrolene significantly reduced the incidence of ventricular arrhythmias induced by low [K+] in explanted murine hearts by 94%, whereas VKII-86 prevented all arrhythmias, p Conclusions and Implications VKII-86 prevents hypokalaemia-induced arrhythmogenesis by normalising intracellular calcium homeostasis and repolarization reserve. The fact that VKII-86 does not have beta-blocking activity and does not alter AP parameters in normal [K+] is promising for future tolerability and electrophysiological drug safety testing, respectively. This unique pharmacological profile may provide an exciting treatment option in hypokalaemia and other arrhythmias caused by delayed repolarization or Ca2+ overload such as heart failure and the Long QT Syndromes. Conflict of Interest None

Background Peripheral neuropathy is one of the most common late complications of diabetes. Vascular endothelial growth factor (VEGF) gene polymorphisms have been associated with the development of peripheral neuropathy in different populations of patients with type 2 diabetes mellitus (DM2). Objective To analyze the prevalence of the +936 C/T VEGF gene polymorphism among patients with DM2 with and without peripheral neuropathy. Study design and methodology 218 unrelated DM2 patients, 90 with and 128 without peripheral neuropathy were genotyped for the +936 C/T VEGF gene polymorphism using PCR amplification followed by restriction length polymorphism analysis. Results The CC homozygous VEGF+936 C/T (rs3025039) was the predominant genotype in DM2 patients with peripheral neuropathy, whereas the predominant genotype in patients without neuropathy was the heterozygous C/T. No statistical association was found between genotype distribution and the presence of neuropathy (p = 0.063). The distribution of the genotypes according to the dominant (CC vs. CT + TT) and recessive (TT vs. CT + CC) models showed that the homozygous CC and TT genotypes, respectively, are not risk factors for neuropathy. The CT genotype conferred a protective effect as seen in the over-dominant model (CT vs. CC + TT) (OR = 0.52; 95% CI = 0.300–0.90; p = 0.019). Conclusion We conclude that the VEGF+936 C/T (rs3025039) gene polymorphisms are related to peripheral neuropathy in Mexican DM2 patients, with the heterozygous genotype potentially conferring a protective effect.

Background Two major forms of inherited J-wave syndrome (JWS) are recognized: early repolarization syndrome (ERS) and Brugada syndrome (BrS). Objectives This study sought to assess the distinct features between patients with ERS and BrS carrying pathogenic variants in SCN5A. Methods Clinical evaluation and next-generation sequencing were performed in 262 probands with BrS and 104 with ERS. Nav1.5 and Kv4.3 channels were studied with the use of patch-clamp techniques. A computational model was used to investigate the protein structure. Results The SCN5A+ yield in ERS was significantly lower than in BrS (9.62% vs 22.90%; P = 0.004). Patients diagnosed with ERS displayed shorter QRS and QTc than patients with BrS. More than 2 pathogenic SCN5A variants were found in 5 probands. These patients displayed longer PR intervals and QRS duration and experienced more major arrhythmia events (MAE) compared with those carrying only a single pathogenic variant. SCN5A-L1412F, detected in a fever-induced ERS patient, led to total loss of function, destabilized the Nav1.5 structure, and showed a dominant-negative effect, which was accentuated during a febrile state. ERS-related SCN5A-G452C did not alter the inward sodium current (INa) when SCN5A was expressed alone, but when coexpressed with KCND3 it reduced peak INa by 44.52% and increased the transient outward potassium current (Ito) by 106.81%. Conclusions These findings point to SCN5A as a major susceptibility gene in ERS as much as it is in BrS, whereas the lower SCN5A+ ratio in ERS indicates the difference in underlying electrophysiology. These findings also identify the first case of fever-induced ERS and demonstrate a critical role of Ito in JWS and a higher risk for MAE in JWS probands carrying multiple pathogenic variants in SCN5A.

Irritable bowel syndrome (IBS) is one of the most widely recognized functional bowel disorders (FBDs) with a genetic component. SCN5A gene and SCN1B loci have been identified in population-based IBS cohorts and proposed to have a mechanistic role in the pathophysiology of IBS. These same genes have been associated with Brugada syndrome (BrS). The present study examines the hypothesis that these two inherited syndromes are linked. Prevalence of FBDs over a 12 months period were compared between probands with BrS/ drug-induced type 1 Brugada pattern (DI-Type 1 BrP) (n = 148) and a control group (n = 124) matched for age, female sex, presence of arrhythmia and co-morbid conditions. SCN5A/SCN1B genes were screened in 88 patients. Prevalence of IBS was 25% in patients with BrS/DI-Type 1 BrP and 8.1% in the control group (p = 2.34 x 10(-4)). On stepwise logistic regression analysis, presence of current and/or history of migraine (OR of 2.75; 95% CI: 1.08 to 6.98; p = 0.033) was a predictor of underlying BrS/DI-Type 1 BrP among patients with FBDs. We identified 8 putative SCN5A/SCN1B variants in 7 (12.3%) patients with BrS/ DI-Type 1 BrP and 1 (3.2%) patient in control group. Five out of 8 (62.5%) patients with SCN5A/SCN1B variants had FBDs. In conclusion, IBS is a common co-morbidity in patients with BrS/DI-Type 1 BrP. Presence of current and/or history of migraine are a predictor of underlying BrS/DI-Type 1 BrP among patients with FBDs. Frequent co-existence of IBS and BrS/DI-Type 1 BrP necessitates cautious use of certain drugs among the therapeutic options for IBS that are known to exacerbate the Brugada phenotype. (C) 2021 Elsevier Inc. All rights reserved., NIH [HL47678, HL138103, HL152201]; W.W. Smith Charitable Trust; Wistar and Martha Morris Fund, \ This work was supported by grants from the NIH (HL47678, HL138103, and HL152201), W.W. Smith Charitable Trust and Wistar and Martha Morris Fund.

Background: Brugada syndrome (BrS) is a severe inherited arrhythmia syndrome which can be unmasked by fever. Methods: A clinical analysis was performed in 134 probands diagnosed with fever-induced BrS, including 59 patients who received next-generation genetic sequencing. We employed a biophysics-based computational protocol to investigate whether protein structure destabilization contributes to Nav1.5 variant-mediated fever-induced BrS. Findings: Among all cases enrolled, the symptoms at diagnosis were syncope in 26 (19.40%) and major arrhythmic events (MAE) in 16 (11.94%). SCN5A variant carriers were significantly younger than probands free of SCN5A variants. Compared with a historical cohort of non-fever BrS probands carrying SCN5A variants, carriers with fever-induced BrS were prone to MAE at younger age, and had a higher proportion of variants localizing at the interdomain linkers. Modeling result showed that most variants are destabilizing when temperature increases, suggesting that Nav1.5 structure destabilization is the cause of fever-induced BrS associated with SCN5A variants. Interpretation: In our cohort, SCN5A variant carriers with fever-induced BrS present at a younger age and harbor SCN5A variants predominantly localized to interdomain linker regions of Nav1.5. These SCN5A variants typically induce destabilization of Nav1.5 structure at higher body temperatures. Patients with SCN5A mutations present within interdomain linker regions may warrant more aggressive monitoring and management of fever. Funding Statement: The current work was supported by the National Natural Science Foundation Project of China (Grant No. 81670304); the National Institutes of Health of USA (NIH R56 - HL47678], NIH R01 [HL138103]), NIH R01 [HL152201], the W.W. Smith Charitable Trust and the Wistar and Martha Morris Fund. Declaration of Interests: The authors report no relationships that could be construed as a conflict of interest. Ethics Approval Statement: This study was approved by the Institutional Review Board of each hospital and performed in accordance with the declaration of Helsinki. All participants gave written informed consent.

Coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been associated with cardiovascular features, which may be deteriorated in patients with cancer. However, cardiac outcomes of cancer patients with COVID-19 have not been closely examined. We retrospectively assessed 1,244 patients with COVID-19 from February 1 to August 31, 2020 (140 cancer and 1,104 noncancer patients). Demographic and clinical data were obtained and compared between cancer and noncancer groups. Including the cardiac biomarkers, we also analyzed laboratory findings between these two groups. Risk factors for in-hospital mortality were identified by multivariable Cox regression models. For cancer group, 56% were in severe and critical status with more diabetes and immune deficiency, whereas the proportion was 10% for noncancer group. Patients with cancer had increased levels of leukocyte, neutrophil count, and blood urea nitrogen (BUN) (all P < 0.01), whereas lymphocyte count was significantly lower (P < 0.001). The most common solid tumor types were gastrointestinal cancer (26%), lung cancer (21%), and breast and reproductive cancer (both 19%). There is a rising for cardiac biomarkers, including pro-B-type natriuretic peptide (Pro-BNP), sensitive troponin I (cTnI), myoglobin (MYO), creatine kinase-MB (CK-MB), as well as D-Dimer in COVID-19 cancer population, especially in deceased subjects with cancer. The 30-day in-hospital mortality in cancer group was dramatically raised than that in noncancer group (12.9% vs. 4.0%, P < 0.01). In multivariable Cox regression models, fever, disease severity status, and underlying diseases were risk factors for mortality. COVID-19 patients with cancer relate to deteriorating conditions and poor cardiac outcomes accompanied by a high in-hospital mortality, which warrants more aggressive treatment. NEW & NOTEWORTHY Our study indicates that the 30-day mortality is higher in COVID-19 patients with cancer; more COVID-19 patients with cancer are in severe and critical status; age, respiratory rate, neutrophil count, AST, BUN, MYO, Pro-BNP, disease severity status, underlying diseases, and fever are risk factors for in-hospital mortality among COVID-19 cancer cases; COVID-19 patients with cancer display severely impaired myocardium, damaged heart function, and imbalanced homeostasis of coagulation; what is more, those with both cancer and CVD have more significantly increased Pro-BNP and D-Dimer level.

Introduction: Irritable bowel syndrome (IBS) is one of the most widely recognized functional bowel disorders (FBDs) with a genetic component. SCN5A gene and SCN1B loci have been identified in population-based IBS cohorts and proposed to have a mechanistic role in the pathophysiology of IBS. These same genes have been associated with Brugada syndrome (BrS). The present study examines the hypothesis that these two inherited syndromes are linked. Methods and Results: Prevalence of FBDs over a 12 months period were compared between probands with BrS/drug-induced type 1 Brugada pattern (DI-Type1 BrP) (n=148) and a control group (n=124) matched for age, female sex, presence of arrhythmia and co-morbid conditions. SCN5A/SCN1B genes were screened in 88 patients. Prevalence of IBS was 25% in patients with BrS/DI-Type1 BrP and 8.1% in the control group (p=2.34×10−4). On stepwise logistic regression analysis, presence of current and/or history of migraine (OR of 2.75; 95% CI: 1.08 to 6.98; p=0.033) was a predictor of underlying BrS/DI-Type1 BrP among patients with FBDs. We identified 8 putative SCN5A/SCN1B variants in 7 (12.3%) patients with BrS/DI-Type1 BrP and 1 (3.2%) patient in control group. Five out of 8 (62.5%) patients with SCN5A/SCN1B variants had FBDs. Conclusion: IBS is a common co-morbidity in patients with BrS/DI-Type1 BrP. Presence of current and/or history of migraine is a predictor of underlying BrS/DI-Type1 BrP among patients with FBDs. Frequent co-existence of IBS and BrS/DI-Type1 BrP necessitates cautious use of certain drugs among the therapeutic options for IBS that are known to exacerbate the Brugada phenotype.

Background Hypokalaemia-induced arrhythmia is a major cause of morbidity and mortality, affecting approximately 14% of outpatients and 20% of inpatients. Hypokalaemic inpatients have a mortality 10 times higher than their counterparts. This is due to ventricular arrhythmias initiated by early afterdepolarisations (EADs) and triggered activity. There is no antiarrhythmic drug approved for the prevention of hypokalaemia-induced ventricular arrhythmia. Recent evidence suggests that EADs can arise because of the synchronised release of Ca2+ from the sarcoplasmic reticulum, rather than the reactivation of L-type Ca2+ channels during action potential prolongation. Therefore, ryanodine receptor inhibition should prevent hypokalaemia-induced ventricular arrhythmia. Purpose To test the hypothesis that the ryanodine receptor inhibitors dantrolene and VKII-86 (a carvedilol analogue) are effective in preventing hypokalaemia-induced ventricular arrhythmia. Methods Whole heart Langendorff preparations isolated from C57BL/J6 mice were perfused with Krebs-Henseleit solution containing normal (4mM) or low (2mM) concentrations of [K+]. Surface ECG and subepicardial ventricular action potentials were simultaneously recorded. After establishing that the model reproduces EAD-mediated triggered arrhythmias in low extracellular [K+], hearts in the treatment groups were pre-treated with dantrolene or VKII-86 for 30 minutes prior to being exposed to low extracellular [K+]. The frequency of non-sustained and sustained ventricular arrhythmias occurring during a 30-minute period of exposure to low extracellular [K+] were compared between the treatment groups and controls treated with the solvent DMSO (0.1% v/v) (n=6 in each group). Results The mean number of non-sustained arrhythmias was 29.3±9.6 (Mean±SEM) in the control group, 3.2±1.2 in the dantrolene group and 0 in the VKII-86 group; p Conclusions These results provide the first demonstration of ryanodine receptor inhibition as an effective treatment for the prevention of ventricular arrhythmia in a murine model of hypokalaemia. This study is consistent with recent studies indicating that intracellular Ca2+ load is an important mechanism underlying the development of EAD-mediated triggered arrythmia. Further studies are needed to determine whether these drugs could be re-purposed as antiarrhythmics in the setting of hypokalemia. Further development of the carvedilol analogue VKII-86 should also be considered. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): The British Heart Foundation, The Lankenau Institute for Medical Research.

BackgroundCOVID-19 has been recognized as an emerging and rapidly evolving health condition. For this reason, efforts to determine changes in laboratory parameters of COVID-19 patients as biomarkers are urgent. Lipids are essential components of the human body, and their modulation has been observed implicated in some viral infections.MethodsTo evaluate the clinical diagnosis utility of the lipid profile changes in Mexican COVID-19 patients, the lipid profile of one hundred two COVID-19 positive patients from three hospitals in Culiacan, Sinaloa in northwest Mexico, was analyzed. ROC curves and binary logistic regression analysis were used as a predictive model to determine their clinical diagnostic utility.ResultsSignificant changes in the serum lipid profile of patients with COVID-19, such as low levels of cholesterol, LDL, and HDL, while high triglycerides and VLDL were observed. The same abnormalities in the lipid profile among non-critical and critical COVID-19 patients were detected. The predictive model analysis suggests that cholesterol and LDL have AUC values of 0.710 and 0.769, respectively, for COVID-19 (p= 0.0002 and p= ConclusionOur findings suggest that low cholesterol and LDL levels could be considered an acceptable predictor for COVID-19, and low levels of LDL might be a risk factor for critical COVID-19 patients.

Purpose: Stringent variant interpretation guidelines can lead to high rates of variants of uncertain significance (VUS) for genetically heterogeneous disease like long QT syndrome (LQTS) and Brugada syndrome (BrS). Quantitative and disease-specific customization of American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines can address this false negative rate. Methods: We compared rare variant frequencies from 1847 LQTS (KCNQ1/KCNH2/SCN5A) and 3335 BrS (SCN5A) cases from the International LQTS/BrS Genetics Consortia to population-specific gnomAD data and developed disease-specific criteria for ACMG/AMP evidence classes-rarity (PM2/BS1 rules) and case enrichment of individual (PS4) and domain-specific (PM1) variants. Results: Rare SCN5A variant prevalence differed between European (20.8%) and Japanese (8.9%) BrS patients (p = 5.7 x 10(-18)) and diagnosis with spontaneous (28.7%) versus induced (15.8%) Brugada type 1 electrocardiogram (ECG) (p = 1.3 x 10(-13)). Ion channel transmembrane regions and specific N-terminus (KCNH2) and C-terminus (KCNQ1/KCNH2) domains were characterized by high enrichment of case variants and >95% probability of pathogenicity. Applying the customized rules, 17.4% of European BrS and 74.8% of European LQTS cases had (likely) pathogenic variants, compared with estimated diagnostic yields (case excess over gnomAD) of 19.2%/82.1%, reducing VUS prevalence to close to background rare variant frequency. Conclusion: Large case-control data sets enable quantitative implementation of ACMG/AMP guidelines and increased sensitivity for inherited arrhythmia genetic testing., Amsterdam Cardiovascular Sciences fellowship; Dutch Heart Foundation (CVON Predict-2/Concor-genes); Netherlands Organization for Scientific ResearchNetherlands Organization for Scientific Research (NWO) [VICI 016.150.610]; Fondation LeducqLeducq Foundation, R.W. is supported by an Amsterdam Cardiovascular Sciences fellowship. C.R.B. is supported by the Dutch Heart Foundation (CVON Predict-2/Concor-genes), Netherlands Organization for Scientific Research (VICI 016.150.610), and Fondation Leducq. See Supplement for all Acknowledgements.

The mechanisms underlying atrial-selective prolongation of effective refractory period (ERP) and suppression of atrial fibrillation (AF) by NS8593 and UCL1684, small conductance calcium-activated potassium (SK) channel blockers, are poorly defined. The purpose of the study was to confirm the effectiveness of these agents to suppress AF and to probe the underlying mechanisms. Transmembrane action potentials and pseudoelectrocardiograms were recorded from canine isolated coronary-perfused canine atrial and ventricular wedge preparations. Patch clamp techniques were used to record sodium channel current (INa) in atrial and ventricular myocytes and human embryonic kidney cells. In both atria and ventricles, NS8593 (3-10 µM) and UCL1684 (0.5 µM) did not significantly alter action potential duration, suggesting little to no SK channel inhibition. Both agents caused atrial-selective: (1) prolongation of ERP secondary to development of postrepolarization refractoriness, (2) reduction of Vmax, and (3) increase of diastolic threshold of excitation (all are sodium-mediated parameters). NS8593 and UCL1684 significantly reduced INa density in human embryonic kidney cells as well as in atrial but not in ventricular myocytes at physiologically relevant holding potentials. NS8593 caused a shift of steady-state inactivation to negative potentials in atrial but not ventricular cells. NS8593 and UCL1684 prevented induction of acetylcholine-mediated AF in 6/6 and 8/8 preparations, respectively. This anti-AF effect was associated with strong rate-dependent depression of excitability. The SK channel blockers, NS8593 and UCL1684, are effective in preventing the development of AF due to potent atrial-selective inhibition of INa, causing atrial-selective prolongation of ERP secondary to induction of postrepolarization refractoriness.

Background: Although 21 causative mutations have been associated with PRKAG2 syndrome, our understanding of the syndrome remains incomplete. The aim of this project is to further investigate its unique genetic background, clinical manifestations, and underlying structural changes. Methods: We recruited 885 hypertrophic cardiomyopathy (HCM) probands and their families internationally. Targeted next-generation sequencing of sudden cardiac death (SCD) genes was performed. The role of the identified variants was assessed using histological techniques and computational modeling. Findings: Twelve PRKAG2 syndrome kindreds harboring 5 distinct variants were identified. The clinical penetrance of 25 carriers was 100.0%. Twenty-two family members died of SCD or heart failure (HF). All probands developed bradycardia (HRmin, 36.3 ± 9.8 bpm) and cardiac conduction defects, and 33% had evidence of atrial fibrillation/paroxysmal supraventricular tachycardia (PSVT) and 67% had ventricular preexcitation, respectively. Some carriers presented with apical hypertrophy, hypertension, hyperlipidemia, and renal insufficiency. Histological study revealed reduced AMPK activity and major cardiac channels in the heart tissue with K485E mutation. Computational modelling suggests that K485E disrupts the salt bridge connecting the β and γ subunits of AMPK, R302Q/P decreases the binding affinity for ATP, T400N and H401D alter the orientation of H383 and R531 residues, thus altering nucleotide binding, and N488I and L341S lead to structural instability in the Bateman domain, which disrupts the intramolecular regulation. Interpretation: Including 4 families with 3 new mutations, we describe a cohort of 12 kindreds with PRKAG2 syndrome with novel pathogenic mechanisms by computational modelling. Severe clinical cardiac phenotypes may be developed, including HF, requiring close follow-up. Keywords: Genetics, Arrhythmia, PRKAG2 syndrome, Cardiomyopathy, Heart failure, Sudden cardiac death