Electrocardiographic characteristics and SCN5A mutations in idiopathic ventricular fibrillation associated with early repolarization

In silico validation revealed the role of SCN5A mutations and their genotype-phenotype correlations in Brugada syndrome

BACKGROUND

Brugada syndrome (BrS) is a rare genetic disease that causes sudden cardiac death (SCD) and arrhythmia. SCN5A pathogenic variants (about 30% of diagnosed patients) are responsible for BrS.

AIMS

Lack of knowledge regarding molecular characteristics and the correlation between genotype and phenotype interfere with the risk stratification and finding the optimal treatment in Vietnam. Therefore, we identified SCN5A variants and evaluated the genotype-phenotype correlation of BrS on 117 Vietnamese probands.

MATERIALS AND METHODS

The clinical characteristics and blood samples of BrS patients were collected. To determine SCN5A variants, Sanger sequencing was conducted, and subsequently, these variants were analyzed by bioinformatic tools.

RESULTS

In this cohort, the overall rate of detected variants in SCN5A was 25.6%, which could include both pathogenic and benign variants. In genetic testing, 21 SCN5A variants were identified, including eight novels and 15 published variants. Multiple bioinformatic tools were used to predict variant effect with c.551A>G, c.1890+14G>A, c.3338C>T, c.3578G>A, and c.5484C>T as benign, while other variants were predicted as disease-causing. The family history of SCD (risk ratio [RR] = 4.324, 95% CI: 2.290-8.269, p < 0.001), syncope (RR = 3.147, 95% CI: 1.668-5.982, p = 0.0004), and ventricular tachycardia/ventricular fibrillation (RR = 3.406, 95% CI: 1.722-5.400, p = 0.0035) presented a significantly higher risk in the SCN5A (+) group, consisting of individuals carrying any variant in the SCN5A gene, compared to SCN5A (-) individuals.

CONCLUSION

The results contribute to clarifying the impact of SCN5A variants on these phenotypes. Further follow-up studies need to be carried out to understand the functional effects of these SCN5A variants on the severity of BrS.

Early Repolarization Augmentation Mimicking Pseudo-Infarction in a Patient With Diabetic Ketoacidosis and Normokalemia

Early repolarization (ER) changes, characterized by J point elevation with or without ST-segment elevation, are dynamic in their presentation and can be exacerbated by factors such as hypothermia, hypercalcemia, vagotonia, and certain medications. There is limited research regarding the mechanism of these changes and the dynamic changes of ER secondary to diabetic ketoacidosis (DKA). This case report highlights the augmentation of early repolarization changes resembling ST-segment elevation myocardial infarction (STEMI) in a patient with DKA that resolved with the treatment of acidosis. The misinterpretation of ER changes on electrocardiogram (ECG) as STEMI or pericarditis may result in the inappropriate utilization of resources, increased patient risk, and elevated morbidity and mortality. Recognition of the potential of DKA to cause ER changes can potentially avoid these unfavorable outcomes.

Novel SCN5A frame‑shift mutation underlying in patient with idiopathic ventricular fibrillation manifested with J wave in inferior lead and prolonged S‑wave in precordial lead

Mutations in the SCN5A gene has been recognized as resulting in a series of life-threatening arrhythmias. However, it also causes idiopathic ventricular fibrillation (IVF) with J wave in inferior leads and prolonged S-wave upstroke in precordial leads, which has not been previously reported. The present study aimed to study the mechanisms of a patient with IVF manifested with J wave in inferior leads and prolonged S-wave upstroke in precordial leads. The electrocardiograms (ECG) of the proband were recorded and genetic testing was conducted. Patch-clamp and immunocytochemical studies were performed in heterologously transfected 293 cells. The VF attacks was documented in a 55-year-old male proband with syncope episodes. 12-lead ECG shown the transient J wave in the inferior leads and prolonged S-wave upstroke in precordial V1-V3 leads in the same timeframe. Genetic analysis revealed a novel 1 base deletion (G) at position 839 in exon 2 in SCN5A gene (C280S*fs61), which causes a severe truncation of the sodium channel. The functional study revealed that in 293 cells transfected with mutant channel, no sodium current could be recorded even though the immunocytochemical experiment confirmed the truncated sodium channel existed in cytosol. The kinetics of the wild-type (WT) channel were not altered when co-transfected with C280S*fs61 mutant which suggested a haploinsufficiency effect of sodium channel in the cells. The present study identified a novel C280Sfs*61 mutation that caused the 'loss of function' of the sodium channel by haploinsufficiency mechanism. The reduced sodium channel function in the heart may cause conduction delay that may underlie the manifestation of J wave and prolonged S-wave upstroke associated with IVF.

Subepicardial Cardiomyopathy: A Disease Underlying J-Wave Syndromes and Idiopathic Ventricular Fibrillation

Brugada syndrome (BrS), early repolarization syndrome (ERS), and idiopathic ventricular fibrillation (iVF) have long been considered primary electrical disorders associated with malignant ventricular arrhythmia and sudden cardiac death. However, recent studies have revealed the presence of subtle microstructural abnormalities of the extracellular matrix in some cases of BrS, ERS, and iVF, particularly within right ventricular subepicardial myocardium. Substrate-based ablation within this region has been shown to ameliorate the electrocardiographic phenotype and to reduce arrhythmia frequency in BrS. Patients with ERS and iVF may also exhibit low-voltage and fractionated electrograms in the ventricular subepicardial myocardium, which can be treated with ablation. A significant proportion of patients with BrS and ERS, as well as some iVF survivors, harbor pathogenic variants in the voltage-gated sodium channel gene, SCN5A, but the majority of genetic susceptibility of these disorders is likely to be polygenic. Here, we postulate that BrS, ERS, and iVF may form part of a spectrum of subtle subepicardial cardiomyopathy. We propose that impaired sodium current, along with genetic and environmental susceptibility, precipitates a reduction in epicardial conduction reserve, facilitating current-to-load mismatch at sites of structural discontinuity, giving rise to electrocardiographic changes and the arrhythmogenic substrate.

Sinus Rhythm Electrocardiographic Abnormalities, Sites of Origin, and Ablation Outcomes of Ventricular Premature Depolarizations Initiating Ventricular Fibrillation

BACKGROUND

Ventricular fibrillation (VF) can be initiated by ventricular premature depolarizations (VPDs) in the absence of obvious structural abnormalities.

OBJECTIVE

To determine the prevalence of 12-lead ECG sinus rhythm reduced QRS amplitude, QRS fractionation (QRSf) and early repolarization (ER) pattern, and the outcome of catheter ablation and VPD anatomic distribution in patients with VPDs initiating VF.

METHODS

We compared a cohort with no apparent structural heart disease and VPDs initiating VF (Group 1, n=42) to a reference cohort (Group 2, n=61) of patients with no structural heart disease and symptomatic unifocal VPDs.

RESULTS

A reduced QRS amplitude (<.55 mV) in aVF (59 % vs 10%, p<0.001), QRSf in ≥2 contiguous leads (50% vs 16%, p<0.001) and early repolarization pattern (21.4% vs 1.6%, p=0.01) were more common in Group 1 vs Group 2. At least one abnormal ECG finding was present in 34 (81%) Group 1 vs 17 (28%) Group 2 patients, (p<0.001). VPD origin included RV and LV distal Purkinje system and moderator band/ papillary muscles, in 83% Group 1 vs 18% Group 2 patients, p<0.001. VF was eliminated with single ablation procedure in 77% of Group 1 patients with at least 2 years of follow-up.

CONCLUSIONS

A reduced QRS amplitude (<.55 mV) in aVF, QRS fractionation in ≥2 contiguous leads and/or an early repolarization pattern are frequently observed in patients with VPDs initiating VF. VPDs initiating VF typically originate from the distal Purkinje system and papillary muscles and can be successfully eliminated with catheter ablation.

Sudden Cardiac Death Risk Stratification of the Early Repolarization Syndrome: An Updated Review of the Literature

PURPOSE OF REVIEW

Early repolarization syndrome (ERS), once thought to be innocuous, has now been shown to be responsible for ventricular arrythmias and sudden cardiac death occurrence. This review will help the clinician to identify the patients who are most at risk for arrhythmias, so that they can adopt a preventive or secondary treatment approach, either of which is still poorly defined.

RECENT FINDINGS

Patients at high risk are found to be particularly young men, with a personal or family history of syncope or sudden death, who have an inferolateral ER on the electrocardiogram, more elevated J-point, longer J-wave duration and wider J angle, a horizontal or descending ST segment, lower T/R ratio, and small and/or inverted waves. The association with a structural heart disease or another channelopathy potentiates this arrhythmic risk. Taken together, these parameters allow prediction of the malignancy of ER pattern with a certain reliability. Further research is however needed to develop concrete risk stratification algorithms and the therapeutic strategies taken in function of it.

Delayed depolarization and histologic abnormalities underlie the Brugada syndrome

Brugada syndrome (BrS) is a controversial disease whose pathophysiology is still far from being fully understood. Unlike other cardiological disorders, a definite etiology has not yet been established so that it could be summarized under two main chapters: "functional" or "organic", "repolarization" or "depolarization" disorder. Despite initial descriptions leaned towards the organic substrate and delayed depolarization features, functional and repolarization theories have attracted most of the Cardiological attention for many years. Data from electrocardiography, endocavitary tracings, electroanatomic mapping and histopathology, however, demonstrated that BrS is mainly characterized by structural myocardial changes mostly at the right ventricular outflow tract (RVOT), but also at the right ventricle (RV) and by delayed conduction at the same sites. Conduction disorders at different levels may also be present and identify patients at high risk for major arrhythmic events. The aim of the present review is to provide the current state of art of the pathophysiology of BrS, focusing on electro-vectorcardiography and electrophysiological features, histopathology, echocardiography, and cardiac magnetic resonance imaging (CMRI).

Electrocardiographic features in SCN5A mutation-positive patients with Brugada and early repolarization syndromes: a systematic review and meta-analysis

Background

Early repolarization syndrome (ERS) and Brugada syndrome (BrS) are both J-wave syndromes. Both can involve mutations in the SCN5A gene but may exhibit distinct electrocardiographic (ECG) differences. The aim of this systematic review and meta-analysis is to investigate possible differences in ECG markers between SCN5A-positive patients with ERS and BrS.

Methods

PubMed and Embase were searched from their inception to 20 October 2021 for human studies containing the search terms “SCN5A” and “variant” and “early repolarization” or “Brugada”, with no language restrictions. Continuous variables were expressed as mean±standard deviation. PR interval, QRS duration, QTc and heart rate from the included studies were pooled to calculate a mean for each variable amongst BrS and ERS patients. A two-tailed Student’s t test was then performed to for comparisons.

Results

A total of 328 studies were identified. After full-text screening, 12 studies met our inclusion criteria and were included in this present study. One hundred and four ERS patients (mean age 30.86±14.45) and 2000 BrS patients (mean age 36.17±11.39) were studied. Our meta-analysis found that ERS patients had shorter QRS duration (90.40±9.97 vs. 114.79±20.10, P = 0.0001) and shorter corrected QT intervals (QTc) with borderline significance (393.63±40.04 vs. 416.82±37.43, P = 0.052). By contrast, no significant differences in baseline heart rate (65.15±18.78 vs. 76.06±18.78, P = 0.068) or PR intervals (197.40±34.69 vs. 191.88±35.08, P = 0.621) were observed between ERS and BrS patients.

Conclusion

BrS patients with positive SCN5A mutations exhibited prolonged QRS, indicating conduction abnormalities, whereas ERS patients with positive SCN5A mutations showed normal QRS. By contrast, whilst QTc intervals were longer in BrS than in ERS SCN5A positive patients, they were within normal limits. Further studies are needed to examine the implications of these findings for arrhythmic risk stratification.

Latent Causes of Sudden Cardiac Arrest

Inherited arrhythmia syndromes are a common cause of apparently unexplained cardiac arrest or sudden cardiac death. These include long QT syndrome and Brugada syndrome, with a well-recognized phenotype in most patients with sufficiently severe disease to lead to cardiac arrest. Less common and typically less apparent conditions that may not be readily evident include catecholaminergic polymorphic ventricular tachycardia, short QT syndrome and early repolarization syndrome. In cardiac arrest patients whose extensive testing does not reveal an underlying etiology, a diagnosis of idiopathic ventricular fibrillation or short-coupled ventricular fibrillation is assigned. This review summarizes our current understanding of the less common inherited arrhythmia syndromes and provides clinicians with a practical approach to diagnosis and management.

Genomic and Non-Genomic Regulatory Mechanisms of the Cardiac Sodium Channel in Cardiac Arrhythmias

Nav1.5 is the predominant cardiac sodium channel subtype, encoded by the SCN5A gene, which is involved in the initiation and conduction of action potentials throughout the heart. Along its biosynthesis process, Nav1.5 undergoes strict genomic and non-genomic regulatory and quality control steps that allow only newly synthesized channels to reach their final membrane destination and carry out their electrophysiological role. These regulatory pathways are ensured by distinct interacting proteins that accompany the nascent Nav1.5 protein along with different subcellular organelles. Defects on a large number of these pathways have a tremendous impact on Nav1.5 functionality and are thus intimately linked to cardiac arrhythmias. In the present review, we provide current state-of-the-art information on the molecular events that regulate SCN5A/Nav1.5 and the cardiac channelopathies associated with defects in these pathways.

Distinct Features of Probands With Early Repolarization and Brugada Syndromes Carrying SCN5A Pathogenic Variants

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.

Transcriptional profiles of genes related to electrophysiological function in Scn5a+/- murine hearts

The Scn5a gene encodes the major pore-forming Nav 1.5 (α) subunit, of the voltage-gated Na+ channel in cardiomyocytes. The key role of Nav 1.5 in action potential initiation and propagation in both atria and ventricles predisposes organisms lacking Scn5a or carrying Scn5a mutations to cardiac arrhythmogenesis. Loss-of-function Nav 1.5 genetic abnormalities account for many cases of the human arrhythmic disorder Brugada syndrome (BrS) and related conduction disorders. A murine model with a heterozygous Scn5a deletion recapitulates many electrophysiological phenotypes of BrS. This study examines the relationships between its Scn5a+/- genotype, resulting transcriptional changes, and the consequent phenotypic presentations of BrS. Of 62 selected protein-coding genes related to cardiomyocyte electrophysiological or homeostatic function, concentrations of mRNA transcribed from 15 differed significantly from wild type (WT). Despite halving apparent ventricular Scn5a transcription heterozygous deletion did not significantly downregulate its atrial expression, raising possibilities of atria-specific feedback mechanisms. Most of the remaining 14 genes whose expression differed significantly between WT and Scn5a+/- animals involved Ca2+ homeostasis specifically in atrial tissue, with no overlap with any ventricular changes. All statistically significant changes in expression were upregulations in the atria and downregulations in the ventricles. This investigation demonstrates the value of future experiments exploring for and clarifying links between transcriptional control of Scn5a and of genes whose protein products coordinate Ca2+ regulation and examining their possible roles in BrS.

Prevalence and electrophysiological phenotype of rare SCN5A genetic variants identified in unexplained sudden cardiac arrest survivors

AIMS

To determine the prevalence and in vitro electrophysiological (EP) phenotype of ultra-rare SCN5A variants of uncertain significance (VUS) identified in unexplained sudden cardiac arrest (SCA) survivors.

METHODS AND RESULTS

Retrospective review of 73 unexplained SCA survivors was used to identify all patients that underwent a form of genetic testing that included comprehensive SCN5A analysis. Ultra-rare SCN5A variants (minor allele frequency < 0.005) were adjudicated according to the 2015 American College of Medical Genetics and Genomics (ACMG) guidelines. Variants designated as VUS were expressed heterologously and characterized using the whole-cell patch clamp technique. Overall, 60/73 (82%; the average age at SCA 28 ± 12 years) unexplained SCA survivors had received SCN5A genetic testing. Of these, 5/60 (8.3%) had an ultra-rare SCN5A variant. All SCN5A variants were classified as VUS. Whereas the single SCN5A VUS (p.Asp872Asn-SCN5A) identified in an unexplained SCA survivor with PR interval prolongation and inferior early repolarization conferred a loss-of-function phenotype (46.2% reduction in peak current density; 16 ms slower recovery from inactivation), the four other SCN5A VUS (p.Glu30Gly-SCN5A, p.Gln245Lys-SCN5A, p.Pro648Leu-SCN5A, and p.Glu1240Gln-SCN5A) identified in unexplained SCA survivors without early repolarization/conduction delay were indistinguishable from wild-type Nav1.5 channels.

CONCLUSION

In the absence of a phenotype(s) potentially attributable to sodium channel dysfunction, all SCN5A VUS identified in unexplained SCA survivors conferred a wild-type EP phenotype in vitro. As the background rate of SCN5A genetic variation is not trivial, great care must be taken to avoid prioritizing genotype over phenotype when attempting to ascertain the root cause of an individual's SCA.

Clinical and Functional Genetic Characterization of the Role of Cardiac Calcium Channel Variants in the Early Repolarization Syndrome

Background: Early repolarization syndrome (ERS) is an inherited sudden cardiac death (SCD) syndrome. The present study investigates the role of genetic variants in cardiac calcium-channel genes in the pathogenesis of ERS and probes the underlying mechanisms. Methods: Polymerase chain reaction-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 coexpressed with CACNB2b and CACNA2D1 in HEK293 cells and studied using whole-cell patch-clamp techniques 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 (62.5%), and 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 beats/min, * p < 0.05), QTc interval was shorter (408.2 ± 21.4 vs. 386.8 ± 16.9 ms, ** p < 0.01), and Tp-e/QT was longer (0.22 ± 0.05 vs. 0.28 ± 0.04, *** p < 0.001) in single calcium mutation carriers. Electrophysiological analysis of one mutation, CACNA1C-P817S (c.2449C>T), revealed that the density of whole-cell calcium current (I Ca) was reduced by ~84.61% compared to WT (-3.17 ± 2.53 vs. -20.59 ± 3.60 pA/pF, n = 11 and 15, respectively, ** p < 0.01). Heterozygous expression of mutant channels was associated with a 51.35% reduction of I Ca. Steady-state inactivation was shifted to more negative potentials and significantly accelerated as well. Confocal microscopy revealed trafficking impairment of CACNA1C-P817S (peripheral/central intensity: 0.94 ± 0.10 in WT vs. 0.33 ± 0.12 in P817S, n = 10 and 9, respectively, ** p < 0.01). 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.

Towards Mutation-Specific Precision Medicine in Atypical Clinical Phenotypes of Inherited Arrhythmia Syndromes

Most causal genes for inherited arrhythmia syndromes (IASs) encode cardiac ion channel-related proteins. Genotype-phenotype studies and functional analyses of mutant genes, using heterologous expression systems and animal models, have revealed the pathophysiology of IASs and enabled, in part, the establishment of causal gene-specific precision medicine. Additionally, the utilization of induced pluripotent stem cell (iPSC) technology have provided further insights into the pathophysiology of IASs and novel promising therapeutic strategies, especially in long QT syndrome. It is now known that there are atypical clinical phenotypes of IASs associated with specific mutations that have unique electrophysiological properties, which raises a possibility of mutation-specific precision medicine. In particular, patients with Brugada syndrome harboring an SCN5A R1632C mutation exhibit exercise-induced cardiac events, which may be caused by a marked activity-dependent loss of R1632C-Nav1.5 availability due to a marked delay of recovery from inactivation. This suggests that the use of isoproterenol should be avoided. Conversely, the efficacy of β-blocker needs to be examined. Patients harboring a KCND3 V392I mutation exhibit both cardiac (early repolarization syndrome and paroxysmal atrial fibrillation) and cerebral (epilepsy) phenotypes, which may be associated with a unique mixed electrophysiological property of V392I-Kv4.3. Since the epileptic phenotype appears to manifest prior to cardiac events in this mutation carrier, identifying KCND3 mutations in patients with epilepsy and providing optimal therapy will help prevent sudden unexpected death in epilepsy. Further studies using the iPSC technology may provide novel insights into the pathophysiology of atypical clinical phenotypes of IASs and the development of mutation-specific precision medicine.

High-risk atrioventricular block in Brugada syndrome patients with a history of syncope

BACKGROUND

Determining the etiology of syncope is challenging in Brugada syndrome (BrS) patients. Implantable cardioverter defibrillator placement is recommended in BrS patients who are presumed to have arrhythmic syncope. However, arrhythmic syncope in BrS patients can occur in the setting of atrioventricular block (AVB), which should be managed by cardiac pacing. The clinical characteristics of BrS patients with high-risk AVB remain unknown.

METHODS

This study included 223 BrS patients with a history of syncope from two centers. The clinical characteristics of patients with high-risk AVB (Mobitz type II second-degree AVB, high-degree AVB, or third-degree AVB) were investigated.

RESULTS

During the 99 ± 78 months of follow-up, we identified six BrS patients (2.7%) with high-risk AVB. Three of the six patients (50%) with AVB presented with syncope associated with prodromes or specific triggers. Four patients (67%) were found to have paroxysmal third-degree AVB during the initial evaluation for BrS and syncope, while two patients developed third-degree AVB during the follow-up period. The incidence of first-degree AVB was significantly higher in AVB patients than in non-AVB patients (83% vs. 15%; p = .0005). There was no significant difference in the incidence of ventricular fibrillation between AVB and non-AVB patients (AVB [17%], non-AVB [12%]; p = .56).

CONCLUSION

High-risk AVB can occur in BrS patients with various clinical presentations. Although rare, the incidence is worth considering, especially in BrS patients with first-degree AVB.

Susceptibility to Ventricular Arrhythmias Resulting from Mutations in FKBP1B, PXDNL, and SCN9A Evaluated in hiPSC Cardiomyocytes

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 I_Ca in the proband compared with control. Coexpression of PXDNL-R391Q with SCN5A-WT displayed lower I_Na density compared to PXDNL-WT. 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.

Direct and Indirect Suppression of Scn5a Gene Expression Mediates Cardiac Na+ Channel Inhibition by Wnt Signalling

BACKGROUND

Myocardial infarction and heart failure are associated with reduced voltage-gated Na⁺ current (I_Na) that promotes arrhythmias and sudden deaths. We have previously shown that the Wnt/β-catenin signalling (Wnt signalling), which is active in heart disease, reduces cardiac I_Na, suggesting that Wnt signalling may be a potential therapeutic target. However, because Wnt signalling is required for the homeostasis of many noncardiac tissues, administration of Wnt inhibitors to heart patients would cause significant side effects. The present study aims to elucidate the molecular mechanisms of cardiac I_Na inhibition by Wnt, which would identify cardiac-specific therapeutic targets.

METHODS

Wnt signalling was activated in neonatal rat ventricular myocytes by Wnt3a protein. Adenovirus expressing Wnt3a was injected into the adult rat ventricle. CRISPR/Cas9 and chromatin immunoprecipitation were used for mechanistic studies.

RESULTS

Wnt signalling activation in neonatal rat ventricular myocytes reduced Na_v1.5 protein and Scn5a mRNA, but increased Tbx3, a known suppressor of Scn5a. Chromatin immunoprecipitation showed that Wnt signalling inhibits Scn5a expression through downstream mediator (TCF4) binding to both Tbx3 and Scn5a promoters. Overexpression or knockdown of Tbx3 directly modified Na_v1.5 and I_Na, whereas CRISPR/Cas9-induced mutations at TCF4 binding sites within the Scn5a promoter attenuated Wnt inhibition of Scn5a and Na_v1.5. In adult rat hearts, adenovirus expressing Wnt3a reduced Na_v1.5, increased QRS duration in electrocardiogram, and increased the susceptibility to ventricular tachycardia.

CONCLUSIONS

Wnt signalling inhibits the Na⁺ channel by direct and indirect (via Tbx3) suppression of Scn5a transcription. Strategies to block TCF4 binding to the Tbx3 and Scn5a promoters would represent novel strategies for cardiac-specific inhibition of the Wnt pathway to rescue I_Na and prevent sudden cardiac deaths.

Long-term prognosis of patients withJ-wave syndrome

OBJECTIVE

Limited data are currently available regarding the long-term prognosis of patients with J-wave syndrome (JWS). The aim of this study was to investigate the long-term prognosis of patients with JWS and identify predictors of the recurrence of ventricular fibrillation (VF).

METHODS

This was a multicentre retrospective study (seven Japanese hospitals) involving 134 patients with JWS (Brugada syndrome (BrS): 85; early repolarisation syndrome (ERS): 49) treated with an implantable cardioverter defibrillator. All patients had a history of VF. All patients with ERS underwent drug provocation testing with standard and high intercostal ECG recordings to rule out BrS. The impact of global J waves (type 1 ECG or anterior J waves and inferolateral J waves in two or more leads) on the prognosis was evaluated.

RESULTS

During the 91±66 months of the follow-up period, 52 (39%) patients (BrS: 37; ERS: 15) experienced recurrence of VF. Patients with BrS and ERS with global J waves showed a significantly higher incidence of VF recurrence than those without (BrS: log-rank, p=0.014; ERS: log-rank, p=0.0009). The presence of global J waves was a predictor of VF recurrence in patients with JWS (HR: 2.16, 95% CI 1.21 to 3.91, p=0.0095), while previously reported high-risk electrocardiographic parameters (high-amplitude J waves ≥0.2 mV and J waves associated with a horizontal or descending ST segment) were not predictive of VF recurrence.

CONCLUSIONS

This multicentre long-term study showed that the presence of global J waves was associated with a higher incidence of VF recurrence in patients with JWS.

A de novo gain-of-function KCND3 mutation in early repolarization syndrome

BACKGROUND

Early repolarization syndrome (ERS) is characterized by J-point elevation on electrocardiograms and ventricular fibrillation (VF). Early repolarization arises from augmentation of the transmural electrical gradient in the cardiac action potential; therefore, the transient outward potassium current (I_to) has been regarded as a key candidate current for elucidating the mechanism of ERS. KCND3 encoding Kv4.3, an α-subunit of the I_to channel, is considered as one of target genes.

OBJECTIVE

The purpose of this study was to search for novel KCND3 mutations associated with ERS and to clarify the pathogenesis.

METHODS

We performed genetic screening for 11 unrelated probands with ERS and analyzed the electrophysiological properties of detected mutations by patch-clamp methods.

RESULTS

A novel de novo KCND3 heterozygous mutation, Gly306Ala (c.917g>c), was found in 1 proband. The proband was a 12-year-old boy, who suffered VF storm and showed significant J-point elevation in multiple leads. Intravenous isoproterenol and subsequent administration of quinidine were effective in preventing VF recurrence and restored the J-point elevation. In electrophysiological analysis, cultured cells expressing mutant Kv4.3 showed significantly increased current densities, slow inactivation, and slow recovery from inactivation compared to wild type. Extracellular application of quinidine significantly restored the inactivation time course in mutant Kv4.3. A simulation study confirmed the relationship between the novel KCND3 mutation and early repolarization on electrocardiograms.

CONCLUSION

A novel KCND3 heterozygous mutation was found to be associated with ERS. The pathogenesis can be explained by the increased I_to. Genetic screening for KCND3 could be useful for understanding the pathogenesis and selecting effective treatment.

Early Repolarization Syndrome: Diagnostic and Therapeutic Approach

An early repolarization pattern can be observed in 1% up to 13% of the overall population. Whereas, this pattern was associated with a benign outcome for many years, several more recent studies demonstrated an association between early repolarization and sudden cardiac death, so-called early repolarization syndrome. In early repolarization syndrome patients, current imbalances between epi- and endo-cardial layers result in dispersion of de- and repolarization. As a consequence, J waves or ST segment elevations can be observed on these patients' surface ECGs as manifestations of those current imbalances. Whereas, an early repolarization pattern is relatively frequently found on surface ECGs in the overall population, the majority of individuals presenting with an early repolarization pattern will remain asymptomatic and the isolated presence of an early repolarization pattern does not require further intervention. The mismatch between frequently found early repolarization patterns in the overall population, low incidences of sudden cardiac deaths related to early repolarization syndrome, but fatal, grave consequences in affected patients remains a clinical challenge. More precise tools for risk stratification and identification of this minority of patients, who will experience events, remain a clinical need. This review summarizes the epidemiologic, pathophysiologic and diagnostic background and presents therapeutic options of early repolarization syndrome.

Electrophysiological Basis for Early Repolarization Syndrome

During last centuries, Early Repolarization pattern has been interpreted as an ECG manifestation not linked to serious cardiovascular events. This view has been challenged on the basis of sporadic clinical observations that linked the J-wave with ventricular arrhythmias and sudden cardiac death. The particular role of this characteristic pattern in initiating ventricular fibrillation has been sustained by clinical descriptions of a marked and consistent J-wave elevation preceding the onset of the ventricular arrhythmia. Until now, Early Repolarization syndrome patients have been evaluated using ECG and theorizing different interpretations of the findings. Nonetheless, ECG analysis is not able to reveal all depolarization and repolarization properties and the explanation for this clinical events. Recent studies have characterized the epicardial substrate in these patients on the basis of high-resolution data, in an effort to provide insights into the substrate properties that support arrhythmogenicity in these patients. An overview for the current evidence supporting different theories explaining Early Repolarization Syndrome is provided in this review. Finally, future developments in the field directed toward individualized treatment strategies are examined.

The narrow-sense and common single nucleotide polymorphism heritability of early repolarization

BACKGROUND

Early repolarization (ER) is a risk marker for sudden cardiac death. Higher risk is associated with horizontal/descending ST-segment ER in the inferior or inferolateral ECG leads. Studies in family cohorts have demonstrated substantial heritability for the ER pattern, but genome-wide association studies (GWAS) have failed to identify statistically significant and replicable genetic signals.

METHODS AND RESULTS

We assessed the narrow-sense and common single nucleotide polymorphism (SNP) heritability of ER and ER subtypes using ECG data from 5829 individuals (TwinsUK, BRIGHT and GRAPHIC cohorts). ER prevalence was 8.3%. In 455 monozygous vs 808 dizygous twin pairs, concordances and twin correlations for ER subtypes (except horizontal/descending ST-segment ER) were higher and familial resemblance (except notched ER) was significant. Narrow-sense heritability estimates derived from 1263 female twin pairs using the structural equation program Mx ranged from 0.00-0.47 and common SNP heritability estimates derived from 4009 unrelated individuals of both sexes using Genome-wide Restricted Maximum Likelihood (GREML) ranged from 0.00-0.36, but none were statistically significant.

CONCLUSION

From our data, ER shows limited genetic predisposition. There appears to be significant environmental influence and these modest narrow-sense and common SNP heritability estimates may explain why previous GWAS have been unsuccessful.

J wave syndromes as a cause of malignant cardiac arrhythmias

The J wave syndromes, including the Brugada (BrS) and early repolarization (ERS) syndromes, are characterized by the manifestation of prominent J waves in the electrocardiogram appearing as an ST segment elevation and the development of life-threatening cardiac arrhythmias. BrS and ERS differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J wave syndromes. Despite over 25 years of intensive research, risk stratification and the approach to therapy of these two inherited cardiac arrhythmia syndromes are still rapidly evolving. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, as well as the molecular, ionic, cellular, and genetic mechanisms underlying these two syndromes that have captured the interest and attention of the cardiology community over the past two decades.

Feasibility evaluation of long-term use of beta-blockers and calcium antagonists in patients with Brugada syndrome

Aims

Beta-blockers (BBs) and calcium antagonists (CAs) are reported to aggravate ST-segment elevation in some patients with Brugada syndrome (BrS). The feasibility of their long-term use in BrS still remains unknown. We investigated the safety of long-term use of BB and CA in BrS patients.

Methods and results

Of the 360 consecutive BrS patients, 29 [5: a history of ventricular fibrillation (VF), 17: syncope, 7: asymptomatic] took BB and/or CA (BB: 22, CA: 8) for more than 1 year for the treatment of co-morbidities such as atrial tachyarrhythmia, vasospastic angina, and neurally mediated syncope. The electrocardiographic changes and clinical outcome after the treatment were evaluated. Eleven patients showed type 1 electrocardiogram (ECG) at baseline. BBs and CAs were used within normal dosage range in all patients. After starting a BB and/or CA, type 1 ECG was still observed in 9 patients. There were no significant differences in the ECG parameters such as the amplitude of J-point, QRS duration, and corrected QT intervals before and after starting BB and/or CA. During follow-up of 89 ± 65 months after initiation of the drugs, 1 patient experienced a VF recurrence without significant changes of ECG parameters 2 years after BB therapy was started.

Conclusion

Long-term intake of BB or CA within normal dosage range was not associated with the aggravation of ECG parameters and clinical outcome in patients with BrS. The use of BBs and CAs is acceptable under careful observation.

Genotype-phenotype relationship and risk stratification in loss-of-function SCN5A mutation carriers

INTRODUCTION

Loss-of-function (LoF) mutations in the SCN5A gene cause multiple phenotypes including Brugada Syndrome (BrS) and a diffuse cardiac conduction defect. Markers of increased risk for sudden cardiac death (SCD) in LoF SCN5A mutation carriers are ill defined. We hypothesized that late potentials and fragmented QRS would be more prevalent in SCN5A mutation carriers compared to SCN5A-negative BrS patients and evaluated risk markers for SCD in SCN5A mutation carriers.

METHODS

We included all SCN5A loss-of-function mutation carriers and SCN5A-negative BrS patients from our center. A combined arrhythmic endpoint was defined as appropriate ICD shock or SCD.

RESULTS

Late potentials were more prevalent in 79 SCN5A mutation carriers compared to 39 SCN5A-negative BrS patients (66% versus 44%, p = .021), while there was no difference in the prevalence of fragmented QRS. PR interval prolongation was the only parameter that predicted the presence of a SCN5A mutation in BrS (OR 1.08; p < .001). Four SCN5A mutation carriers, of whom three did not have a diagnostic type 1 ECG either spontaneously or after provocation with a sodium channel blocker, reached the combined arrhythmic endpoint during a follow-up of 44 ± 52 months resulting in an annual incidence rate of 1.37%.

CONCLUSION

LP were more frequently observed in SCN5A mutation carriers, while fQRS was not. In SCN5A mutation carriers, the annual incidence rate of SCD was non-negligible, even in the absence of a spontaneous or induced type 1 ECG. Therefore, proper follow-up of SCN5A mutation carriers without Brugada syndrome phenotype is warranted.

Sodium channel current loss of function in induced pluripotent stem cell-derived cardiomyocytes from a Brugada syndrome patient

Brugada syndrome predisposes to sudden death due to disruption of normal cardiac ion channel function, yet our understanding of the underlying cellular mechanisms is incomplete. Commonly used heterologous expression models lack many characteristics of native cardiomyocytes and, in particular, the individual genetic background of a patient. Patient-specific induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPS-CM) may uncover cellular phenotypical characteristics not observed in heterologous models. Our objective was to determine the properties of the sodium current in iPS-CM with a mutation in SCN5A associated with Brugada syndrome. Dermal fibroblasts from a Brugada syndrome patient with a mutation in SCN5A (c.1100G>A, leading to Nav1.5_p.R367H) were reprogrammed to iPS cells. Clones were characterized and differentiated to form beating clusters and sheets. Patient and control iPS-CM were structurally indistinguishable. Sodium current properties of patient and control iPS-CM were compared. These results were contrasted with those obtained in tsA201 cells heterologously expressing sodium channels with the same mutation. Patient-derived iPS-CM showed a 33.1-45.5% reduction in INa density, a shift in both activation and inactivation voltage-dependence curves, and faster recovery from inactivation. Co-expression of wild-type and mutant channels in tsA201 cells did not compromise channel trafficking to the membrane, but resulted in a reduction of 49.8% in sodium current density without affecting any other parameters. Cardiomyocytes derived from iPS cells from a Brugada syndrome patient with a mutation in SCN5A recapitulate the loss of function of sodium channel current associated with this syndrome; including pro-arrhythmic changes in channel function not detected using conventional heterologous expression systems.

Clinical and Mechanistic Insights Into the Genetics of Cardiomyopathy

Over the last quarter-century, there has been tremendous progress in genetics research that has defined molecular causes for cardiomyopathies. More than a thousand mutations have been identified in many genes with varying ontologies, therein indicating the diverse molecules and pathways that cause hypertrophic, dilated, restrictive, and arrhythmogenic cardiomyopathies. Translation of this research to the clinic via genetic testing can precisely group affected patients according to molecular etiology, and identify individuals without evidence of disease who are at high risk for developing cardiomyopathy. These advances provide insights into the earliest manifestations of cardiomyopathy and help to define the molecular pathophysiological basis for cardiac remodeling. Although these efforts remain incomplete, new genomic technologies and analytic strategies provide unparalleled opportunities to fully explore the genetic architecture of cardiomyopathies. Such data hold the promise that mutation-specific pathophysiology will uncover novel therapeutic targets, and herald the beginning of precision therapy for cardiomyopathy patients.

The new kids on the block of arrhythmogenic disorders: Short QT syndrome and early repolarization

Short QT syndrome (SQTS) is one of the rarest inheritable cardiac channelopathies, characterized by an accelerated cardiac repolarization, which is also the substrate for the development of life-threatening ventricular arrhythmias. Up to this date, fewer than 200 SQTS cases have been reported in the literature worldwide. Patients with SQTS may experience a cardiac arrest as early as in the neonatal period or as late as 80 years old. The cumulative probability of experiencing a cardiac arrest by the fifth decade of life approaches 40%, highlighting the importance of early recognition and management. SQTS is an autosomal dominant disease with five identified causative genes, including three that encode for potassium channels (KCNH2, KCNQ1, and KCNJ2) and two that encode for subunits of the L-type calcium channels (CACNA1C and CACNB2). The term "early repolarization" (ER) has long been used to refer to a heterogeneous group of specific QRS-T junction patterns that are commonly found on the electrocardiograms of young healthy subjects. In the last decade, it has been suggested that in some individuals, the presence of ER may be associated with an increased risk of sudden cardiac death, and thus the term "early repolarization syndrome" (ERS) has progressively entered into use. Up to this point, however, whether ER constitutes a true primary arrhythmic disorder or whether it is simply a predisposing substrate that facilitates arrhythmias in the presence of other triggers remains an unresolved issue. In this review paper, we aim to integrate the current literature on SQTS and ERS. For each, we will describe the key steps that first led to the identification of the syndrome before moving into a discussion of our current understanding of each entity, including the epidemiology, genetics, diagnosis, clinical manifestations, and management.

A mutation in the CACNA1C gene leads to early repolarization syndrome with incomplete penetrance: A Chinese family study

Background

Early repolarization syndrome (ERS) may be a near-Mendelian or an oligogenic disease; however, no direct evidence has been provided to support this theory.

Methods and results

We described a large Chinese family with nocturnal sudden cardiac death induced by ERS in most of the young male adults. One missense mutation (p.Q1916R) was found in the major subunit of the L-type calcium channel gene CACNA1C by the direct sequencing of candidate genes. A concomitant gain-of-function variant in the sodium channel gene SCN5A (p.R1193Q) was found to rescue the phenotype of the female CACNA1C-Q1916R mutation carriers, which led to the incomplete penetrance. The functional studies, via the exogenous expression approach, revealed that the CACNA1C-Q1916R mutation led to a decreasing L-type calcium current and the protein expression defect. The decreased calcium current produced by the mutant channel was improved by isoproterenol but exacerbated by testosterone. The effects of CACNA1C-Q1916R mutation and testosterone on cellular electrophysiology were further confirmed by the human ventricular action potential simulation.

Conclusions

Our results demonstrated that the loss-of-function CACNA1C-Q1916R mutation contributed to ERS-related sudden cardiac death, and the phenotypic incomplete penetrance was modified by the SCN5A-R1193Q variant and sex. These findings suggest that phenotypes of ERS are modified by multiple genetic factors, which supports the theory that ERS may be an oligogenic disease.

Brugada Syndrome and Early Repolarisation: Distinct Clinical Entities or Different Phenotypes of the Same Genetic Disease?

Brugada and early repolarisation (ER) syndromes are currently considered two distinct inherited electrical disorders with overlapping clinical and electrocardiographic features. A considerable number of patients diagnosed with ER syndrome have a genetic mutation related to Brugada syndrome (BrS). Due to the high variable phenotypic manifestation, patients with BrS may present with inferolateral repolarisation abnormalities only, resembling the ER pattern. Moreover, the complex genotype-phenotype interaction in BrS can lead to the occurrence of mixed phenotypes with ER syndrome. The first part of this review focuses on specific clinical and electrocardiographic features of BrS and ER syndrome, highlighting the similarity shared by the two primary electrical disorders. The genetic background, with emphasis on the complexity of genotype-phenotype interaction, is explored in the second part of this review.

Variants in the SCN5A Promoter Associated With Various Arrhythmia Phenotypes

BACKGROUND

Mutations in the coding sequence of SCN5A, which encodes the cardiac Na(+) channel α subunit, have been associated with inherited susceptibility to various arrhythmias. Variable expression of SCN5A is a possible mechanism responsible for this pleiotropic effect; however, it is unknown whether variants in the promoter and regulatory regions of SCN5A also modulate the risk of arrhythmias.

METHODS AND RESULTS

We resequenced the core promoter region of SCN5A and the regulatory regions of SCN5A transcription in 1298 patients with arrhythmia phenotypes (atrial fibrillation, n=444; sinus node dysfunction, n=49; conduction disease, n=133; Brugada syndrome, n=583; and idiopathic ventricular fibrillation, n=89). We identified 26 novel rare variants in the SCN5A promoter in 29 patients affected by various arrhythmias (atrial fibrillation, n=6; sinus node dysfunction, n=1; conduction disease, n=3; Brugada syndrome, n=14; idiopathic ventricular fibrillation, n=5). The frequency of rare variants was higher in patients with arrhythmias than in controls. In the alignment with chromatin immunoprecipitation sequencing data, the majority of variants were located at regions bound by transcription factors. Using a luciferase reporter assay, 6 variants (Brugada syndrome, n=3; idiopathic ventricular fibrillation, n=2; conduction disease, n=1) were functionally characterized, and each displayed decreased promoter activity compared with the wild-type sequences. We also identified rare variants in the regulatory region that were associated with atrial fibrillation, and the variant decreased promoter activity.

CONCLUSIONS

Variants in the core promoter region and the transcription regulatory region of SCN5A were identified in multiple arrhythmia phenotypes, consistent with the idea that altered SCN5A transcription levels modulate susceptibility to arrhythmias.

Sudden death and cardiac arrest without phenotype: the utility of genetic testing

Approximately 4% of sudden cardiac deaths are unexplained [the sudden arrhythmic death syndrome (SADS)], and up to 6-10% of survivors of cardiac arrest do not have an identifiable cardiac abnormality after comprehensive clinical evaluation [idiopathic ventricular fibrillation (IVF)]. Genetic testing may be able to play a role in diagnostics and can be targeted to an underlying phenotype present in family members following clinical evaluation. Alternatively, post-mortem genetic testing (the "molecular autopsy") may diagnose the underlying cause if a clearly pathogenic rare variant is found. Limitations include a modest yield, and the high probability of finding a variant of unknown significance (VUS) leading to a low signal-to-noise ratio. Next generation sequencing enables cost-efficient high throughput screening of a larger number of genes but at the expense of increased genetic noise. The yield from genetic testing is even lower in IVF in the absence of any suggestion of another phenotype in the index case or his/her family, and should be actively discouraged at this time. Future improvements in diagnostic utility include optimization of the use of variant-calling pipelines and shared databases as well as patient-specific models of disease to more accurately assign pathogenicity of variants. Studying "trios" of parents and the index case may better assess the yield of sporadic and recessive disease.

Early Repolarization Syndrome; Mechanistic Theories and Clinical Correlates

The early repolarization (ER) pattern on the 12-lead electrocardiogram is characterized by J point elevation in the inferior and/or lateral leads. The ER pattern is associated with an increased risk of ventricular arrhythmias and sudden cardiac death (SCD). Based on studies in animal models and genetic studies, it has been proposed that J point elevation in ER is a manifestation of augmented dispersion of repolarization which creates a substrate for ventricular arrhythmia. A competing theory regarding early repolarization syndrome (ERS) proposes that the syndrome arises as a consequence of abnormal depolarization. In recent years, multiple clinical studies have described the characteristics of ER patients with VF in more detail. The majority of these studies have provided evidence to support basic science observations. However, not all clinical observations correlate with basic science findings. This review will provide an overview of basic science and genetic research in ER and correlate basic science evidence with the clinical phenotype.

Polytherapy with sodium channel-blocking antiepileptic drugs is associated with arrhythmogenic ST-T abnormality in patients with epilepsy

PURPOSE

Recent reports have documented the appearance of Brugada-type ST elevation in cases of overdose of antiepileptic drugs (AEDs). However, little is known about changes on electrocardiographs (ECGs) during AED use at therapeutic doses. AEDs may cause Brugada-type ST elevation or J-wave-like intraventricular conduction delays through an ion channel-blocking effect. In the present study, we sought to elucidate ECG abnormalities in patients on AED therapy.

METHODS

The study population consisted of 120 consecutive patients with epilepsy who continued to take AEDs and had ECGs recorded during these therapies. Their clinical background and ECGs were retrospectively analyzed. Brugada-type ST elevation was classified according to the consensus report on Brugada syndrome. A J-wave-like ECG abnormality was defined as the appearance of notching or slurring of the QRS complex (>0.1mV) in the inferior/lateral leads.

RESULTS

Of the 120 patients, 15 (12.5%) exhibited Brugada-type ST elevation and 35 (29.2%) showed a J-wave-like ECG abnormality. Polytherapy with sodium channel-blocking AEDs (e.g., carbamazepine, phenytoin, lamotrigine) was more frequently observed in patients with Brugada-type ST elevation (p=0.048). However, the serum concentrations of these medicines did not differ between patients with and without ECG abnormalities (carbamazepine: 7.9±4.1 vs. 7.2±5.9μg/dL; phenytoin: 12.7±4.1 vs. 15.5±9.5μg/dL, NS).

CONCLUSION

ST-T abnormalities were frequently seen in patients using AEDs. The presence of Brugada-type ST elevation was associated with polytherapy with sodium channel-blocking AEDs.