Brugada Syndrome Cases Research Articles

Brugada syndrome in a patient with AKAP9 mutation: Case report and review of the literature

Brugada syndrome (BrS) is a rare autosomal dominant inherited channel disorder characterized by a specific electrocardiographic pattern of right precordial ST-segment elevation. Clinically, patients may experience polymorphic ventricular tachycardia and ventricular fibrillation, leading to recurrent syncope and sudden cardiac death (SCD) in the absence of structural cardiomyopathy. The A-kinase anchor protein 9 (AKAP9) gene, located on chromosome 7, encodes the AKAP9 protein, which plays a crucial role in regulating the phosphorylation of slowly activating delayed rectifier potassium channels (IKs). Here, we present a rare case of BrS associated with an insertion mutation in AKAP9, resulting in a frameshift mutation.

The role of GPD1L, a sodium channel interacting gene, in the pathogenesis of Brugada Syndrome.

Brugada Syndrome (BrS) is an inherited arrhythmia syndrome in which mutations in the cardiac sodium channel SCN5A (NaV1.5) account for approximately 20% of cases. Mutations in sodium channel-modifying genes may account for additional BrS cases, though BrS may be polygenic given common SNPs associated with BrS have been identified. Recent analysis, however, has suggested that SCN5A should be regarded as the sole monogenic cause of BrS. We sought to re-assess the genetic underpinnings of BrS in a large mutligenerational family with a putative mutation in GPD1L that affects surface membrane expression of NaV1.5 in vitro. Fine linkage mapping was performed in the family using the Illumina Global Screening Array. Whole exome sequencing of the proband was performed to identify rare variants and mutations, and Sanger sequencing was used to assay previously-reported risk single nucleotide polymorphsims (SNPs) for BrS. Linkage analysis decreased the size of the previously-reported microsatellite linkage region to approximately 3 Mb. GPD1L-A280V was the only coding non-synonymous variation present at less than 1% allele frequency in the proband within the linkage region. No rare non-synonymous variants were present outside the linkage area in affected individuals in genes associated with BrS. Risk SNPs known to predispose to BrS were overrepresented in affected members of the family. Together, our data suggest GPD1L-A280V remains the most likely cause of BrS in this large multigenerational family. While care should be taken in interpreting variant pathogenicity given the genetic uncertainty of BrS, our data support inclusion of other putative BrS genes in clinical genetic panels.

Study of the cardiac sodium channel in a mouse model of Scn5a haploinsufficiency towards a novel approach of therapy

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Sorbonne Université doctoral scolarship INSERM Introduction Brugada syndrome (BrS) is an inherited cardiac arrhythmia that greatly increases the risk of sudden death as a result of ventricular fibrillation. Approximately 20% of BrS cases can be attributed to a mutation in SCN5A, the gene encoding the alpha-subunit Nav1.5 of the cardiac sodium-channel, which carries the sodium current INa. These mutations typically lead to loss-of-function of Nav1.5, resulting in a decrease in INa and most of them (»70 %) are responsible for haploinsufficiency. In the Scn5a+/- mouse model, a sodium-channel dysfunction phenotype is observed, characterized by conduction abnormalities (PR and QRS interval prolongation), a 50% reduction in INa, and an increased susceptibility to arrhythmias. Aim The aim of this study was to assess the impact of the overexpression of a Nav1.5-peptide, which has been found to enhance INa, in Scn5a+/- mice, as a novel approach of therapy. Methods We used AAV9-systemic injection to overexpress the Nav1.5-peptide into the heart of Scn5a+/- mice to gauge their susceptibility to arrhythmias induced by intracardiac pacing. We also examined the Nav1.5-peptide effects on endogenous Nav1.5 expression through molecular biology and biochemistry analyses. Results The duration of PR and QRS intervals in the hearts of Scn5a+/- mice was restored to normal by overexpression of the Nav1.5-peptide (PR interval = 46.3 ± 0.9 ms, n=22 in Scn5a+/- mice vs 40.4 ± 0.8 ms, n= 23 in WT mice, P<0.0001 and 42.6 ± 0.9 ms, n=11 in Scn5a+/- +Nav1.5-peptide, P<0.05; QRS interval = 15.2 ± 0.4, n=22 ms in Scn5a+/- mice vs 13.2 ± 0.4 ms, n=23 in WT mice, P<0.01 and 13.6 ± 0.4 ms, n=14 in Scn5a+/- +Nav1.5-peptide, P<0.05). Additionally, overexpression of the Nav1.5-peptide seemed to protect Scn5a+/- mice from induced arrhythmic events caused by programmed-ventricular stimulation (total premature beats = 1.3 ± 0.4 in Scn5a+/- mice, n = 13 vs 0.2 ± 0.2, n = 6 in injected Scn5a+/- mice, NS and 0.2 ± 0.2, n = 12 in WT mice, P< 0.05). There were no significant differences in total Nav1.5 expression between injected and non-injected mice as shown by RT-qPCR and Western-blots, but the expression of Nav1.5 at the plasma membrane appeared to be restored by overexpression of the Nav1.5-peptide (Nav1.5/N-cadherin ratio = 0.50 ± 0.08, n = 11 in Scn5a+/- mice vs 1 ± 0.15, n= 11 in WT mice, P< 0.05 and 0.94 ± 0.13, n = 11 in injected Scn5a+/- mice, P< 0.05). Conclusion Gene therapy with Nav1.5-peptide can attenuate both conduction defects and increased arrhythmia inducibility observed in Scn5a+/- mice. Although additional studies will be needed to confirm and explore further our results, this could be promising to treat patients with « sodium-channel dysfunction » such as BrS.

Abstract 17335: Novel Functional Genomic Studies in Scn1bb Variant Associated With Brugada Syndrome and the Ameliorative Effect of Acacetin

Background: Brugada syndrome (BrS) is a channelopathy associated with the development of life-threatening ventricular tachycardia and fibrillation (VT/VF). At present, pharmacological approaches to therapy are very limited. Objective: To evaluate the effect of an SCN1Bb variant and the effects of acacetin in experimental models of BrS. Methods: We evaluated the effect of acacetin in: 1) HEK293 cells expressing Kv4.3+ KChIP2 and Nav1.5+ SCN1B using patch clamp techniques (22 O C), 2) canine ventricular epicardial myocytes 3) coronary-perfused canine right (RV) preparations and 4) Langendorff-perfused canine whole-heart models of BrS in which the sodium channel blocker ajmaline or the calcium channel blocker verapamil, together with the transient outward current agonist NS5806 were used to provoke the arrhythmic phenotype. Results: Co-expression of SCN5A -WT+ KCND3-WT with KChIP2 + SCN1Bb -R214Q (variant associated with 3 cases of BrS and 1 case of sudden infant death (SIDS)), resulted in a 210% increase in total charge of the transient outward potassium current (I to ) as well as a 56.5% reduction in sodium channel current (I Na ) when compared to SCN1Bb-WT . In the absence of the mutation, acacetin inhibited I to with an IC 50 of 7.2±1.0 μM (n=3) in HEK cells, similar to the value obtained in native epicardial myocytes (6 μM). In the presence of the SCB1Bb mutant, IC 50 was dramatically reduced to 2.6±1 μM (n=5, p<0.05) Mean ±SEM. In the wedge and whole-heart models of BrS, acacetin dose-dependently reduced the epicardial action potential notch recorded from the RV or RVOT. Acacetin (5-10 μM) totally suppressed the electrocardiographic and arrhythmic manifestation of BrS, regardless of the pharmacologic model used to induce the arrhythmic phenotype. All repolarization defects were reversed, resulting in marked diminution of J waves leading to total suppression of VT/VF. Conclusions: Our findings demonstrate the ability of an SCN1Bb variant to dramatically shift the balance of current in the early phases of the RV epicardial action potential by reducing I Na as well as augmenting I to , thus predisposing to the development of the BrS phenotype. Our observations also hold promise for acacetin as a safe and effective pharmacologic treatment for BrS and some cases of SIDS.

Future direction of substrate-based catheter ablation in Brugada syndrome and other inherited primary arrhythmia syndromes: Systematic review and meta-analysis.

Inherited Primary Arrhythmias Syndromes (IPAS), especially Brugada syndrome (BrS), have been associated with arrhythmogenic substrates that can be targeted through ablation. This meta-analysis evaluated the outcomes of catheter ablation (CA) in different types of IPAS based on procedural guidance and location. A systematic search was conducted across multiple databases to identify studies reporting on ventricular arrhythmia (VA) events before and after CA in IPAS, including BrS, Long-QT syndrome (LQTS), Early repolarization syndrome (ERS), and Idiopathic ventricular fibrillation (IVF). The primary outcomes were VA recurrence and VA burden, evaluated through conditional subgroup analysis. Procedural data were collected as secondary outcomes. A total of 21 studies involving 584 IPAS patients who underwent CA were included. Following a mean follow-up duration of 33.5 months, substrate-based ablation demonstrated efficacy in reducing VA recurrence across all types of IPAS [RR 0.23; 95% CI (0.13-0.39); p < .001; I 2 = 74%]. However, activation guidance ablation was found to be effective only in IVF cases. Although recurrences still occurred, CA was successful in reducing VA burden [MD -4.70; 95% CI (-6.11-(-3.29); p < .001; I 2 = 74%]. The mean size of arrhythmogenic substrate was 15.70 cm2 [95% CI (12.34-19.99 cm2)], predominantly distributed in the epicardial right ventricular outflow tract (RVOT) in BrS cases and LQTS [Proportion 0.99; 95% CI (0.96-1.00) and Proportion 0.82; 95% CI ( 0.59-1.00), respectively]. Substrate-based CA has demonstrated effective prevention of VA and reduction in VA burden in IPAS cases.

Abstract P3131: SIRTUIN5 Modulates Na + /Ca 2+ Handling Through Oxidative Stress Dependent Mechanism In Mouse Heart

Mutations in cardiac sodium channel Na V 1.5 (encoded by SCN5A) can cause inherited or acquired arrhythmias, including ~20% of cases of Brugada Syndrome (BrS) and inherited conduction disease. The peak Na V 1.5 current (I Na, Peak ) and the late current (I Na, Late ) govern the fast upstroke and plateau of the cardiac action potential, respectively. Ca 2+ ions impact excitation-contraction coupling, and imbalance in Na + /Ca 2+ homeostasis can cause electrical disturbance. BrS is characterized by a right bundle branch block pattern on EKG, arrhythmias, and sudden cardiac death. Recently, potential mutations in SIRT5, including P114T-SIRT5, were identified in small families with BrS. SIRT5 is a member of the Sirtuin family, acts as NAD + -dependent deACYLase.We explored the potential role of SIRT5 in BrS using heterologous expression systems and homozygous P114T-SIRT5 knock-in (P114T-KI) mice. SIRT5 co-immunoprecipitates with Na V 1.5 in HEK293 cells. Live-cell staining using DCFDA or mitoSOX showed that P114T-KI hearts had increased basal reactive oxygen species (ROS) and were more sensitive to oxidative stress induced by H 2 O 2 than wild-type littermates. P114T mice displayed Ca 2+ -mishandling as measured by Ca 2+ imaging in perfused hearts, increased I Na, Late , prolonged QTc, and arrhythmias. Notably, treatment with mitochondrial ROS scavenger mitotempo mitigated the aberrant Ca 2+ handling and arrhythmia in P114T mice.Together, these suggest that P114T-SIRT5 causes Na + /Ca 2+ mishandling-induced arrhythmias in ROS-dependent manner, highlighting potential mechanisms underlying BrS. They pave the way for using SIRT5 or its activators as novel anti-arrhythmic therapies.

Unmasking a Silent Killer and Understanding Sudden Cardiac Death in Brugada Syndrome: A Traditional Review.

Brugada syndrome (BrS) is an intricate and heterogeneous genetic disorder that engenders a formidable risk of life-threatening ventricular arrhythmias (VAs). While initially regarded as an electrophysiological aberration, emergent studies have illuminated the presence of underlying structural anomalies in select BrS cases. Although mutations in the SCN5A gene encoding the α-subunit of the cardiac sodium channel were originally identified as a primary causative factor; they account for only a fraction of the syndrome's multifaceted complexity pointing at genetic heterogeneity as a contributing factor. Remarkably, BrS has been linked to a higher incidence of fatal arrhythmic incidents and sudden cardiac death (SCD) with about 4% of SCD cases thought to be caused by BrS. Patients who spontaneously exhibit type one Brugada ECGs are more likely to experience cardiac events,emphasizing the importance of early risk stratification. To aid in risk stratification, the Shanghai score; a multifactorial risk stratification scoring system that incorporates ECG, clinical history, family history, and genetic test results; is utilized to identify those most susceptible to SCD. Beyond single ECGs, evaluation of arrhythmic findings from 24-hour Holter monitoring, ECG variables, electrophysiologic study (EPS) status in the temporal domain, and EPS data collected over time are all critical factors in risk classification. Among management options avoidance of triggers, early risk stratification, and implantation of an Implantable Cardioverter-Defibrillator (ICD) are recommended for asymptomatic patients. For symptomatic patients, pharmacotherapy and ICD implantation are available, with the latter being a highly effective choice for treating and preventing lethal arrhythmias in BrS.

Anesthesia in patients with Brugada syndrome: two case reports

BackgroundBrugada syndrome is a rare disease. It causes sudden cardiac arrest, which is a serious life-threatening event. Sudden cardiac death mostly results from coronary artery disease. However, patients with Brugada syndrome show normal cardiac anatomy and no evidence of ischemia or electrolyte imbalance. Anesthesia in patients with Brugada syndrome is challenging due to its unpredictable nature, and is worth our attention.Case presentationWe report two cases of Brugada syndrome during anesthesia. In case one, a 31-year-old Filipino laborer was scheduled for laparoscopic appendectomy. The patient denied any preexisting cardiac disease. The preoperative vital signs were stable, with mild fever of 37.9 °C. The operation was smooth. During the emergence period, the patient suffered from sudden onset of ventricular tachycardia. After resuscitation, the cardiac rhythm returned to normal. Later, he was confirmed to have a genetic trait of Brugada syndrome. In case two, a young Taiwanese patient with pre-diagnosed Brugada syndrome underwent an operation. The perioperative precautions were taken to prevent the occurrence of ventricular arrhythmia. The surgery was uneventful.ConclusionsBrugada syndrome, although rare, has the highest incidence in South East Asian healthy young males. It brings attention to possible fatal cardiac arrhythmia in this population. Careful preoperative evaluation and perioperative management can help reduce the harmful outcome of the disease and prevent any untoward events.

Molecular mechanisms of Brugada syndrome related to p.R211H variant in RRAD gene

Brugada syndrome (BrS) is a rare inherited arrhythmic disorder with increased risk of sudden cardiac death. More than 20% of BrS cases have been linked to mutations in SCN5A gene, which encodes the voltage-gated Na+ channel Nav1.5. We have previously identified a variant (p.R211H) in RRAD gene that co-segregates with a familial form of BrS. RRAD encodes the Rad (Ras associated with diabetes) monomeric GTPase. RRAD p.R211H variant induces a reduction of the Na+ current (INa) amplitude and morphological defects in cardiomyocytes derived from human induced pluripotent stem cells (hiPS-CMs). To determine the mechanisms linking RRAD variant to INa reduction and the cardiac phenotype of a knock-in (KI) mouse model carrying the equivalent p.R210H variant. Mouse phenotyping was performed using ECG recordings, and patch-clamp technique on ventricular cardiomyocytes. Western blot and immunostaining were performed on mouse ventricular tissue and hiPSC-CMs. Co-immunoprecipitation experiments were performed on mouse ventricle and on HEK cells transfected with plasmids encoding Nav1.5 and either wild type (WT) or p.R211H-Rad. Twelve-week-old homozygous KI mice showed longer QRS complexes (12.3 ± 0.2 ms; n = 22) than WT (11.1 ± 0.2 ms; n = 13; P < 0.01) and heterozygous KI (11.7 ± 0.2 ms; n = 22) mice, a defect persisting in older mice. In homozygous KI mice INa density was decreased by 38% compared to WT mice (P < 0.01; n = 22 & 19). This was linked to a lower ventricular expression of Nav1.5 (by 49% in left ventricle; P < 0.01), Connexin 43 (Cx43; by 34%; P = 0.06) and Rad (by 33%; P < 0.01) in homozygous KI mice versus WT mice. Similar results were obtained in the hiPS-CMs of the BrS index case, in which an altered location of Rad (more nuclear than cytoplasmic) and Cx43 (lower clusters, but of larger size) was also observed, compared to control hiPS-CMs. Coimmunoprecipitation studies on left ventricular tissue of 30-week-old WT mice showed an interaction of Rad with Nav1.5, a result that was confirmed in HEKs, and of Rad with Cx43. Our results suggest that BrS-related RRAD p.R211H variant affects Rad expression and leads to a decrease of Nav1.5 and Cx43 expression, explaining both sodium current lower amplitude and conduction defects. Our results also show that Rad interacts with Nav1.5, and possibly Cx43.

PO-04-164 MOLECULAR MECHANISMS OF BRUGADA SYNDROME RELATED TO P.R211H MUTATION IN RRAD GENE

Brugada syndrome (BrS) is a rare inherited arrhythmic disorder with increased risk of sudden cardiac death. More than 20% of BrS cases have been linked to mutations in SCN5A gene, which encodes the voltage-gated Na+ channel Nav1.5. We have previously identified a novel variant (p.R211H) in RRAD gene that co-segregates with a familial form of BrS. RRAD encodes the Rad (Ras associated with diabetes) monomeric GTPase. We have shown that p.R211H RRAD variant induces a reduction of the Na+ current (INa) amplitude and morphological defects in cardiomyocytes derived from human induced pluripotent stem cells (hiPS-CMs). To characterize the cardiac phenotype of a knock-in (KI) mouse model carrying the equivalent (p.R210H) mutation and identify the mechanisms linking RRAD mutation to INa decrease and conduction defects. Mouse phenotype was determined using ECG recordings, and patch-clamp technique on ventricular cardiomyocytes. Western blot and immunostaining were performed on mouse ventricular tissue and iPSC-CMs. Co-immunoprecipitation experiments were performed on mouse ventricle and on HEK cells transfected with plasmids encoding Nav1.5 and either wild type or p.R211H-Rad. Homozygous KI mice (12 weeks old) showed longer QRS complexes (12.3±0.2 ms; n=22) than wildtype (WT; 11.1±0.2 ms; n=13; P<0.01) and heterozygous KI (11.7±0.2 ms; n=22) mice, a defect persisting in older mice. Homozygous KI mice showed a 38% decrease in INa density versus WT mice (P<0.01; n=22 & 19). This was associated with a lower ventricular expression of Nav1.5 (by 49% in left ventricle; P < 0.01) and Connexin 43 (Cx43; by 34%; P = 0.06) in homozygous KI mice versus WT mice. Rad expression was also decreased by 33% (P < 0.05). Similar results were obtained in the BrS index case hiPS-CMs, in which an altered location of Rad (more nuclear than cytoplasmic) and Cx43 (lower clusters, but of larger size) was also observed, compared to control hiPS-CMs. Coimmunoprecipitation studies on left ventricular tissue of 30-week-old WT mice showed an interaction of Rad with Nav1.5, and of Rad with Cx43. Nav1.5 interaction with Rad has been confirmed in HEK cells, which are used to determine the effect of the mutation on this interaction. To conclude, BrS-related RRAD p.R211H mutation affects Rad expression and leads to a decrease of Nav1.5 and Cx43 cardiac expression, explaining both sodium current lower amplitude and conduction defects.

Cascade screening can be life-saving: a family with multiple cases of brugada syndrome and sudden cardiac death

Brugada syndrome (BrS) may cause a spectrum of symptoms from asymptomatic patients to those who experience cardiac arrest and sudden cardiac death. The diagnosis is confirmed after observation of type I Brugada pattern on the electrocardiogram. Following the diagnosis, risk stratification can help select therapeutic options. Cascade screening should be started to find other family members with BrS. We present a 41-year-old woman diagnosed with BrS, and cascade screening of her relatives unveiled a pedigree of BrS among their family.

Ventricular Tachycardia in an Elderly Male With Brugada Syndrome.

We present a case of Brugada syndrome in a 74-year-old patient who presented with urine retention and incidentally found to have non-sustained ventricular tachycardia (NSVT) on electrocardiogram (ECG) and telemetry. To reveal characteristic type 1 Brugada pattern, right-pericardial lead was placed in the third right intercostal space. No antiarrhythmics were started, a loop recorder was implanted, and on follow-up episodes of self-terminating sustained ventricular tachycardia (VT) were noted. The patient was started on quinidine with resolution of VT.

Abstract P1099: Evidence Of Sialylation Pathway Alterations In Peripheral Blood Of Brugada Syndrome Patients

Brugada syndrome (BrS) is a cardiac arrhythmia associated with a higher risk of SCD. BrS is considered a genetic disorder, and the most commonly mutated gene is SCN5A, encoding the alpha subunit of the voltage-gated cardiac sodium channel (NaV1.5). Mutations of SCN5A usually lead to impairment of NaV1.5 functionality, which is considered the main mechanism of the disease. However, SCN5A mutations are responsible for only 30% of BrS cases. Therefore, it is conceivable that other mechanisms such as post-translational modifications (PTMs) affect NaV1.5 activity. Among others, sialylation may alter ion channel activity by carrying a sugar with a negative charge. Alterations in sialylation have been described in several cardiovascular diseases, as myocardial infarction, Chagas disease, and congenital disorders of glycosylation. For these reasons, the aim was to investigate changes in sialylation in BrS patients to obtain new information on the pathogenesis of BrS. Peripheral blood mononuclear cells (PBMCs) were collected from BrS patients and healthy controls. SNA lectin, a sialic acid-binding protein, was used to characterize the protein sialylation status of PBMCs by Western blot and flow cytometry. Gene expression of enzymes involved in the sialic acid pathway was also examined. The results showed a significant decrease in intracellular and extracellular protein sialylation levels in BrS PBMCs compared with controls. In addition, changes in gene expression of enzymes involved in the sialic acid pathway were detected. Moreover, these changes correlated with clinical parameters associated with phenotypic expression of the disease, such as arrhythmogenic BrS substrate area and potential duration. These findings support that BrS should be considered a systemic disease and are consistent with the presence of overlapping non-cardiac pathologies, as epilepsy, cancer, diabetes, skeletal muscle channelopathies, and laminopathies in BrS patients. Moreover, the discovery that molecular alterations can be found in the peripheral blood of BrS patients supports the existence of a biomarker of the disease. It is a challenge to develop an effective diagnostic test to screen broadly for BrS. In this direction, a multiomic study is ongoing in our center.

Gene therapy targeting protein trafficking regulator MOG1 in mouse models of Brugada syndrome, arrhythmias, and mild cardiomyopathy.

Brugada syndrome (BrS) is a fatal arrhythmia that causes an estimated 4% of all sudden death in high-incidence areas. SCN5A encodes cardiac sodium channel NaV1.5 and causes 25 to 30% of BrS cases. Here, we report generation of a knock-in (KI) mouse model of BrS (Scn5aG1746R/+). Heterozygous KI mice recapitulated some of the clinical features of BrS, including an ST segment abnormality (a prominent J wave) on electrocardiograms and development of spontaneous ventricular tachyarrhythmias (VTs), seizures, and sudden death. VTs were caused by shortened cardiac action potential duration and late phase 3 early afterdepolarizations associated with reduced sodium current density (INa) and increased Kcnd3 and Cacna1c expression. We developed a gene therapy using adeno-associated virus serotype 9 (AAV9) vector-mediated MOG1 delivery for up-regulation of MOG1, a chaperone that binds to NaV1.5 and traffics it to the cell surface. MOG1 was chosen for gene therapy because the large size of the SCN5A coding sequence (6048 base pairs) exceeds the packaging capacity of AAV vectors. AAV9-MOG1 gene therapy increased cell surface expression of NaV1.5 and ventricular INa, reversed up-regulation of Kcnd3 and Cacna1c expression, normalized cardiac action potential abnormalities, abolished J waves, and blocked VT in Scn5aG1746R/+ mice. Gene therapy also rescued the phenotypes of cardiac arrhythmias and contractile dysfunction in heterozygous humanized KI mice with SCN5A mutation p.D1275N. Using a small chaperone protein may have broad implications for targeting disease-causing genes exceeding the size capacity of AAV vectors.

Molecular mechanisms of Brugada syndrome related to p.R211H mutation in RRAD gene

Brugada syndrome (BrS) is a rare inherited arrhythmic disorder with increased risk of ventricular fibrillation and sudden death. More than 20% of BrS cases have been linked to mutations in the SCN5A gene, which encodes the cardiac voltage-gated sodium channel Nav1.5. We have previously identified a novel variant (p.R211H) in RRAD gene that co-segregates with a familial form of BrS. RRAD encodes the Rad (Ras associated with diabetes) small monomeric G protein. We have shown that p.R211H RRAD variant induces a reduction of the Na+ current amplitude, cytoskeleton anomalies and morphological defects in cardiomyocytes derived from induced pluripotent stem cells (iPSC-CM). Our objective is to identify the mechanisms linking RRAD mutation to those abnormalities in iPSC-CMs of the index case having the p.R211H mutation, compared to an intrafamilial control, and a knock-in (KI) mouse model carrying the equivalent (p.R210H) mutation. Western Blot and Immunostaining were performed from mouse cardiomyocytes and iPS-CMs. Homozygous KI mice (12 weeks old) showed longer QRS complex duration (12.3 ± 0.2 ms; n = 22) than wildtype (WT; 11.1 ± 0.2 ms; n = 13; P < 0.01) and heterozygous KI (11.7 ± 0.2 ms; n = 22; ns), a defect persisting in 30-week-old mice and exacerbated after ajmaline injection. Protein quantification in the left ventricle showed a lower expression of Nav1.5 (by 49%; P < 0.01) and Connexin 43 (Cx43; by 34%; P = 0.06) in 30-week-old homozygous KI mice compared to WT mice. Rad expression was also decreased by 33% ( P < 0.05). Similar results were obtained in the BrS index case iPSC-CMs, in which preliminary immunostainings also suggest an altered location of Rad and Cx43, compared to control iPSC-CMs. To conclude, p.R211H mutation of RRAD gene affects Rad expression, and leads to a decrease of Nav1.5 and Cx43 expression, explaining both sodium current lower amplitude and conduction defects.

P175 ELECTROCARDIOGRAPHIC ELEMENTS ASSOCIATED WITH ARRHYTHMIC RISK IN BRUGADA SYNDROME

Abstract Introduction Brugada syndrome is an inherited disease characterized by an increased arrhythmic risk and sudden death. The type 1 ECG pattern is the only standard required to make a diagnosis but the stratification of arrhythmic risk remains a controversial element. Some electrocardiographic signs have been described as associated with an increased arrhythmic risk. We present a case of Brugada Syndrome in which different electrocardiographic elements of incremental risk could have predicted the later evolution of the clinical case. Clinical Case A 68–year–old male patient with family history of sudden cardiac death (brother 51aa) and occasional finding of Brugada type 1 ECG pattern (2009), implanted with Medtronic bicameral ICD device in primary prevention. The electrocardiogram shows type 1 Brugada pattern in the right precordials with characteristic ST–elevation, followed by a concave ST segment, one of the signs of association with an increased arrhythmic risk; first–degree AV block with a long PR (323 msec) associated with the presence of the SCN5A mutation and an increased risk of arrhythmic events and sudden cardiac death; in the end a fragmented QRS in V2 with extended duration (153 ms). At the next follow–up the patient had some episodes of arrhythmic storm, effectively treated by the device; in consideration of the arrhythmic burden, he was subjected to epicardial ablation and was also subjected to genetic analysis that was positive for pathological mutation on the SCN5A gene (SCN5A ex 22: c.3929C&amp;gt;T;p.Pro1310Leu). Conclusions Brugada Syndrome can be diagnosed from the type 1 ECG pattern, but the current risk stratification score remains a controversial element. Electrocardiographic signs of malignancy can contribute to create a multiparametric evaluation of the patient in order to predict future arrhythmic events. Fig 1. ECG: RS 74 bpm, first–degree AV block (PR 323 msec), BFA, Brugada type 1 pattern (QRS 153 ms), fragmented QRS in V2. Fig. 2 Family tree.

PO-629-03 IN-DEPTH ANALYSIS OF THE SCN5A LOCUS HIGHLIGHTS DISTINCT GENETIC ARCHITECTURES FOR BRUGADA SYNDROME IN DIFFERENT ANCESTRIES AND IDENTIFIES A NOVEL RARE ENHANCER VARIANT ASSOCIATED WITH DISEASE IN SOUTHEAST ASIAN PATIENTS

Brugada syndrome (BrS) is a cardiac arrhythmia disorder that can cause sudden death in young adults. Genetic variation in the Nav1.5 cardiac sodium channel encoding SCN5A gene is robustly associated with BrS, across both rare coding and common non-coding variants. Despite a markedly higher prevalence of BrS, the diagnostic yield from SCN5A genetic testing in east and southeast Asia has been reported to be much lower than other regions. To compare the contribution of different classes of SCN5A variants (by variant type and rarity) to BrS between northwest European and Thai populations in order to investigate the apparent paradox between high disease prevalence and low diagnostic yield in southeast Asia. Genome sequencing data from European (412 cases, 769 controls) and Thai (202 cases, 410 controls) samples was analysed. SCN5A coding variants were binned by gnomAD exomes (v2.1) filtering allele frequency (FAF) and case-control odds ratios (OR) were calculated for each bin and ancestry. Rare non-coding variants in promoter and enhancer regions of SCN5A and SCN10A were assessed for enrichment or depletion in BrS cohorts. Ultra-rare (FAF<0.00001) SCN5A coding variants are more prevalent and enriched in European (22.6% of cases, OR=22.1, 11.4-43.0) compared to Thai (5.9% of cases, OR=4.3, 1.6-11.5) BrS patients. In contrast, low frequency variants (FAF 0.00005-0.001) that are expected to have intermediate effect sizes are uniquely enriched in Thai samples, occurring in 9.9% of patients. 3/6 of these variants (p.R965C, p.A1428S, p.V2016M) are known to affect Nav1.5 function. A rare non-coding variant in the SCN5A RE5 enhancer region (GRCh37:3-38621871-A-C), affecting a base conserved across species, was highly and uniquely enriched in Thai BrS cases (4.5% vs 0.2%, OR=19.1, p=3e-04). Distinct SCN5A genetic architectures are observed in European and southeast Asian BrS patients. The increased prevalence of BrS in southeast Asia is not due to an increased population burden of ultra-rare and highly deleterious SCN5A coding variants (which are relatively depleted in case cohorts). Our data suggest that other SCN5A variant classes, including coding variants of intermediate effect size and rare non-coding enhancer variants, are genetic risk factors in Thai BrS cases.

Brugada Syndrome in Women: What Do We Know After 30 Years?

Brugada syndrome (BrS) was initially described in 1992 by Josep and Pedro Brugada as an arrhythmogenic disease characterized by ST segment elevation in the right precordial leads and increased risk of sudden cardiac death (SCD). Alterations in the SCN5A gene are responsible for approximately 30% of cases of BrS, following an autosomal dominant pattern of inheritance. However, despite its autosomal transmission, sex-related differences are widely accepted. BrS is more prevalent in males than in females (8–10 times), with males having a 5.5-fold higher risk of SCD. There are also differences in clinical presentation, with females being more frequently asymptomatic and older than males at the time of diagnosis. Some factors have been identified that could explain these differences, among which testosterone seems to play an important role. However, only 30% of the available publications on the syndrome include sex-related information. Therefore, current findings on BrS are based on studies conducted mainly in male population, despite the wide acceptance of gender differences. The inclusion of complete clinical and demographic information in future publications would allow a better understanding of the phenotypic variability of BrS in different age and sex groups helping to improve the diagnosis, management and risk management of SCD.

Dominant negative effects of SCN5A missense variants

PurposeUp to 30% of patients with Brugada syndrome (BrS) carry loss-of-function (LoF) variants in the cardiac sodium channel gene SCN5A encoding for the protein NaV1.5. Recent studies suggested that NaV1.5 can dimerize, and some variants exert dominant negative effects. In this study, we sought to explore the generality of missense variant NaV1.5 dominant negative effects and their clinical severity. MethodsWe identified 35 LoF variants (<10% of wild type [WT] peak current) and 15 partial LoF variants (10%-50% of WT peak current) that we assessed for dominant negative effects. SCN5A variants were studied in HEK293T cells, alone or in heterozygous coexpression with WT SCN5A using automated patch clamp. To assess the clinical risk, we compared the prevalence of dominant negative vs putative haploinsufficient (frameshift, splice, or nonsense) variants in a BrS consortium and the Genome Aggregation Database population database. ResultsIn heterozygous expression with WT, 32 of 35 LoF and 6 of 15 partial LoF variants showed reduction to <75% of WT-alone peak current, showing a dominant negative effect. Individuals with dominant negative LoF variants had an elevated disease burden compared with the individuals with putative haploinsufficient variants (2.7-fold enrichment in BrS cases, P = .019). ConclusionMost SCN5A missense LoF variants exert a dominant negative effect. This class of variant confers an especially high burden of BrS.

Clinical presentation and electrocardiographic features of Brugada syndrome in Iraq

Background: Brugada syndrome is a clinical entity composed of twelve leads electrocardiographic changes of coved or saddle shaped ST-segment elevation in V1 and V2 with serious ventricular arrhythmias which may cause sudden cardiac death. Objectives: The objectives of this study is to highlight the clinical presentation and the types of ECG changes of Brugada syndrome cases seen in Iraq and to orient physicians about this fatal condition. Patients and Methods: Patients presented with symptoms of palpitation, dizzy attacks or syncope and diagnosed as Brugada syndrome were included in this case series study. The diagnosis of Brugada syndrome based mainly on the typical coved or saddle shaped or variant ST-Segment elevation in electrocardiographic leads V1, V2. Results: Eighteen patients were included in this case series study. All are males. Age ranged from 15-45 Y. The presenting symptoms were palpitation in 12 patients, syncope in 8, dizzy spells and pre syncope in 14 and chest pain seen in 2. The arrhythmic events were clinically documented in 10. Monomorphic VT seen in 4, VF in 2, atrial fibrillation in 2 and atrial flutter in 2. Induced VF by EP study seen in 2. Type I Brugada ECG pattern was seen in 6 patients, type II in 4 and three of type III. Five showed a variant type of the syndrome. Family history of sudden cardiac death was seen in 8 patients while in 10 it was negative. ICD was implanted in 6 patients. In 12 patients (67%) the diagnosis of Brugada syndrome was missed during the provisional medical contacts. Conclusion: Brugada syndrome is not uncommon in Iraq but needs a high diagnostic suspicion through appreciating the symptomologies and electrocardiographic features of this fatal syndrome to plan management to prevent sudden cardiac death. Key words: Brugada syndrome, Iraq