ABSTRACT Background Atrial Fibrillation (AF) is a common and clinically heterogeneous arrythmia. Machine learning (ML) algorithms can define data-driven disease subtypes in an unbiased fashion, but whether the AF subgroups defined in this way align with underlying mechanisms, such as high polygenic liability to AF or inflammation, and associate with clinical outcomes is unclear. Methods We identified individuals with AF in a large biobank linked to electronic health records (EHR) and genome-wide genotyping. The phenotypic architecture in the AF cohort was defined using principal component analysis of 35 expertly curated and uncorrelated clinical features. We applied an unsupervised co-clustering machine learning algorithm to the 35 features to identify distinct phenotypic AF clusters. The clinical inflammatory status of the clusters was defined using measured biomarkers (CRP, ESR, WBC, Neutrophil %, Platelet count, RDW) within 6 months of first AF mention in the EHR. Polygenic risk scores (PRS) for AF and cytokine levels were used to assess genetic liability of clusters to AF and inflammation, respectively. Clinical outcomes were collected from EHR up to the last medical contact. Results The analysis included 23,271 subjects with AF, of which 6,023 had available genome-wide genotyping. The machine learning algorithm identified 3 phenotypic clusters that were distinguished by increasing prevalence of comorbidities, particularly renal dysfunction, and coronary artery disease. Polygenic liability to AF across clusters was highest in the low comorbidity cluster. Clinically measured inflammatory biomarkers were highest in the high comorbid cluster, while there was no difference between groups in genetically predicted levels of inflammatory biomarkers. Subgroup assignment was associated with multiple clinical outcomes including mortality, stroke, bleeding, and use of cardiac implantable electronic devices after AF diagnosis. Conclusion Patient subgroups identified by unsupervised clustering were distinguished by comorbidity burden and associated with risk of clinically important outcomes. Polygenic liability to AF across clusters was greatest in the low comorbidity subgroup. Clinical inflammation, as reflected by measured biomarkers, was lowest in the subgroup with lowest comorbidities. However, there were no differences in genetically predicted levels of inflammatory biomarkers, suggesting associations between AF and inflammation is driven by acquired comorbidities rather than genetic predisposition.

To broaden our understanding of bradyarrhythmias and conduction disease, we performed common variant genome-wide association analyses in up to 1.3 million individuals and rare variant burden testing in 460,000 individuals for sinus node dysfunction (SND), distal conduction disease (DCD) and pacemaker (PM) implantation. We identified 13, 31 and 21 common variant loci for SND, DCD and PM, respectively. Four well-known loci (SCN5A/SCN10A, CCDC141, TBX20 and CAMK2D) were shared for SND and DCD, while others were more specific for SND or DCD. SND and DCD showed a moderate genetic correlation (rg = 0.63). Cardiomyocyte-expressed genes were enriched for contributions to DCD heritability. Rare-variant analyses implicated LMNA for all bradyarrhythmia phenotypes, SMAD6 and SCN5A for DCD and TTN, MYBPC3 and SCN5A for PM. These results show that variation in multiple genetic pathways (for example, ion channel function, cardiac developmental programs, sarcomeric structure and cellular homeostasis) appear critical to the development of bradyarrhythmias. Genome-wide analyses identify variants associated with sinus node dysfunction, distal conduction disease and pacemaker implantation, implicating ion channel function, cardiac developmental programs and sarcomeric structure in bradyarrhythmia susceptibility.

Obesity is a major public health crisis associated with high mortality rates. Previous genome-wide association studies (GWAS) investigating body mass index (BMI) have largely relied on imputed data from European individuals. This study leveraged whole-genome sequencing (WGS) data from 88,873 participants from the Trans-Omics for Precision Medicine (TOPMed) Program, of which 51% were of non-European population groups. We discovered 18 BMI-associated signals (P < 5 × 10-9). Notably, we identified and replicated a novel low frequency single nucleotide polymorphism (SNP) in MTMR3 that was common in individuals of African descent. Using a diverse study population, we further identified two novel secondary signals in known BMI loci and pinpointed two likely causal variants in the POC5 and DMD loci. Our work demonstrates the benefits of combining WGS and diverse cohorts in expanding current catalog of variants and genes confer risk for obesity, bringing us one step closer to personalized medicine.

Atrial fibrillation (AF) is a prevalent and morbid abnormality of the heart rhythm with a strong genetic component. Here, we meta-analyzed genome and exome sequencing data from 36 studies that included 52,416 AF cases and 277,762 controls. In burden tests of rare coding variation, we identified novel associations between AF and the genes MYBPC3, LMNA, PKP2, FAM189A2 and KDM5B. We further identified associations between AF and rare structural variants owing to deletions in CTNNA3 and duplications of GATA4. We broadly replicated our findings in independent samples from MyCode, deCODE and UK Biobank. Finally, we found that CRISPR knockout of KDM5B in stem-cell-derived atrial cardiomyocytes led to a shortening of the action potential duration and widespread transcriptomic dysregulation of genes relevant to atrial homeostasis and conduction. Our results highlight the contribution of rare coding and structural variants to AF, including genetic links between AF and cardiomyopathies, and expand our understanding of the rare variant architecture for this common arrhythmia.

Background and Aims:Genetic testing is recommended for select patients with atrial fibrillation (AF). The aims of this study were to define the results of genetic evaluation and its therapeutic impact for patients referred to a dedicated AF precision medicine clinic. Methods:Patients diagnosed with AF before age 60 were candidates for referral. In addition to standard evaluation with history, physical exam, and ECG, genetic evaluation included a 3-generation pedigree, cardiac imaging, ambulatory monitoring, and clinical genetic testing with a cardiomyopathy/arrhythmia panel. Results:264 participants were referred: the median age was 47 years (Q1, Q3: 38, 55), 77 (29%) were female, and 236 (89%) were White. Median age at AF diagnosis was 39 years (Q1, Q3: 31, 48) and median time from AF diagnosis to evaluation was 3.7 years (Q1, Q3: 0.9, 10). 242 patients (92%) underwent genetic testing, which identified a pathogenic or likely pathogenic variant in 48 (20%). The strongest predictors of positive genetic testing were history of cardiomyopathy, infranodal conduction disease, and elevated T1 or late gadolinium enhancement on cardiac MRI (all p<0.05). The strongest predictors of negative genetic testing were obstructive sleep apnea and a normal 12-lead ECG (both p<0.04). Overall, genetic testing changed clinical management in 52% of patients with positive genetic testing, highlighted by 7 new ICD placements and initiation of disease modifying therapy in 16 patients. Conclusions:Genetic testing was positive in 20% of patients with early-onset AF referred to a dedicated AF precision medicine clinic. Genetic testing results changed clinical management in approximately half of genotype-positive patients. STRUCTURED GRAPHICAL ABSTRACT:Key Question: Does genetic evaluation of patients with early-onset atrial fibrillation (AF) change their clinical management?Key Finding: Among 246 participants that completed genetic evaluation in a dedicated AF precision medicine clinic, 20% had positive genetic testing with identification of a pathogenic cardiomyopathy or channelopathy variant. These findings led to changes in clinical management in 52% of patients with positive genetic testing.Take-home Message: Genetic evaluation of patients with early-onset AF consists of detailed phenotyping and genetic testing to identify previously undiagnosed genetic disorders. This facilitates earlier diagnosis and clinical intervention.

Long QT syndrome (LQTS), an inherited cardiac arrhythmia syndrome with congenital and drug-induced presentations and known monogenic and polygenic contributions, represents a significant clinical challenge due to its complex genetic underpinning and propensity for fatal arrhythmias. In this study, we generated induced pluripotent stem cells (iPSCs) reprogrammed from peripheral blood mononuclear cells (PBMCs) of six patients with extreme polygenic scores for short and long corrected QT intervals. This patient-specific approach will enable us to better understand variable expressivity and penetrance of LQTS, using rigorously validated iPSC lines serve as a vital resource for elucidating the molecular mechanisms underlying LQTS.

BACKGROUND:Inflammation is a common mechanism for atrial fibrillation (AF). 2-Hydroxybenzylamine (2-HOBA) is a novel therapeutic that scavenges isolevuglandins-a downstream mediator of inflammation and oxidative stress. 2-HOBA is safe and reduces AF in mice, prompting a first-in-human pilot clinical trial. METHODS:Participants were enrolled and randomized 1:1 to placebo or 2-HOBA (750 mg p.o. TID) 3 days before a planned AF ablation. Participants were monitored for 28 days after their ablation for recurrence of AF as detected by smartwatch single-lead ECG recordings. Blood was collected at the time of ablation for measurement of isolevuglandin levels. The study drug was stopped at 28 days. A 12-month extended follow-up period was used to monitor for any residual effect of the study drug on AF recurrence. RESULTS:2-HOBA increased the risk of AF recurrence in the postablation population (odds ratio, 3.65 [95% CI, 1.31-10.16]; P=0.013) after prespecified adjustment for potential confounders. This increased risk of recurrence remained despite post hoc adjustment for other clinical risk factors. There was no difference in isolevuglandin levels between the 2-HOBA and placebo groups. After the study drug was stopped, there was no difference in AF recurrence between the 2-HOBA and placebo groups during the 12-month extended follow-up. CONCLUSIONS:2-HOBA was associated with a higher risk of AF recurrence when tested early after AF ablation. This result was unexpected based on preclinical data, but paradoxical associations with AF have been previously reported for other drugs that target inflammation and oxidative stress pathways, such as omega-3 fatty acids. The mechanisms for AF immediately following ablation may be different from AF that occurs under other conditions, and the generalizability of these results to all forms of AF remains unknown.

Background: Cardiac sympathetic denervation (CSD) is a well-established procedure to prevent ventricular arrhythmias in genetic and acquired arrhythmia syndromes. It is unknown whether initial bilateral (B) CSD or left (L) CSD, followed by right (R) CSD for breakthrough events is the better strategy. Aims: We compared the antiarrhythmic efficacy and complications of primary B vs L CSD at a single center where both are performed routinely. Methods: Patients who underwent CSD were retrospectively identified. At our center L CSD is performed in children while B CSD is performed in adults by operator preference. Demographic data, procedural indications, complications, and arrhythmia events (arrhythmic syncope, sudden cardiac arrest, appropriate shock) were collected. Arrhythmia events (AE) were compared before and after CSD in those with arrhythmia indications. Complications were compared in all subjects and in the subset with arrhythmia indications. Results: Between 2011 and 2023, 65 patients underwent 68 CSD procedures (39 B, 26 L, 3 R after initial L). As expected, BCSD patients were older [median 32 (IQR 21-48) years vs. 16 (6-38) years; P=0.002]. Overall complication rates were similar [BCSD 17/39 (44%) vs 12/29 (41%), P=0.85]; most were transient/minor. Complications that required intervention were rare (n=5) and only observed after BCSD. Forty CSD were for an arrythmia indication (18 B, 21 L, 1 R). AEs were reduced from a median of 3 (1-4) before CSD to 0 (0-1) after CSD (p<0.001). The reduction was similar for BCSD [3.5 (2-5) before vs 0 (0-0.25) after (p<0.001)] and L/R CSD [2 (1-4) before vs 0 (0-1) after (p=0.002)]. Only 1 LCSD had subsequent RCSD for an arrhythmia indication 4 years later due to breakthrough AEs: a severe long QT syndrome patient who ultimately required heart transplant. Complications that required intervention after CSD for an arrhythmia indication were seen in 4/18 BCSD and 0/22 L/R CSD (P=0.03). Conclusions: BCSD and LCSD are both highly effective in reducing arrhythmia events. Complication rates may be less frequent in unilateral CSD, although the observed difference may be due age differences in the two groups.

Background:KCNQ1 loss of function variants are thought to cause type 1 long QT syndrome by reducing I Ks. However, we have recently reported that pharmacologic block of I Ks in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) produced minimal increases in action potential duration at 90% repolarization (APD90), while genetic loss of KCNQ1 markedly prolonged APD90. We sought here to define mechanisms underlying APD prolongation by genetic loss of KCNQ1. Methods:We studied iPSC-CMs from population controls, an isogenic KCNQ1 knock out (KO) line created by a homozygous edit for the R518X loss of function variant, and 2 unrelated patients with the Jervell and Lange-Nielsen syndrome (JLN) due to compound heterozygosity for loss of function KCNQ1 variants. Results:In both JLN and the KCNQ1-KO lines, I Ks was absent, APD90 was markedly prolonged, and L-type Ca channel (LTCC) current (I Ca-L) was significantly increased, 2-3-fold, compared to the control cells with no change in kinetics or gating. RNA-sequencing identified 298 and 584 genes that were up- and down-regulated, respectively, by KCNQ1-KO compared to the isogenic control cells. Gene ontology analysis identified down-regulation of 6 Ca2+ channel negative regulatory genes (p=0.0002, FDR=0.02), and in knockdown experiments in wild-type iPSC-CMs, three of these, CBARP, FKBP1B, and RRAD, increased I Ca-L, and RRAD increased APD90. A therapeutic low concentration (1 μM) of the Ca channel antagonist diltiazem significantly shortened APD90 in the two JLN cell lines and in KCNQ1-KO cells. A single low dose of intravenous diltiazem in one of the JLN patients shortened QTc. Conclusions:These data further support the concept that delayed repolarization in JLN cannot be explained solely by loss of I Ks. Our findings demonstrate that KCNQ1 mutations lead to down-regulation of Ca2+ channel inhibitory genes, with resultant increased I Ca-L that underlies delayed repolarization in JLN. We further propose that diltiazem can be repurposed for treatment of patients with JLN.

With the demonstration that AF is highly hereditable and strongly associated with over 100 genetic loci, one step towards personalized treatment of AF is the potential use of genetic testing to predict response to therapy. Although various clinical models have been developed to predict recurrence, none have shown a consistent ability to predict treatment outcomes. This highlights a need for additional patient information to increase predictive value. Here, we review the use of genetic data for prediction of AF recurrence after interventions such as ablation, cardioversion, or drug therapy. We explore the use of other downstream predictors, such as mRNA and protein, as other possible predictive tools. Finally, we assess how this genetic data can further our mechanistc understanding of AF pathogenesis and recurrence.

BACKGROUND:Radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in arrhythmogenic right ventricular cardiomyopathy is safe and reduces ventricular arrhythmia burden. Previous studies included adult patients, and data on pediatric patients are scarce. The objective of our study was to report on the safety and efficacy of RFCA in pediatric arrhythmogenic right ventricular cardiomyopathy. METHODS:Fifteen patients who fulfilled the 2010 arrhythmogenic right ventricular cardiomyopathy task force criteria, clinically presented before the age of 18, and underwent VT RFCA procedures at ≤21 years old were included. Baseline characteristics, genotypic and phenotypic data, and ablation outcomes were collected. RESULTS:The mean age at symptom onset was 15.5±1.6 years, and at the index procedure was 18.1±2 years, with 73% of the patients being male. Pathogenic mutation in desmosomal genes was detected in 87%. First presentation symptoms included palpitations (33%), syncope (27%), sustained VT (27%), and sudden cardiac arrest (13%). ECG repolarization abnormalities were present in 93% and 40% were reported to be athletes. In the index RFCA procedure, sustained monomorphic VT was induced in 60%. Electroanatomic mapping showed 100% basal RV epicardial substrate and 54% endocardial low voltage/scar. Repeat VT ablation was required in 80% over a mean follow-up of 16.4 months. The median number of procedures was 2 (interquartile range, 2-4), with sustained VT-free survival of 73% over a mean follow-up duration of 21.4 months. No acute periprocedural complications occurred. Bilateral cardiac sympathetic denervation due to recurrent ventricular arrhythmia was performed in 27%. Eventually, 2 patients (13%) developed advanced heart failure and underwent heart transplantation. CONCLUSIONS:Pediatric arrhythmogenic right ventricular cardiomyopathy RFCA is safe, but early recurrences are common, requiring repeat ablations and sometimes bilateral cardiac sympathetic denervation. The substrate is mostly epicardial with preserved endocardial voltage. VT free survival is 73% after multiple procedures. Progressive heart failure requiring transplantation occurred in 13% within 2 decades of initial presentation.

Atrial fibrillation (AF) is the most common heart rhythm abnormality and is a leading cause of heart failure and stroke. This large-scale meta-analysis of genome-wide association studies increased the power to detect single-nucleotide variant associations and found more than 350 AF-associated genetic loci. We identified candidate genes related to muscle contractility, cardiac muscle development and cell-cell communication at 139 loci. Furthermore, we assayed chromatin accessibility using assay for transposase-accessible chromatin with sequencing and histone H3 lysine 4 trimethylation in stem cell-derived atrial cardiomyocytes. We observed a marked increase in chromatin accessibility for our sentinel variants and prioritized genes in atrial cardiomyocytes. Finally, a polygenic risk score (PRS) based on our updated effect estimates improved AF risk prediction compared to the CHARGE-AF clinical risk score and a previously reported PRS for AF. The doubling of known risk loci will facilitate a greater understanding of the pathways underlying AF.

Importance Filamin C truncating variants (FLNCtv) are a rare cause of cardiomyopathy with heterogeneous phenotypic presentations. Despite a high incidence of life-threatening ventricular arrhythmias and sudden cardiac death (SCD), reliable risk predictors to stratify carriers of FLNCtv are lacking. Objective To determine factors predictive of SCD/major ventricular arrhythmias (MVA) in carriers of FLNCtv. Design, Setting, and Participants This was an international, multicenter, retrospective cohort study conducted from February 2023 to June 2024. The Filamin C Registry Consortium included 19 referral centers for genetic cardiomyopathies worldwide. Participants included carriers of pathogenic or likely pathogenic FLNCtv. Phenotype negative was defined as the absence of any pathological findings detected by 12-lead electrocardiogram (ECG), Holter ECG monitoring, echocardiography, or cardiac magnetic resonance. Exposures Composite of SCD and MVA in carriers of FLNCtv. Main Outcomes and Measures The primary outcome was a composite of SCD and MVA, the last including aborted SCD, sustained ventricular tachycardia, and appropriate implantable cardioverter-defibrillator (ICD) interventions. Results Among 308 individuals (median [IQR] age, 45 [33-56] years; 160 male [52%]) with FLNCtv, 112 (36%) were probands, and 72 (23%) were phenotype negative. Median (IQR) left ventricular ejection fraction (LVEF) was 51% (38%-59%); 89 participants (34%) had LVEF less than 45%, and 50 (20%) had right ventricular dysfunction. During a median (IQR) follow-up of 34 (8-63) months, 57 individuals (19%) experienced SCD/MVA, with an annual incidence rate of 4 cases per 100 person-years (95% CI, 3-6). Incidence rates were higher in probands vs nonprobands and in phenotype-positive vs phenotype-negative individuals. A predictive model estimating SCD/MVA risk was derived from multivariable analysis, which included older age, male sex, previous syncope, nonsustained ventricular tachycardia, and LVEF with a time-dependent area under the curve (AUC) ranging between 0.76 (95% CI, 0.67-0.86) at 12 months and 0.78 (95% CI, 0.70-0.86) at 72 months. Notably, the association of LVEF with the SCD/MVA risk was not linear, showing significant lower risk for values of LVEF greater than 58%, and no increase for values less than 58%. Internal validation with bootstrapping confirmed good accuracy and calibration of the model. Results were consistent in subgroups analysis (ie, phenotype-positive carriers and phenotype-positive carriers without MVA at onset). Conclusions and Relevance Results suggest that the risk of SCD/MVA in phenotype-positive carriers of FLNCtv was high. A 5-variable predictive model derived from this cohort allows risk estimation and could support clinicians in the shared decision for prophylactic ICD implantation. External cohort validation is warranted.

Background: Genetic testing is now recommended for select patients with early-onset atrial fibrillation (AF). Hemochromatosis is an autosomal recessive syndrome that occurs in patients who carry two pathogenic or likely-pathogenic (P/LP) variants in HFE. HFE is included on some genetic testing panels used for patients with AF. Hemochromatosis causes cardiomyopathy due to iron overload in the ventricle; however, it is unknown whether AF can be an early manifestation that is identified by genetic testing. Methods: A total of 347 patients were referred to a dedicated AF precision medicine clinic. The clinical diagnostic evaluation included an H&P, 12-lead ECG, ambulatory ECG monitoring, and cardiac imaging (cardiac MRI and/or TTE). Genetic testing was performed using CLIA-approved laboratories: Labcorp/Invitae, GeneDx, or Vanderbilt University Medical Center. HFE was included on the cardiomyopathy panel used by 2 of the 3 laboratories. Results: HFE was tested in 165 participants (median age 46 years [IQR 35-55], 115 [70%] male, 149 [90%] White). Six participants (4%) had two pathogenic variants in HFE. All of them were C282Y/H63D compound heterozygotes. Forty-one participants (25%) were heterozygous carriers of one pathogenic HFE variant. Among the 6 participants with 2 pathogenic HFE variants, the median ferritin level was 346 mcg/L [IQR 262, 496] (normal <300 mcg/L males, <200 mcg/L females). Three participants (50%) met laboratory criteria for iron overload. One individual had isolated ferritin elevation with normal transferrin saturation. All 6 underwent cardiac MRI as part of the genetic evaluation for early onset AF, and there was no evidence of cardiac siderosis based on cardiac T1 mapping, median 990 ms [IQR 968-1024] (normal 960-1030 ms). Dedicated sequences to evaluate for iron overload demonstrated short hepatic T2* in one individual, indicating presence of hepatic iron overload (9 ms, normal >11.4 ms; liver iron concentration 3.4 mg/g, normal <2 mg/g). Three out of 6 participants were referred for a hematology evaluation and 2 out of 6 were started on therapeutic phlebotomy. Conclusion: Genetic testing can identify patients with early-onset AF who are genetically susceptible to hemochromatosis, have evidence of iron overload, and receive early intervention with therapeutic phlebotomy. These results suggest HFE should be sequenced as part of genetic testing for early-onset AF, but larger sample sizes are needed to confirm these results.

Despite clinical need, no new drugs for treating ventricular tachycardia (VT) have emerged for over 20 years. In structural heart disease, posttranslational modifications render intracellular ryanodine receptor-2 (RyR2) calcium release channels leaky, which increases VT risk. Treatment with dantrolene, an RyR2 inhibitor, prevents VT in animal models. Here, we test Dantrolene in a randomized, double-blinded, placebo-controlled clinical trial of 51 patients with structural heart disease undergoing catheter ablation for ventricular arrhythmias. Cardiac electrophysiologic parameters, hemodynamics and VT inducibility were assessed at baseline and after IV administration of dantrolene (29 patients) or placebo (22 patients). Approximately half of study participants were inducible at baseline. Dantrolene reduced inducible VT by 66% whereas placebo had no effect (odds ratio 0.23, 95% CI 0.06-0.90, P=0.034). Dantrolene had no significant effects on conduction velocity, effective refractory periods, heart rate, ECG intervals, blood pressure, or cardiac function. We conclude that Dantrolene reduced VT inducibility in high-risk patients with a favorable safety profile. These findings support the safety and efficacy of targeting RyR2 for arrhythmia prevention in humans. Clinicaltrials.gov NCT04134845 .

Background TTN encodes a sarcomeric protein called titin. Pathogenic rare variants in TTN are the most common finding in patients with atrial fibrillation (AF) and positive genetic testing. Objectives This study sought to define the characteristics and outcomes in patients with AF and pathogenic TTN variants compared with genotype-negative patients with AF. Methods Patients who presented initially with AF were enrolled in an AF registry. Retrospectively they underwent research sequencing for cardiomyopathy and arrhythmia genes. TTN(+) AF cases were defined as participants with pathogenic or likely pathogenic (P/LP) rare variants located in exons with high cardiac expression. They were matched 1:2 with control subjects with no P/LP variants. Phenotyping used retrospective manual chart review. Results Among 2794 participants; 57 (2.0%) TTN(+) AF cases were identified and matched with 114 control subjects. Low QRS complex voltage was present more often in TTN(+) AF cases (18% vs 5%; P < 0.01), with no difference in PR, QRS interval, or QTc. More TTN(+) AF cases had persistent AF at enrollment (44% vs 30%; P = 0.028) and had undergone multiple cardioversions (61% vs. 37%; P < 0.01). By end of follow-up (median 8.3 years; Q1, Q3: 4.5, 13.7 years), 11% of TTN(+) AF cases developed sustained ventricular tachycardia/ventricular fibrillation, 44% left ventricular (LV) systolic dysfunction (LV ejection fraction <50%), and 47% met a combined endpoint of sustained ventricular tachycardia/ventricular fibrillation or LV systolic dysfunction. Conclusions TTN(+) AF patients undergo more cardioversions and have more persistent forms of AF. Approximately 50% develop LV systolic dysfunction and/or malignant ventricular arrhythmias. These results highlight the need for diagnostic evaluation and management in TTN(+) patients beyond the usual care for AF.

Background Sudden unexpected death in children is a tragic event. Understanding the genetics of sudden death in the young (SDY) enables family counseling and cascade screening. The objective of this study was to characterize genetic variation in an SDY cohort using whole genome sequencing. Methods The SDY Case Registry is a National Institutes of Health/Centers for Disease Control and Prevention surveillance effort to discern the prevalence, causes, and risk factors for SDY. The SDY Case Registry prospectively collected clinical data and DNA biospecimens from SDY cases < 20 years of age. SDY cases were collected from medical examiner and coroner offices spanning 13 US jurisdictions from 2015 to 2019. The cohort included 211 children (median age 0.33 year; range 0–20 years), determined to have died suddenly and unexpectedly and from whom DNA biospecimens for DNA extractions and next-of-kin consent were ascertained. A control cohort consisted of 211 randomly sampled, sex- and ancestry-matched individuals from the 1000 Genomes Project. Genetic variation was evaluated in epilepsy, cardiomyopathy, and arrhythmia genes in the SDY and control cohorts. American College of Medical Genetics/Genomics guidelines were used to classify variants as pathogenic or likely pathogenic. Additionally, pathogenic and likely pathogenic genetic variation was identified using a Bayesian-based artificial intelligence (AI) tool. Results The SDY cohort was 43% European, 29% African, 3% Asian, 16% Hispanic, and 9% with mixed ancestries and 39% female. Six percent of the cohort was found to harbor a pathogenic or likely pathogenic genetic variant in an epilepsy, cardiomyopathy, or arrhythmia gene. The genomes of SDY cases, but not controls, were enriched for rare, potentially damaging variants in epilepsy, cardiomyopathy, and arrhythmia-related genes. A greater number of rare epilepsy genetic variants correlated with younger age at death. Conclusions While damaging cardiomyopathy and arrhythmia genes are recognized contributors to SDY, we also observed an enrichment in epilepsy-related genes in the SDY cohort and a correlation between rare epilepsy variation and younger age at death. These findings emphasize the importance of considering epilepsy genes when evaluating SDY.

BACKGROUND:Atrial fibrillation (AF) recurrence is common after catheter ablation. Pulmonary vein (PV) isolation is the cornerstone of AF ablation, but PV remodeling has been associated with the risk of AF recurrence. We aimed to evaluate whether artificial intelligence-based morphological features of primary and secondary PV branches on computed tomography images are associated with AF recurrence post-ablation. METHODS:Two artificial intelligence models were trained for the segmentation of computed tomography images, enabling the isolation of PV branches. Patients from Cleveland Clinic (N=135) and Vanderbilt University (N=594) were combined and divided into 2 sets for training and cross-validation (D1, n=218) and internal testing (D2, n=511). An independent validation set (D3, N=80) was obtained from University Hospitals of Cleveland. We extracted 48 fractal-based and 12 shape-based radiomic features from primary and secondary PV branches of patients with AF recurrence (AF+) and without recurrence after catheter ablation of AF (AF-). To predict AFrecurrence, 3 Gradient Boosting classification models based on significant features from primary (Mp), secondary (Ms), and combined (Mc) PV branches were built. RESULTS:Features relating to primary PVs were found to be associated with AF recurrence. The Mp classifier achieved area under the curve values of 0.73, 0.71, and 0.70 across the 3 datasets. AF+ cases exhibited greater surface complexity in their primary PV area, as evidenced by higher fractal dimension values compared with AF- cases. The Ms classifier results revealed a weaker association with AF+, suggesting higher relevance to AF recurrence post-ablation from primary PV branch morphology. CONCLUSIONS:This largest multi-institutional study to date revealed associations between artificial intelligence-extracted morphological features of the primary PV branches with AF recurrence in 809 patients from 3 sites. Future work will focus on enhancing the predictive ability of the classifier by integrating clinical, structural, and morphological features, including left atrial appendage and left atrium-related characteristics.

BACKGROUND:Substantial data support a heritable basis for supraventricular tachycardias, but the genetic determinants and molecular mechanisms of these arrhythmias are poorly understood. We sought to identify genetic loci associated with atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular accessory pathways or atrioventricular reciprocating tachycardia (AVAPs/AVRT).METHODS:We performed multiancestry meta-analyses of genome-wide association studies to identify genetic loci for AVNRT (4 studies) and AVAP/AVRT (7 studies). We assessed evidence supporting the potential causal effects of candidate genes by analyzing relations between associated variants and cardiac gene expression, performing transcriptome-wide analyses, and examining prior genome-wide association studies.RESULTS:Analyses comprised 2384 AVNRT cases and 106 489 referents, and 2811 AVAP/AVRT cases and 1,483 093 referents. We identified 2 significant loci for AVNRT, which implicate NKX2-5 and TTN as disease susceptibility genes. A transcriptome-wide association analysis supported an association between reduced predicted cardiac expression of NKX2-5 and AVNRT. We identified 3 significant loci for AVAP/AVRT, which implicate SCN5A, SCN10A, and TTN/CCDC141. Variant associations at several loci have been previously reported for cardiac phenotypes, including atrial fibrillation, stroke, Brugada syndrome, and electrocardiographic intervals.CONCLUSIONS:Our findings highlight gene regions associated with ion channel function (AVAP/AVRT), as well as cardiac development and the sarcomere (AVAP/AVRT and AVNRT) as important potential effectors of supraventricular tachycardia susceptibility.

BACKGROUND: Brugada syndrome is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging, and approximate to 79% of SCN5A missense variants in ClinVar are currently classified as variants of uncertain significance. Automated patch clamp technology enables high-throughput functional studies of ion channel variants and can provide evidence for variant reclassification. METHODS: An in vitro SCN5A-Brugada syndrome automated patch clamp assay was independently performed at Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute. The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. Odds of pathogenicity values were derived from the experimental results according to ClinGen Sequence Variant Interpretation recommendations. The calibrated assay was then used to study SCN5A variants of uncertain significance observed in 4 families with Brugada syndrome and other arrhythmia phenotypes associated with SCN5A loss-of-function. RESULTS: Variant channel parameters generated independently at the 2 research sites showed strong correlations, including peak INa density (R2=0.86). The assay accurately distinguished benign controls (24/25 concordant variants) from pathogenic controls (23/24 concordant variants). Odds of pathogenicity values were 0.042 for normal function and 24.0 for abnormal function, corresponding to strong evidence for both American College of Medical Genetics and Genomics/Association for Molecular Pathology benign and pathogenic functional criteria (BS3 and PS3, respectively). Application of the assay to 4 clinical SCN5A variants of uncertain significance revealed loss-of-function for 3/4 variants, enabling reclassification to likely pathogenic. CONCLUSIONS: This validated high-throughput assay provides clinical-grade functional evidence to aid the classification of current and future SCN5A-Brugada syndrome variants of uncertain significance.