Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report

Assessment of activation delay in the right ventricular outflow tract as a potential complementary diagnostic tool for Brugada Syndrome

AIMS

In patients with Brugada syndrome (BrS), diagnosis relies primarily on the presence of the characteristic type 1 electrocardiographic (ECG) pattern. The aim of this study was to propose an alternative diagnostic method in situations where ECG alone is uncertain.

METHODS AND RESULTS

This study was conducted in two phases: (i) Phase 1: cut-off determination. Controls and BrS patients were analysed to develop a predictive model based on electrocardiographic imaging (ECGi) parameters for the diagnosis of BrS. Patients with right bundle branch block (RBBB) were analysed separately. All patients underwent ajmaline infusion. Concealed BrS patients were evaluated in both the absence and presence of a type 1 ECG pattern. The right and left ventricular 'epicardium' maps obtained with ECGi were divided into eight regions, and the mean activation time (ATm) was calculated for each region. The ATm for each area was normalized to QRS length (ATm%); ATm and ATm% were compared across populations. (ii) Phase 2: cut-off validations. A new cohort of control and BrS patients was used to perform a blinded validation of the proposed method. In Phase 1 (cut-off determination), 57 patients affected by BrS, and 10 controls were included. Analysis of ATm and ATm% in right ventricular outflow tract (RVOT) showed significant differences between controls and BrS patients both with either concealed or manifested Pattern 1 ECG (3 721 ± 6.23 vs. 68.33 ± 14.73 ms, P < 0.001; 37.21 ± 6.23 vs. 107.57 ± 21.16 ms, P < 0.001). The relationship between the anterior-RV and the RVOT ATm was used to develop a predictive model to identify a diagnostic threshold for BrS diagnosis. An increase of 45% in anterior-RV ATm was determined to be the optimal predictor of delayed RVOT activation in BrS patients (area under the receiver operating characteristic curve = 0.97, accuracy = 0.92, F-score = 0.95). In RBBB patients, the ATm delay cut-off was reached exclusively in cases with concomitant BrS. In Phase 2, 7 out of 7 control patients exhibited a percentage increase between the anterior-RV and RVOT of <45%. Among BrS patients with concealed pattern (pattern-concealed), 11 out of 20 showed a percentage increase >45% (accuracy 67%). In BrS patients with manifested Pattern 1 (pattern-positive), 19 out of 20 showed a percentage increase of >45% (accuracy 96%).

CONCLUSION

In BrS, the delay in RVOT activation can be identified using a threshold value of 45% above the mean activation time in the anterior-RV for each patient, offering a reliable diagnostic tool when standard ECG method alone falls short.

Validation and clinical implications of higher intercostal space electrocardiography in the patient with Brugada syndrome in Taiwan (SADS-TW BrS registry)

BACKGROUND

Diagnosis of Brugada syndrome (BrS) is based on type 1 morphology (coved type) in electrocardiograms from standard (4th) or higher (2nd or 3rd) intercostal spaces (ICSs). However, the clinical implications of being diagnosed only at higher ICSs remains poorly understood. We aimed to investigate the diagnostic accuracy of higher ICS leads in the Taiwanese Brugada syndrome population and clarify if there is any difference in clinical presentation.

METHOD

Patients enrolled in the Sudden Arrhythmic Death Syndrome-Taiwan (SADS-TW) registry from 2010/01/01 to 2021/07/30 were retrospectively reviewed. Records were examined for 163 patients whose ECGs in the 2nd, 3rd, and/or 4th ICSs showed a type 1 BrS pattern in at least 1 lead. Baseline characteristics, family history, clinical presentation, SCN5A mutation status, cardiovascular events, and mortality were analyzed.

RESULT

Using the standard ICS alone, 56.4% patients could be diagnosed with BrS, whereas the remaining 43.6% of patients could only be diagnosed using higher ICSs. The mean age of diagnosis using higher ICSs was 42.2 ± 14.7 years vs. 46.8 ± 14.6 years in patients diagnosed using the standard ICSs (p = 0.048). Hypertension was more prevalent in patients diagnosed by standard ICSs (27.2%) vs. patients diagnosed by higher ICSs (4.2%; p < 0.001). No differences were observed in family history, clinical presentation, SCN5A mutation status, cardiovascular events, or mortality (mean follow-up time = 3.96 ± 3.45 years, p = 0.28).

CONCLUSION

Using higher intercostal leads could significantly increase the diagnosis rate of BrS in the Taiwanese population, although it would not affect the clinical prognosis.

Brugada Syndrome in Sports Cardiology: An Expert Opinion Statement of the Italian Society of Sports Cardiology (SICSport)

Brugada syndrome (BrS) is a genetic disorder marked by a characteristic electrocardiogram (ECG) pattern of ST-segment elevation and T-wave inversion in right precordial leads, which is associated with an increased risk of ventricular fibrillation in the absence of structural heart disease. Despite advancements in understanding its epidemiology, pathophysiology, and treatment, there is considerable variability in how sports cardiologists approach BrS. This expert opinion by the Italian Society of Sports Cardiology (SICSPORT) aim to review the current definition, diagnosis, epidemiology, genetics, risk stratification, and treatment of BrS and provide guidance for sport eligibility provides guidance for sports doctors and cardiologists in assessing competitive sports eligibility in athletes with BrS. A multiparametric approach to diagnosis and risk stratification is recommended, noting that the presence of a Brugada ECG pattern (BrP) does not confirm a BrS diagnosis. The risk of sudden cardiac death (SCD) is low in asymptomatic individuals with type 1 BrP, especially those with a drug-induced pattern. Pharmacological testing is not required for type 2 or 3 patterns without other risk factors. Low-risk individuals do not require therapy, while intermediate or high-risk patients may need pharmacological treatment, ICD implantation, or ablation. Asymptomatic individuals with type 2 or 3 BrP, no family history of SCD, and no other risk factors may be eligible for competitive sports, as well as asymptomatic type 1 BrP without risk factors and negative electrophysiological study. Conversely, sports eligibility should be denied in patients with BrS who have a history of syncope or cardiac arrest (high-risk subjects), regardless of ICD presence.

Eighteen-year analysis of anaesthetic management in Brugada syndrome: The BRUGANAES study

BACKGROUND

Brugada syndrome (BrS) is a genetic disorder that increases the risk of ventricular tachyarrhythmias and sudden cardiac death (SCD). Certain drugs (propofol, local anaesthetics), fever, bradycardia, increased vagal tone and electrolyte imbalances can trigger or worsen BrS arrhythmias.

OBJECTIVE

To evaluate the incidence of malignant ventricular arrhythmias during the perioperative period in patients with BrS, hypothesising that common anaesthetic drugs may be safe to use during daily clinical practice.

DESIGN

The BRUGANAES study was an observational, retrospective project including BrS patients who underwent various types of anaesthesia.

SETTING

BrS patients undergoing any type of anaesthesia intervention from 1 January 2006, to 31 December 2023, from a tertiary hospital in Barcelona.

MAIN OUTCOME MEASURES

The primary outcome was the occurrence of malignant ventricular arrhythmias and/or SCD during and up to 30 days postanaesthesia. Secondary outcomes included adverse events during hospitalisation, 30-day readmission rates and 30-day mortality rates.

RESULTS

Among 652 BrS patients registered in the hospital, 111 patients and 189 procedures were analysed. General anaesthesia was administered in 51.3% of cases, sedation in 36% and regional/neuraxial anaesthesia exclusively in 12.7%. Overall, nonrecommended drugs (propofol, ketamine and local anaesthetics) were used in 129 (68.3%) procedures, either bolus and/or continuous infusion. Epidural blocks were performed in 34% of regional anaesthesia cases, mostly in obstetrics, and subarachnoid blocks in 31.8%. The primary outcome occurred in two patients intraoperatively (1% of procedures): one with bradycardia-induced ventricular fibrillation after a nonrecommended drug and one with transient ventricular tachycardia after a drug not listed as potentially harmful.

CONCLUSION

To date, this is one of the largest cohorts describing the perioperative approach for BrS patients, including a wide range of anaesthesia procedures and drugs. Most of the patients undergoing anaesthesia for an interventional procedure received an anaesthetic drug classified as not recommended.

Anesthetic management in patients with long QT and Brugada syndromes

PURPOSE OF REVIEW

Both long QT and Brugada syndrome are inherited arrhythmic conditions that can predispose patients to life-threatening ventricular arrhythmias. Managing the anesthesia for patients with either long QT or Brugada syndrome necessitates an understanding of potential drug-drug interactions with the underlying channelopathy. This review illustrates contemporary insight into managing such patients for the anesthesiologist.

RECENT FINDINGS

Long QT, due to disorder of potassium or sodium ion channels, is associated with prolonged repolarization of the action potential phase. Medications that prolong the action potential should be avoided. In patients with long QT syndrome, each drug administered should be carefully reviewed to be certain it does not prolong the QT interval. Brugada syndrome is a result of a pathogenic sodium channel that results in potential ventricular arrhythmias. Medications that exacerbate the electrocardiographic changes of Brugada should be avoided.

SUMMARY

Anesthesiologists need to be aware of proper management in children with known or suspected long QT or Brugada pathologies as well as the potential poly-pharmaceutical impact that exists on cardiac ion channels.

Implantable Cardioverter-Defibrillator Therapy in Brugada Syndrome: A 30-Year Single-Center Experience

BACKGROUND

Brugada syndrome (BrS) continues to pose clinical challenges, despite 3 decades of dedicated research and therapeutic advancements. The pivotal role of implantable cardioverter-defibrillator (ICD) therapy in safeguarding high-risk BrS patients from sudden cardiac death due to ventricular arrhythmias is undeniable. However, the debate on risk stratification and the use of ICDs for primary prevention remains ongoing.

OBJECTIVES

This study aimed to evaluate the clinical features, management, and long-term outcomes of ICD therapy in patients with Brugada syndrome.

METHODS

BrS-diagnosed patients were prospectively enrolled. Inclusion criteria were: 1) a Brugada type 1 electrocardiogram pattern, either spontaneous or drug induced; 2) ICD implantation; and 3) consistent follow-up. Risk stratification was based on prior arrhythmic events, and the multiparametric Brussel risk score was used from 2017. High-risk patients underwent video-thoracoscopic epicardial ablation starting in 2016. ICD implantation strategies evolved over time, guided by patients' clinical and demographic characteristics.

RESULTS

A total of 306 consecutive Brugada patients (186 male [61%]; mean age 41 ± 17 years; range: 1-82 years) received ICDs at our institution from 1992 to 2022. ICDs were implanted for secondary prevention in 16% of patients. Over the 3 decades, the proportions of secondary prevention implants and asymptomatic patients remained stable, while risk factors fluctuated in the first two decades before stabilizing. During long-term follow-up (median 103 months [63-147 months]), 14% of patients experienced at least 1 sustained ventricular arrhythmia (VA) (1.59 per 100 person-years), 15% had at least 1 inappropriate ICD shock-unaffected by the presence of single or dual leads-and 27% required device revision and/or lead replacement. Patients with secondary prevention ICDs had a higher incidence of both ventricular and supraventricular arrhythmias compared to those with primary prevention ICDs. Loss-of-function mutations and prior nonsustained VAs were associated with sustained VAs. Among high-risk patients, those who underwent epicardial ablation experienced significantly fewer ventricular events. The overall mortality rate was 5.88%, with 22.2% of deaths attributed to cardiac causes.

CONCLUSIONS

This 30-year study highlights ICD therapy's critical role in preventing fatal arrhythmias in Brugada syndrome, but also reveals frequent device-related complications, especially in younger patients. Thoracoscopic epicardial ablation significantly reduced VA in high-risk patients, offering a promising adjunctive therapy. These findings emphasize the need for individualized treatment strategies to balance the benefits of ICDs with their risks, and underscore the potential of ablation to improve long-term outcomes.

A new hypothesis to explain disease dominance

The onset and progression of dominant diseases are thought to result from haploinsufficiency or dominant negative effects. Here, we propose transcriptional adaptation (TA), a newly identified response to mRNA decay, as an additional cause of some dominant diseases. TA modulates the expression of so-called adapting genes, likely via mRNA decay products, resulting in genetic compensation or a worsening of the phenotype. Recent studies have challenged the current concepts of haploinsufficiency or poison proteins as the mechanisms underlying certain dominant diseases, including Brugada syndrome, hypertrophic cardiomyopathy, and frontotemporal lobar degeneration. We hypothesize that for these and other dominant diseases, when the underlying mutation leads to mRNA decay, the phenotype is due at least partly to the dysregulation of gene expression via TA.

Artificial intelligence for Brugada syndrome diagnosis and gene variants interpretation

Brugada Syndrome (BrS) is a hereditary cardiac condition associated with an elevated risk of lethal arrhythmias, making precise and prompt diagnosis vital to prevent life-threatening outcomes. The diagnosis of BrS is challenging due to the requirement of invasive drug challenge tests, limited human visual capacity to detect subtle electrocardiogram (ECG) patterns, and the transient nature of the disease. Artificial intelligence (AI) can detect almost all patterns of BrS in ECG, some of which are even beyond the capability of expert eyes. AI is subcategorized into several models, with deep learning being considered the most beneficial, boasting its highest accuracy among the other models. With the capability to discriminate subtle data and analyze extensive datasets, AI has achieved higher accuracy, sensitivity, and specificity compared to trained cardiologists. Meanwhile, AI proficiency in managing complex data enables us to discover unclassified genetic variants. AI can also analyze data extracted from induced pluripotent stem cell-derived cardiomyocytes to distinguish BrS from other inherited cardiac arrhythmias. The aim of this study is to present a synopsis of the evolution of various algorithms of artificial intelligence utilized in the diagnosis of BrS and compare their diagnostic abilities to trained cardiologists. In addition, the application of AI for classification of BrS gene variants is also briefly discussed.

SCN5A variant type-dependent risk prediction in Brugada syndrome

AIMS

The variant in SCN5A with the loss of function (LOF) effect in the cardiac Na+ channel (Nav1.5) is the definitive cause for Brugada syndrome (BrS), and the functional analysis data revealed that LOF variants are associated with poor prognosis. However, which variant types (e.g. missense or non-missense) affect the prognoses of those variant carriers remain unelucidated.

METHODS AND RESULTS

We defined SCN5A LOF variants as all non-missense and missense variants that produce peak INa < 65% of wild-type previously confirmed by patch-clamp studies. The study population consisted of 76 Japanese BrS patients (74% patients were male and the median age [IQR] at diagnosis was 28 [14-45] years) with LOF type of SCN5A variants: 40 with missense and 36 with non-missense variants. Non-missense variant carriers presented significantly more severe cardiac conduction disorder compared to the missense variant carriers. During follow-up periods of 9.0 [5.0-14.0] years, compared to missense variants, non-missense variants were significant risk factors of lifetime lethal arrhythmia events (LAEs) (P = 0.023). When focusing only on the missense variants that produce no peak INa, these missense variant carriers exhibited the same clinical outcomes as those with non-missense (log-rank P = 0.325). After diagnosis, however, both variant types were comparable in risk of LAEs (P = 0.155).

CONCLUSION

We identified, for the first time, that SCN5A non-missense variants were associated with higher probability of LAE than missense variants in BrS patients though it did not change significantly after diagnosis.

Spontaneous type 1 ECG and arrhythmic risk in Brugada syndrome: A meta-analysis of adjusted time-to-event data

Background

Brugada syndrome (BrS) is associated with an increased risk of major arrhythmic events (MAEs), particularly in patients with a spontaneous type 1 electrocardiographic (ECG) pattern.

Objective

Because previous meta-analyses used mainly crude or unadjusted data from observational studies, we conducted an updated meta-analysis on the prognostic role of spontaneous type 1 ECG in BrS patients combining adjusted and unadjusted data separately.

Methods

We conducted a systematic search of PubMed and Cochrane Central Register of Controlled Trials from inception to May 2024. Studies providing hazard ratios for MAEs associated with spontaneous type 1 ECG in BrS patients were included.

Results

Eighteen studies comprising 7238 patients were included, with 10 providing adjusted and 17 providing unadjusted data. Separate pooled analyses using a random-effects model demonstrated a significantly increased risk of MAEs in BrS patients with spontaneous type 1 ECG compared with those without, with a pooled adjusted hazard ratio (aHR) of 2.05 (95% CI 1.38-3.03) and an unadjusted hazard ratio of 2.97 (95% CI 2.04-4.34). Subgroup analysis revealed higher risks in studies with non-Asian populations and those including patients with no history of aborted cardiac arrest (aHR 2.36, 95% CI 1.35-4.11; and aHR 3.56, 95% CI 2.35-5.41, respectively) and a persistent significant risk in studies accounting for syncope as a covariate (aHR 2.01, 95% CI 1.24-3.27).

Conclusion

Our analysis indicates that patients with BrS and spontaneous type 1 ECG are at higher risk of MAEs. This is consistent across various subgroups, including asymptomatic individuals.

A Vision Transformer Model for the Prediction of Fatal Arrhythmic Events in Patients with Brugada Syndrome

Brugada syndrome (BrS) is an inherited electrical cardiac disorder that is associated with a higher risk of ventricular fibrillation (VF) and sudden cardiac death (SCD) in patients without structural heart disease. The diagnosis is based on the documentation of the typical pattern in the electrocardiogram (ECG) characterized by a J-point elevation of ≥2 mm, coved-type ST-segment elevation, and negative T wave in one or more right precordial leads, called type 1 Brugada ECG. Risk stratification is particularly difficult in asymptomatic cases. Patients who have experienced documented VF are generally recommended to receive an implantable cardioverter defibrillator to lower the likelihood of sudden death due to recurrent episodes. However, for asymptomatic individuals, the most appropriate course of action remains uncertain. Accurate risk prediction is critical to avoiding premature deaths and unnecessary treatments. Due to the challenges associated with experimental research on human cardiac tissue, alternative techniques such as computational modeling and deep learning-based artificial intelligence (AI) are becoming increasingly important. This study introduces a vision transformer (ViT) model that leverages 12-lead ECG images to predict potentially fatal arrhythmic events in BrS patients. This dataset includes a total of 278 ECGs, belonging to 210 patients which have been diagnosed with Brugada syndrome, and it is split into two classes: event and no event. The event class contains 94 ECGs of patients with documented ventricular tachycardia, ventricular fibrillation, or sudden cardiac death, while the no event class is composed of 184 ECGs used as the control group. At first, the ViT is trained on a balanced dataset, achieving satisfactory results (89% accuracy, 94% specificity, 84% sensitivity, and 89% F1-score). Then, the discarded no event ECGs are attached to additional 30 event ECGs, extracted by a 24 h recording of a singular individual, composing a new test set. Finally, the use of an optimized classification threshold improves the predictions on an unbalanced set of data (74% accuracy, 95% negative predictive value, and 90% sensitivity), suggesting that the ECG signal can reveal key information for the risk stratification of patients with Brugada syndrome.

A Rare Noncoding Enhancer Variant in SCN5A Contributes to the High Prevalence of Brugada Syndrome in Thailand

BACKGROUND

Brugada syndrome (BrS) is a cardiac arrhythmia disorder that causes sudden death in young adults. Rare genetic variants in the SCN5A gene encoding the Nav1.5 sodium channel and common noncoding variants at this locus are robustly associated with the condition. BrS is particularly prevalent in Southeast Asia but the underlying ancestry-specific factors remain largely unknown.

METHODS

Genome sequencing of BrS probands and population-matched controls from Thailand was performed to identify rare noncoding variants at the SCN5A-SCN10A locus that were enriched in patients with BrS. A likely causal variant was prioritized by computational methods and introduced into human induced pluripotent stem cell (hiPSC) lines using CRISPR-Cas9. The effect of the variant on SCN5A expression and Nav1.5 sodium channel current was then assessed in hiPSC-derived cardiomyocytes (hiPSC-CMs).

RESULTS

A rare noncoding variant in an SCN5A intronic enhancer region was highly enriched in patients with BrS (detected in 3.9% of cases with a case-control odds ratio of 45.2). The variant affects a nucleotide conserved across all mammalian species and predicted to disrupt a Mef2 transcription factor binding site. Heterozygous introduction of the enhancer variant in hiPSC-CMs caused significantly reduced SCN5A expression from the variant-containing allele and a 30% reduction in Nav1.5-mediated sodium current density compared with isogenic controls, confirming its pathogenicity. Patients with the variant had severe phenotypes, with 89% experiencing cardiac arrest.

CONCLUSIONS

This is the first example of a functionally validated rare noncoding variant at the SCN5A locus and highlights how genome sequencing in understudied populations can identify novel disease mechanisms. The variant partly explains the increased prevalence of BrS in this region and enables the identification of at-risk variant carriers to reduce the burden of sudden cardiac death in Thailand.

Genetic background and clinical phenotype in a Vietnamese cohort with Brugada syndrome: A whole exome sequencing study

Objectives

The aim of this study was to report the spectrum of genetic variations and clinical phenotype in a Vietnamese cohort with confirmed Brugada syndrome (BrS) using the whole exome sequencing (WES).

Methods

Fifty patients with confirmed BrS were included in this study. Genomic DNA samples were extracted from peripheral blood and conducted for WES. The variants were annotated using ANNOVAR. The variants in the 13 reported genes associated with BrS were filtered, predicted the functional impact using eight computational tools, and classified according to the 2015 ACMG guidelines.

Results

Arrhythmic events were documented in one-fifth of the participants. Twenty-four probands were identified to carry 36 variants in 13 genes. Majority of the variants in our study was SCN5A variants (9/36 variants, 25%), followed by KCNH2 variants (5/36 variants, 14%). The prevalence of SCN5A carriers was 16%; while the prevalence of minor gene carriers was less than 10%. Nine novel missense variants were identified, including four missense SCN5A variants (p.E901D, p.F853L, p.L377F, and p.H184R), two missense ANK2 variants (p.S2845L and V1497L), one missense CACNA1C variant (M1126V), one missense DSP variant (p.K478N), and one intron splicing JUP variant (c.1498-5G>C).

Conclusion

Our study underscores the primary significance of the SCN5A gene in BrS, as indicated by variant prevalence, carrier rates, pathogenicity per ACMG classification, in silico predictions, and its correlation with clinical phenotypes. Longitudinal study with larger sample size, pedigree, Sanger sequence confirmation, and functional analysis is recommended.

Transcriptomic Profiling of Human Myocardium at Sudden Death to Define Vulnerable Substrate for Lethal Arrhythmias

BACKGROUND

While some chronic pathological substrates for sudden cardiac death (SCD) are well known (eg, coronary artery disease and left ventricular [LV] dysfunction), the acute vulnerable myocardial state predisposing to fatal arrhythmia remains a critical barrier to near-term SCD prevention.

OBJECTIVES

This study sought to define the distinct myocardial transcriptomic profile of autopsy-defined arrhythmic sudden deaths, compared to nonarrhythmic sudden deaths and trauma deaths, to determine the acute vulnerable state in the hours to days before SCD.

METHODS

We used autopsy to adjudicate arrhythmic from nonarrhythmic causes in 1,265 sudden deaths in San Francisco County from 2011 to 2018. We performed a degradation-tolerant transcriptomic evaluation of LVs sampled at the time of SCD from 245 consented cases using a curated panel of 448 gene probes with known or hypothesized association with SCD.

RESULTS

The targeted transcriptome of arrhythmic (n = 129) vs nonarrhythmic (n = 90 nonarrhythmic sudden deaths + 26 trauma deaths) LV samples revealed 31 differentially up-regulated and 36 down-regulated genes (adjusted P < 0.05) related to the collagen-containing extracellular matrix (up-regulation of FAP, FMOD, and LTBP2), regulation of ion transport (up-regulation of KCNA5 and KCNN3 and down-regulation of KCNJ8, KCNK1, and KCNJ5), and contraction (down-regulation of MYH6). Fibrosis-related genes showed the highest magnitude increased expression in arrhythmic vs nonarrhythmic deaths and vs published transcriptomes from end-stage heart failure. After molecular stratification by known markers for mature (COL1A1, COL1A2, COL3A1) and active (POSTN, MEOX1) fibrosis, cases with the highest expression of both had the largest proportion of arrhythmic cause of death (n = 27 of 36 [75%]) vs cases with low expression of both markers (n = 87 of 181 [38%]) (P = 0.006) or vs mature only (n = 10 of 14 [71%]) or active only (n = 5 of 14 [36%]). Activated fibroblast gene expression signature was enriched in arrhythmic female vs arrhythmic male cases, among other sex-specific differences in ion-channel and myosin (up-regulation of SCN4B, SCN8A, and KCNAB1 in females and KCNJ4 and MYH7B in males) expression.

CONCLUSIONS

RNA profiling of the myocardium at SCD identifies active fibrosis, undetectable by conventional clinical methods, in the presence of fixed scar and selected ion-channel dysregulation (more pronounced among female cases) as an acute vulnerable substrate for fatal arrhythmias. These findings may represent novel directions to identify patients at elevated near-term risk for SCD and critical pathways for intervention to reduce acute lethal arrhythmias.

Appropriate implantable cardioverter-defibrillator therapy triggered by heat stroke

We present a case of a 20 years old male with a history of syncope and Brugada type 1 pattern confirmed by a pharmacological test with flecainide, inducible ventricular tachycardia on an electrophysiological study, and had undergone placement of implantable cardioverter-defibrillator (ICD). In 12 months of follow-up, the patient was asymptomatic; on a day of extreme heat (46°C), he had a presyncope episode followed by an ICD shock. The patient was brought to the emergency room with heat stroke symptoms. ECG showed a Brugada type 1 pattern, and ICD interrogation showed ventricular fibrillation followed by successful conversion with 36-joules shock. Physical methods were used to lower body temperature in addition to intravenous fluids infusion. The patient was stabilized and discharged after 48 hrs.

Automatized quantitative electrocardiography from digitized paper electrocardiograms: A new avenue for risk stratification in patients with Brugada syndrome

BACKGROUND

Arrhythmic risk stratification is a major challenge in Brugada syndrome. Studies have evaluated risk stratification based on manually measured electrocardiogram (ECG) parameters at baseline and/or after drug challenge.

AIM

To assess the predictive value of multiple ECG parameters measured automatically from digitized paper ECGs.

METHODS

During a prospective, multicentre cohort study that included patients with Brugada syndrome with type 1 ECG (spontaneously or drug-induced), paper ECGs were digitized and analysed. Major events were sudden cardiac death, aborted cardiac arrest and appropriate implantable cardioverter-defibrillator (ICD) therapy in the ventricular fibrillation (VF) zone. The predictive value of clinical and ECG parameters was assessed using univariable and multivariable Cox models.

RESULTS

ECGs from 301 patients (74% male, mean age 43.1±13.3years, mean follow-up 7.1±5.6years) were analysed. Major events occurred in 6% of patients before diagnosis and 8% during follow-up. Two baseline ECG parameters were independently associated with major events: QRS prolongation in lead V1>113ms (hazard ratio [HR] 3.49, 95% confidence interval [CI] 1.72-7.09; P<0.001) and S duration on DI>33.5ms (HR 3.56, 95% CI 1.52-8.31; P<0.01). In drug-induced patients, changes in the Tpeak-Tend interval on V2 were associated with major events (HR 4.69, 95% CI 1.21-18.17; P=0.014).

CONCLUSION

Paper ECG datasets could be used for automatic quantitative ECG measurements. We confirmed the association of previously described parameters with events and identified useful new parameters. Multi-parametric ECG quantification may be used to assess risk in patients with Brugada syndrome.

High Glucose Sensitizes Male and Female Rat Cardiomyocytes to Wnt/β-Catenin Signaling

Wnt/β-catenin signaling has been shown to regulate gene expressions in cardiomyocytes. However, it is not known if this effect is dependent on the sex of cells or the glucose level in the culture medium. In the present study, ventricular myocytes were prepared from male and female neonatal rats and maintained in either a glucose-rich (25 mM) medium or a low-glucose (3 mM), lipid-rich medium. Real-time quantitative PCR was used to measure changes in target genes (Axin2, Scn5a, and Tbx3) after treatment with 1, 3, or 10 µM of CHIR-99021, an activator of Wnt/β-catenin signaling. CHIR induced similar changes in Axin2, Tbx3, and Scn5a transcripts in male and female NRVMs in both media, suggesting the absence of sex difference. However, cells in a high-glucose medium showed greater increases in Axin2 and Tbx3 transcripts than cells in a low-glucose medium. In addition, a low concentration of CHIR (1 µM) reduced the Scn5a transcript in cells in a high-glucose medium but not in a low-glucose medium, suggesting an increased sensitivity to Wnt signaling by high glucose. A non-linear relationship was identified between Axin2 transcript upregulation and Scn5a transcript downregulation in CIHR-treated NRVMs. These data suggest that high glucose sensitizes both male and female cardiomyocytes to Wnt/β-catenin signaling.

In Vivo Mapping of Human Ventricular Fibrillation in Brugada Syndrome: The Role of Repolarization Heterogeneity

BACKGROUND

Brugada syndrome (BrS) is associated with ventricular fibrillation (VF). Different VF mechanisms have been described, and repolarization gradients were associated with VF in a BrS model. The aim of this study is to map VF in BrS with ECG imaging. Furthermore, spatial correlation between sinus rhythm maps and VF maps was evaluated.

METHODS

Inclusion criteria were (1) BrS diagnosis and (2) VF mapped with ECG imaging during right ventricle outflow tract ablation. VF mechanism was classified into (1) rotational, (2) focal, and (3) irregular. For comparison, 6 controls were enrolled. The following sinus rhythm maps were performed: activation, recovery time, and activation-recovery interval time. Spatial overlap between steep repolarization gradients (cliffs) at recovery time and activation-recovery interval time maps and initiating VF rotational activity was evaluated with photogrammetry.

RESULTS

A total of 28 VF maps in 21 patients with BrS were analyzed. In the first ≈7 seconds of VF, rotational, focal, and irregular mechanisms were found. In 19 patients with BrS (90.5%) and none of the controls, a right ventricle outflow tract repolarization cliff only was found. In all these patients, the singularity point of the first initiating rotational VF activity spatially overlapped with the right ventricle outflow tract cliff. Abolition of right ventricle outflow tract repolarization cliffs was confirmed in all but 2 patients (94.3%). In one patient with recurrence, VF was mapped on the anterior right ventricle over a cliff that was not targeted at the first ablation procedure.

CONCLUSIONS

In patients with BrS, repolarization heterogeneity has a critical role in VF. Repolarization cliffs might be a therapeutic target in VF ablation.

Intracellular calcium dysregulation in heart and brain diseases: Insights from induced pluripotent stem cell studies

The central nervous system (CNS) plays a role in regulating heart rate and myocardial contractility through sympathetic and parasympathetic nerves, and the heart can impact the functional equilibrium of the CNS through feedback signals. Although heart and brain diseases often coexist and mutually influence each other, the potential links between heart and brain diseases remain unclear due to a lack of reliable models of these relationships. Induced pluripotent stem cells (iPSCs), which can differentiate into multiple functional cell types, stem cell biology and regenerative medicine may offer tools to clarify the mechanisms of these relationships and facilitate screening of effective therapeutic agents. Because calcium ions play essential roles in regulating both the cardiovascular and nervous systems, this review addresses how recent iPSC disease models reveal how dysregulation of intracellular calcium might be a common pathological factor underlying the relationships between heart and brain diseases.

Nonmodifiable Risk Factors Predict Outcomes in Brugada Syndrome

BACKGROUND

Risk stratification in Brugada syndrome (BrS) is based on the occurrence of dynamic factors, such as unexplained syncope and documentation of spontaneous type 1 pattern. At odds with other channelopathies, the role of nonmodifiable risk factors such as sex or genetics remains uncertain.

OBJECTIVES

This study aims to identify nonmodifiable risk factors for the occurrence of life-threatening arrhythmic events (LAEs) and define their clinical utility.

METHODS

Clinical and genetic data from consecutive, unrelated Italian patients with Brugada syndrome screened on the sodium voltage-gated channel alpha subunit 5 (SCN5A) gene and 3 pivotal single-nucleotide variations (formerly single-nucleotide polymorphisms) associated with BrS (rs11708996, rs10428132, and rs9388451) were analyzed using multivariable Cox proportional hazards model.

RESULTS

In 2,182 unrelated patients with BrS (81% males; median age at diagnosis: 41.6 years [Q1-Q3: 33.4-50.3 years]), male sex (HR: 3.6; 95% CI: 1.9-6.9; P = 0.0001), missense SCN5A mutations in BrS-enriched domains (HR: 2.3; 95% CI: 1.2-4.3; P = 0.008), nonmissense SCN5A mutations (HR: 3.2; 95% CI: 1.8-5.7; P < 0.001), and polygenic risk score for BrS (HR: 1.3; 95% CI: 1.0-1.6; P = 0.041) were all independently associated with a significantly higher risk of a first LAE since birth. Based on these results, we derived the nonmodifiable risk of each patient with BrS, and the division of nonmodifiable risk into tertiles identified 3 distinct risk profiles. In an analysis at follow-up, nonmodifiable risk was independently associated with LAE at follow-up (HR: 1.8; 95% CI: 1.1-2.7; P = 0.014), alongside classical predictors including: history of LAE before diagnosis (HR: 13.8; 95% CI: 8.1-23.7; P < 0.0001), history of unexplained syncope before diagnosis (HR: 4.1; 95% CI: 2.4-6.8; P < 0.0001), and spontaneous type 1 pattern at diagnosis (HR: 2.1; 95% CI: 1.2-3.8; P = 0.010). The model was internally validated, and we derived the equation permitting to calculate the granular 5-year risk of experiencing an LAE at follow-up for each patient with BrS, which may be used to facilitate clinical decision-making.

CONCLUSIONS

Our data show that male sex, type of SCN5A mutation, and polygenic risk score for BrS define the nonmodifiable risk of each patient with BrS. Nonmodifiable risk is independently associated with LAE, regardless of symptoms or pattern type.

The Role of Human-Induced Pluripotent Stem Cells in Studying Cardiac Channelopathies

Cardiac channelopathies are inherited diseases that increase the risk of sudden cardiac death. While different genes have been associated with inherited channelopathies, there are still subtypes, e.g., catecholaminergic polymorphic ventricular tachycardia and Brugada syndrome, where the genetic cause remains unknown. Various models, including animal models, heterologous expression systems, and the human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSCs-CMs) model, have been used to study the pathophysiological mechanisms of channelopathies. Recently, researchers have focused on using hiPSCs-CMs to understand the genotype-phenotype correlation and screen drugs. By combining innovative techniques such as Clustered Regularly Interspaced Short Palindromic Repeats/Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9 (CRISPR/Cas9)-mediated genome editing, and three-dimensional (3D) engineered heart tissues, we can gain new insights into the pathophysiological mechanisms of channelopathies. This approach holds promise for improving personalized drug treatment. This review highlights the role of hiPSCs-CMs in understanding the pathomechanism of Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia and how these models can be utilized for drug screening.

Catheter ablation as an adjunctive therapy to ICD implantation in Brugada Syndrome

BACKGROUND

Brugada Syndrome (BrS) is a life-threatening cardiac arrhythmia disorder associated with an increased risk of ventricular arrhythmias (VAs) and sudden cardiac death. Current management primarily relies on implantable cardioverter-defibrillators (ICDs), but patients may experience ICD shocks. Catheter ablation (CA) has emerged as a potential intervention to target the arrhythmogenic substrate. This systematic review aims to evaluate the safety and efficacy of CA in BrS patients.

METHODS AND RESULTS

Studies with BrS patients undergoing CA for VAs were included. Fourteen studies that involved a total population of 709 BrS patients, with CA performed in 528 of them, were included. CA resulted in the non-inducibility of VAs in 91% (95% CI: 83-99, I2 = 76%) and resolution of type 1 ECG Brugada pattern in 88% (95% CI: 81-96.2, I2 = 91%) of the patients. After a mean follow-up of 30.7 months, 87% (95% CI: 80-94, I2 = 82%) of patients remained free from VAs. The incidence of VAs during follow-up was significantly lower in the ablation cohort in comparison to the group receiving only ICD therapy (OR = 0.03, 95% CI: 0.01-0.12, I2 = 0%).

CONCLUSION

CA shows potential as a therapeutic approach to reduce VAs and improve outcomes in BrS patients. While further research with a long follow-up period is required to confirm these findings, it represents a valuable tool as an add-on intervention to ICD implantation in BrS patients with a high burden of VAs.

Novel real-time automation of combined frequency and low voltage substrate mapping to guide ablation for Brugada syndrome: a case report

Background

Brugada syndrome (BrS) is an inherited cardiac condition that increases the risk of sudden cardiac death (SCD) due to ventricular arrhythmias. Catheter ablation has been shown to effectively reduce recurrent ventricular fibrillation (VF) episodes through targeting of abnormal electrograms predominantly located within the anterior surface of the right ventricular outflow tract. Signal frequency mapping is an emerging concept that provides further definition of pathological ventricular substrate.

Case summary

A 66-year-old male with BrS was admitted to our institution with implantable cardioverter defibrillator shocks for VF. Electro-anatomical mapping (EAM) and ablation were performed utilizing a novel automated frequency-based strategy. Combined automated frequency and low voltage maps were generated to define high frequency, low voltage (HF-LVo) depolarization abnormalities within the QRS complex. Low frequency, low voltage (LF-LVo) regions from the QRS terminal notch to the T-wave offset were also identified. The combined HF-LVo and LF-LVo map areas totalled 12.4 cm2, compared to the conventional low voltage and late potential map areas, which were 44 cm2 and 27.8 cm2, respectively. The ablation strategy targeted HF-LVo and LF-LVo regions only. Following ablation, re-mapping demonstrated near complete abolition of HF-LVo and LF-LVo regions, with no inducible ventricular arrhythmias during extra-stimulation testing. During follow-up, ECG normalization was observed, with no further ventricular arrhythmias and a negative ajmaline challenge at 6 months.

Discussion

Catheter ablation for BrS utilizing a novel automated combined frequency and low voltage EAM approach can objectively identify relevant substrate. The results demonstrate adequate substrate modification with comparable ablation target areas to previous studies and encouraging clinical outcomes.

A change in QT interval and ST-segment after radiofrequency catheter ablation in pediatric patients with Wolff-Parkinson-White syndrome

BACKGROUND

Few studies have examined QT, JT interval, and ST-segment changes due to radiofrequency catheter ablation (RFA) in manifest Wolff-Parkinson-White (WPW) syndrome in pediatric patients.

METHODS

The study involved 27 patients (male-to-female, 13:14; age, 12 (5-16) years) who were diagnosed with WPW syndrome and underwent RFA in our hospital between 2009 and 2022. Electrocardiographic (ECG) changes were compared between the group with ventricular preexcitation due to an accessory pathway (manifest group, n = 16) and those without it (concealed group, n = 11).

RESULTS

The QT interval before RFA was significantly longer in the manifest group than in the concealed group (402 [362-482] vs. 344 [323-427]; p = 0.001). The QT interval was significantly shortened in the manifest group before and after RFA (402 [362-482] vs. 360 [298-422] msec; p = 0.01). At 1 month, the QT interval difference between the manifest and concealed groups disappeared (366 [305-437] vs. 335 [301-436] msec; p = 0.001). ST-segment changes were found after RFA in 56 % (9/16) of the patients in the manifest group but not in the concealed group. ECG changes presenting the Brugada-pattern was found in one patient. One month later, ECG abnormalities persisted in only one patient.

CONCLUSIONS

In pediatric patients, the QT interval was prolonged in manifest WPW syndrome but shortened after RFA. In the manifest group, transient ST-segment change and T-wave abnormalities were often observed after RFA; however, the ECG normalized in approximately 1 month.

NaV1.5 autoantibodies in Brugada syndrome: pathogenetic implications

BACKGROUND AND AIMS

Patients suffering from Brugada syndrome (BrS) are predisposed to life-threatening cardiac arrhythmias. Diagnosis is challenging due to the elusive electrocardiographic (ECG) signature that often requires unconventional ECG lead placement and drug challenges to be detected. Although NaV1.5 sodium channel dysfunction is a recognized pathophysiological mechanism in BrS, only 25% of patients have detectable SCN5A variants. Given the emerging role of autoimmunity in cardiac ion channel function, this study explores the presence and potential impact of anti-NaV1.5 autoantibodies in BrS patients.

METHODS

Using engineered HEK293A cells expressing recombinant NaV1.5 protein, plasma from 50 BrS patients and 50 controls was screened for anti-NaV1.5 autoantibodies via western blot, with specificity confirmed by immunoprecipitation and immunofluorescence. The impact of these autoantibodies on sodium current density and their pathophysiological effects were assessed in cellular models and through plasma injection in wild-type mice.

RESULTS

Anti-NaV1.5 autoantibodies were detected in 90% of BrS patients vs. 6% of controls, yielding a diagnostic area under the curve of .92, with 94% specificity and 90% sensitivity. These findings were consistent across varying patient demographics and independent of SCN5A mutation status. Electrophysiological studies demonstrated a significant reduction specifically in sodium current density. Notably, mice injected with BrS plasma showed Brugada-like ECG abnormalities, supporting the pathogenic role of these autoantibodies.

CONCLUSIONS

The study demonstrates the presence of anti-NaV1.5 autoantibodies in the majority of BrS patients, suggesting an immunopathogenic component of the syndrome beyond genetic predispositions. These autoantibodies, which could serve as additional diagnostic markers, also prompt reconsideration of the underlying mechanisms of BrS, as evidenced by their role in inducing the ECG signature of the syndrome in wild-type mice. These findings encourage a more comprehensive diagnostic approach and point to new avenues for therapeutic research.

ST-segment elevation myocardial infarction mimics: The differential diagnosis of nonacute coronary syndrome causes of ST-segment/T-wave abnormalities in the chest pain patient

The evaluation of adult patients suspected of ST-segment elevation myocardial infarction (STEMI) includes a focused history and examination, 12-lead electrocardiogram (ECG), and cardiac serum marker analysis. The ECG plays a pivotal role in the early diagnosis and management of STEMI. A number of ECG entities in this patient population will present with ST-segment elevation and other electrocardiographic abnormalities which can mimic STEMI. In this article, we review the most frequent STEMI mimic patterns, highlight their ECG characteristics, and compare these individual ECG entities to the electrocardiographic abnormalities present with STEMI.

SCN5A gene variants and arrhythmic risk in Brugada syndrome: An updated systematic review and meta-analysis

BACKGROUND

A rare gene variant in SCN5A can be found in approximately 20%-25% of patients with Brugada syndrome (BrS).

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the differences in clinical characteristics of BrS patients with and without SCN5A rare variants and the prognostic role of SCN5A for ventricular arrhythmias in BrS.

METHODS

PubMed and Cochrane Central Register of Controlled Trials (CENTRAL) were systematically searched from inception to January 2024 to identify all relevant studies. Studies were analyzed if they included patients diagnosed with BrS in whom genetic testing for SCN5A variants was performed and arrhythmic outcomes were reported.

RESULTS

A total of 17 studies with 3568 BrS patients, of whom 3030 underwent genetic testing for SCN5A variants, fulfilled the eligibility criteria and were included. Compared with SCN5A- patients, SCN5A+ BrS patients more frequently had spontaneous type 1 electrocardiogram, history of syncope, and documented arrhythmias. Furthermore, higher PQ and QRS intervals in SCN5A+ BrS patients compared with SCN5A- have been found. The pooled analysis demonstrated a significant association between the presence of SCN5A rare variants in BrS patients and the risk of major arrhythmic events, with a pooled odds ratio of 2.14 (95% confidence interval, 1.53-2.99; I2 = 29%).

CONCLUSION

SCN5A+ BrS patients showed a worse clinical phenotype compared with SCN5A-. The pooled analysis demonstrated a significant association between SCN5A+ mutation status and the risk of major arrhythmic events in BrS patients.

Sudden Cardiac Death and Channelopathies: What Lies behind the Clinical Significance of Rare Splice-Site Alterations in the Genes Involved?

Background and objectives: Sudden cardiac death (SCD) is a natural and unexpected death of cardiac origin that occurs within 1 h from the onset of acute symptoms. The major leading causes of SCD are cardiomyopathies and channelopathies. In this review, we focus on channelopathies, inherited diseases caused by mutations affecting genes encoding membrane ion channels (sodium, potassium or calcium channels) or cellular structures that affect Ca2+ availability. The diagnosis of diseases such as long QT, Brugada syndrome, short QT and catecholaminergic polymorphic ventricular tachycardia (CPVT) is still challenging. Currently, genetic testing and next-generation sequencing allow us to identify many rare alterations. However, some non-coding variants, e.g., splice-site variants, are usually difficult to interpret and to classify. Methods: In our review, we searched for splice-site variants of genes involved in channelopathies, focusing on variants of unknown significance (VUSs) registered on ClinVar up to now. Results: The research led to a high number of splice-site VUSs of genes involved in channelopathies, suggesting the performance of deeper studies. Conclusions: In order to interpret the correlation between variants and pathologies, we discuss experimental studies, such as RNA sequencing and functional analysis of proteins. Unfortunately, as these in vitro analyses cannot always be performed, we draw attention to in silico studies as future perspectives in genetics. This review has the aim of discussing the potential methods of detection and interpretation of VUSs, bringing out the need for a future reclassification of variants with currently unknown significance.

Brugada syndrome precipitated by uncomplicated malaria treated with dihydroartemisinin piperaquine: a case report

BACKGROUND

Cardiovascular events following anti-malarial treatment are reported infrequently; only a few studies have reported adverse outcomes. This case presentation emphasizes cardiological assessment of Brugada syndrome, presenting as life-threatening arrhythmia during anti-malarial treatment. Without screening and untreated, this disease may lead to sudden cardiac death.

CASE PRESENTATION

This is a case of 23-year-old male who initially presented with palpitations followed by syncope and shortness of breath with a history of malaria. He had switched treatment from quinine to dihydroartemisinin-piperaquine (DHP). Further investigations revealed the ST elevation electrocardiogram pattern typical of Brugada syndrome, confirmed with flecainide challenge test. Subsequently, anti-malarial treatment was stopped and an Implantable Cardioverter Defibrillator (ICD) was inserted.

CONCLUSIONS

Another possible cause of arrhythmic events happened following anti-malarial consumption. This case highlights the possibility of proarrhytmogenic mechanism of malaria infection and anti-malarial drug resulting in typical manifestations of Brugada syndrome.

Continuous Rhythm Monitoring With Implanted Loop Recorders in Children and Adolescents With Brugada Syndrome

BACKGROUND

Young (<18 years of age) patients with Brugada syndrome (BrS) are often under-represented in BrS studies and their management, especially related to syncopal episodes, remains unclear.

OBJECTIVES

This study sought to describe the arrhythmia prevalence among young patients with BrS undergoing continuous rhythm monitoring by implantable loop recorder (ILR) and to assess the etiology behind syncope of undetermined origin.

METHODS

A total of 147 patients with BrS with ILR were enrolled in 12 international centers and divided into pediatric (age <12 years; n = 77, 52%) and adolescents (age 13-18 years; n = 70, 48%).

RESULTS

Mean age was 11.3 years, 53 patients (36.1%) were female, and 31 (21.1%) had spontaneous type 1 electrocardiograms. Over a median follow-up of 3.6 years (Q1-Q3: 1.6-4.8 years), an arrhythmic event was recorded in 33 patients (22.4%), mainly of nonventricular origin: 15 atrial (10.2%) and 16 bradyarrhythmic events (10.9%). Ventricular arrhythmias occurred in 4 patients, all with spontaneous BrS, and were fever-related in one-half. Among all patients with recurrence of syncope during follow-up, true arrhythmic syncope was documented in 5 (17.8%), and it was due to bradyarrhythmias or atrial arrhythmias in 3 cases (60%).

CONCLUSIONS

Continuous rhythm monitoring with ILRs in young patients with BrS detects a broad range of arrhythmias. Ventricular arrhythmias occur predominantly in patients with spontaneous type 1 electrocardiograms and during fever. Despite the young age, bradyarrhythmias and atrial arrhythmias are frequent and represent the cause of arrhythmic syncope in 60% of patients. Young patients with BrS with syncope of undetermined origin may benefit from ILR implant.

Zebrafish as a Model System for Brugada Syndrome

Brugada syndrome (BrS) is an inheritable cardiac arrhythmogenic disease, associated with an increased risk of sudden cardiac death. It is most common in males around the age of 40 and the prevalence is higher in Asia than in Europe and the United States. The pathophysiology underlying BrS is not completely understood, but several hypotheses have been proposed. So far, the best effective treatment is the implantation of an implantable cardioverter-defibrillator (ICD), but device-related complications are not uncommon. Therefore, there is an urgent need to improve diagnosis and risk stratification and to find new treatment options. To this end, research should further elucidate the genetic basis and pathophysiological mechanisms of BrS. Several experimental models are being used to gain insight into these aspects. The zebrafish (Danio rerio) is a widely used animal model for the study of cardiac arrhythmias, as its cardiac electrophysiology shows interesting similarities to humans. However, zebrafish have only been used in a limited number of studies on BrS, and the potential role of zebrafish in studying the mechanisms of BrS has not been reviewed. Therefore, the present review aims to evaluate zebrafish as an animal model for BrS. We conclude that zebrafish can be considered as a valuable experimental model for BrS research, not only for gene editing technologies, but also for screening potential BrS drugs.

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.

[Cardiac channelopathies in the context of hereditary arrhythmia syndromes]

Genetic arrhythmia disorders are rare diseases; however, they are a common cause of sudden cardiac death in children, adolescents, and young adults. In principle, a distinction can be made between channelopathies and cardiomyopathies in the context of genetic diseases. This paper focuses on the channelopathies long and short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Early diagnosis of these diseases is essential, as drug therapy, behavioral measures, and if necessary, implantation of a cardioverter defibrillator can significantly improve the prognosis and quality of life of patients. This paper highlights the pathophysiological and genetic basis of these channelopathies, describes their clinical manifestations, and comments on the principles of diagnosis, risk stratification and therapy.

Association between the number of altered late potential criteria and increased arrhythmic risk in Brugada syndrome patients

BACKGROUND

Brugada syndrome (BrS) is associated with abnormal electrophysiological properties at right ventricular epicardium, consisting of fragmented electrograms extending well beyond QRS termination. We aimed to evaluate the utility of signal-averaged electrocardiogram (SA-ECG) for the noninvasive assessment of late potentials (LP) and risk stratification of BrS patients.

METHODS

A prospective, observational, single-center study of BrS patients is submitted to SA-ECG with the determination of the total filtered QRS duration (fQRS), root mean square voltage of the 40 ms terminal portion of the QRS (RMS40), and duration of the low-amplitude electric potential component of the terminal portion of the QRS (LAS40). LP were considered positive when above standard cut-offs: fQRS > 114 ms, RMS40 < 20 µV, and LAS40 > 38 ms. The rates of malignant arrhythmic events (MAEs), defined as sudden death or appropriate shocks, were compared in relation to clinical characteristics and SA-ECG findings.

RESULTS

A total of 106 BrS patients (mean age, 48 ± 12 years, 67.9% male) were studied, 49% with type-1 spontaneous pattern and 81% asymptomatic. During a median follow up of 4.7 years, 10 patients (7.1%) suffered MAEs, including 4 sudden deaths. The presence of LP was significantly associated with the arrhythmic risk, which increased with the number of altered LP criteria. In comparison to the patients who had none or 1 altered LP criterium, MAE risk was 4.7 times higher in those with 2 altered criteria and 9.4 times higher in those with 3 altered LP criteria.

CONCLUSIONS

SA-ECG may be a useful tool for risk stratification in BrS. The presence of 2 or 3 abnormal LP criteria could identify a subset of asymptomatic patients at high risk of arrhythmic events.

Clinical differences between drug-induced type 1 Brugada pattern and syndrome

Background

Diagnosis of Brugada syndrome (BrS) may be established by exposing a Type 1 Brugada pattern using a sodium channel blocker. Data on the outcomes of different patient populations with drug-induced Type 1 Brugada pattern are limited. The present study reports on the characteristics and outcome of subjects with ajmaline induced Type 1 Brugada pattern.

Methods

A multicenter retrospective study including all consecutive cases of ajmaline-induced Type 1 Brugada pattern from seven centers.

Results

A total of 260 patients (69.9% males, mean age 43.4 ± 13.5) were included. Additional characteristics included history of syncope (n = 56, 21.5%), family history of BrS (n = 58, 22.3%) or sudden cardiac death (n = 47, 18.1%) and ventricular fibrillation (n = 3, 1.2%). Patients were divided into those meeting current diagnostic criteria for drug-induced BrS (DIBrS) and compared to the drug-induced Brugada pattern (DIBrECG). Females were significantly overrepresented in the DIBrS group (n = 50, 40% vs. n = 29, 21.5%, p = .001). A significantly higher prevalence of type 2/3 Brugada ECG at baseline was found in the DIBrECG group (n = 108, 80.8% vs. n = 75, 60% in the DIBrS, p = .026). During a median follow up of three (IQR 1.50-5.32) years, a single event of significant arrhythmia occurred in the DIBrS group.

Conclusion

Less than half of subjects with ajmaline-induced Brugada pattern met current criteria for BrS. These individuals had very low rate of adverse outcomes during a follow up of 3 years, irrespective of the indication for the test or eligibility for the BrS diagnosis.

A narrative review of inherited arrhythmogenic syndromes in young population: role of genetic diagnosis in exercise recommendations

Sudden cardiac death is a rare but socially devastating event, especially if occurs in young people. Usually, this unexpected lethal event occurs during or just after exercise. One of the leading causes of sudden cardiac death is inherited arrhythmogenic syndromes, a group of genetic entities characterised by incomplete penetrance and variable expressivity. Exercise can be the trigger for malignant arrhythmias and even syncope in population with a genetic predisposition, being sudden cardiac death as the first symptom. Due to genetic origin, family members must be clinically assessed and genetically analysed after diagnosis or suspected diagnosis of a cardiac channelopathy. Early identification and adoption of personalised preventive measures is crucial to reduce risk of arrhythmias and avoid new lethal episodes. Despite exercise being recommended by the global population due to its beneficial effects on health, particular recommendations for these patients should be adopted considering the sport practised, level of demand, age, gender, arrhythmogenic syndrome diagnosed but also genetic diagnosis. Our review focuses on the role of genetic background in sudden cardiac death during exercise in child and young population.

Can Hyperthermia Unveil Brugada Pattern?

Brugada syndrome (BrS) is characterized by ST segment elevations in the right precordial leads, V1 - V3, with additional findings of ventricular arrhythmias and family history (FH) of sudden cardiac death (SCD) at a young age. Here, we describe a case of hyperthermia, unveiling the Brugada electrocardiography (EKG) pattern and the resolution of EKG findings with appropriate hyperthermia management. It is important to distinguish the Brugada EKG pattern from other causes of ST elevations and treat appropriately to prevent patients from developing ventricular fibrillation and SCD. It is key to identify environmental triggers in patients presenting with Brugada EKG pattern and closely monitor for ventricular fibrillation. Educating patients on prompt fever treatment with antipyretics and avoiding medications like sodium channel blockers during the febrile event is paramount to counter patients going into ventricular fibrillation. It is also crucial for close follow-up of these patients, offering them genetic testing for BrS and screening families of patients with BrS.

Demonstration of Arrhythmia Substrate-Associated Dispersion of Repolarization by Epicardial Unipolar Mapping in Brugada Syndrome

BACKGROUND

Epicardial unipolar mapping has not been thoroughly investigated in Brugada syndrome (BrS).

OBJECTIVES

This study aims to examine the characteristics of epicardial unipolar potentials in BrS and investigate the differences from overt cardiomyopathy.

METHODS

Epicardial mapping was performed in 8 patients with BrS and 6 patients with cardiomyopathy. We investigated the J-wave amplitudes using unipolar recordings at delayed potential (DP) sites via bipolar recordings. The repolarization time (RT) at and around the DP recording sites was measured, and maximum dispersion of the RT divided by the distance was defined as the RT dispersion index.

RESULTS

Epicardial mapping at baseline revealed significantly higher J-wave amplitude with bipolar DP in patients with BrS than in patients with cardiomyopathy. J-wave amplitude ≥0.42 mV had 99.1% sensitivity and 100% specificity for diagnosing BrS. The RT dispersion index was significantly higher in patients with BrS than in patients with cardiomyopathy at baseline. In all patients with BrS, coved-type unipolar electrograms without negative T waves (short RT) appeared close to coved-type electrograms with negative T waves (long RT) at the DP recording sites after pilsicainide administration. Thus, a steep RT dispersion was observed in this region, and ventricular arrhythmias emerged from this shorter RT area in all 3 patients with BrS in whom ventricular arrhythmias were induced.

CONCLUSIONS

Bipolar DP-related prominent unipolar J waves and steep repolarization gradients may be more specific for characterizing BrS than for overt cardiomyopathy. Ventricular arrhythmias in BrS are associated with a steep repolarization gradient, indicating phase 2 re-entry as a possible cause.

Association of Late Potentials With Fatal Arrhythmic Events in Patients With Brugada Syndrome-A Meta-analysis

Risk stratification of patients with Brugada syndrome (BrS) remains challenging. Signal-averaged electrocardiogram (SAECG) is a noninvasive tool that can be used to identify the electrophysiologic substrate potentially underlying fatal ventricular arrhythmias. The aim of this meta-analysis is to summarize the existing evidence about the role of late potentials (LP) as a predictor for arrhythmic events in patients with BrS. A systematic search in the MedLine database through to June 2022 without any limitations was performed. Ten studies were included in the quantitative synthesis (1431 patients with BrS, mean age 47.4 years, males 86%). Of these, 1220 patients underwent SAECG evaluation (53.2% had positive LP, and 20.6% had a fatal arrhythmic event). There was a nonsignificant association between positive LPs and fatal arrhythmic events [RR: 2.06 (0.98-4.36), P = 0.06, I 2 = 82%]. By including only studies with patients without a history of fatal arrhythmia, the association between LP with arrhythmic events remained nonsignificant [RR: 1.29 (0.67-2.48), P = 0.44, I 2 = 54%]. In conclusion, there is a possible association between LP and fatal arrhythmic events in patients with BrS, but the literature remains inconclusive. Large cohort studies using a multiparametric approach for risk stratification purposes are needed to improve the risk stratification of BrS and to optimize the selection of BrS patients that should be referred for implantable cardioverter-defibrillator.

Programmed Ventricular Stimulation: Risk Stratification and Guiding Antiarrhythmic Therapies

Electrophysiologic testing with programmed ventricular stimulation (PVS) has been utilized to induce ventricular tachycardia (VT), thereby improving risk stratification for patients with ischemic and nonischemic cardiomyopathies and determining the effectiveness of antiarrhythmic therapies, especially catheter ablation. A variety of procedural aspects can be modified during PVS in order to alter the sensitivity and specificity of the test including the addition of multiple baseline pacing cycle lengths, extrastimuli, and pacing locations. The definition of a positive result is also critically important, which has varied from exclusively sustained monomorphic VT (>30 seconds) to any ventricular arrhythmia regardless of morphology. In this review, we discuss the history of PVS and evaluate its role in sudden cardiac death risk stratification in a variety of patient populations. We propose an approach to future investigations that will capitalize on the unique ability to vary the sensitivity and specificity of this test. We then discuss the application of PVS during and following catheter ablation. The strategies that have been utilized to improve the efficacy of intraprocedural PVS are highlighted during a discussion of the limitations of this probabilistic strategy. The role of noninvasive programmed stimulation is also reviewed in predicting recurrent VT and informing management decisions including repeat ablations, modifications in antiarrhythmic drugs, and implantable cardioverter-defibrillator programming. Based on the available evidence and guidelines, we propose an approach to future investigations that will allow clinicians to optimize the use of PVS for risk stratification and assessment of therapeutic efficacy.

Investigation of a Large Kindred Reveals Cardiac Calsequestrin (CASQ2) as a Cause of Brugada Syndrome

BACKGROUND

Brugada syndrome (BrS) is an inherited primary channelopathy syndrome associated with the risk of ventricular fibrillation (VF) and sudden cardiac death in a structurally normal heart.

AIM OF THE STUDY

The aim of this study was to clinically and genetically evaluate a large family with severe autosomal dominant Brugada syndrome.

METHODS

Clinical and genetic studies were performed. Genetic analysis was conducted with NGS technologies (WES) using the Illumina instrument. According to the standard procedure, variants found by WES were confirmed in all available families by Sanger sequencing. The effect of the variants was studied by using in silico prediction of pathogenicity.

RESULTS

The proband was a 52-year-old man who was admitted to the emergency department for syncope at rest. WES of the index case identified a heterozygous VUS CASQ2, c.532T>C, p.(Tyr178His). We studied the segregation of the variation in all pedigree members. All the patients were heterozygous for the variation CASQ2 p.(Tyr178His), whereas the remaining healthy individuals in the family were homozygous for the normal allele. Structural analysis of CASQ2 p.(Tyr178His) was performed and revealed an important effect of the missense variation on monomer stability. The CASQ2 Tyr180 residue is located inside the sarcoplasmic reticulum (SR) junctional face membrane interaction domain and is predicted to disrupt filamentation.

CONCLUSIONS

Our data suggest that the p.Tyr178His substitution is associated with BrS in the family investigated, affecting the stability of the protein, disrupting filamentation at the interdimer interface, and affecting the subsequent formation of tetramers and polymers that contain calcium-binding sites.

The development of inherited cardiac conditions services: current position and future perspectives

BACKGROUND

Over the last two decades, inherited cardiac conditions (ICC) centres have emerged with the aim of improving outcomes for patients and their families, through early diagnosis, genetic testing, risk assessment and specialist treatment.

SOURCES OF DATA

A literature search was performed using PubMed (https://pubmed.ncbi.nlm.nih.gov/). Commissioned ICC service reviews from NHS England, NHS Improvement and PHG Foundation were evaluated.

AREAS OF AGREEMENT

ICC patient management requires a multi-disciplinary approach. ICC services are predominantly based within tertiary centres. Despite expansion, provision of care remains inadequate to meet rising demands. Access to services is inconsistent, partly due to geographic variation and lack of standardized pathways.

AREAS OF CONTROVERSY

The optimal ICC care model remains undecided, although there is growing interest in 'hub-and-spoke' networks, which could aid secondary and tertiary service integration and repatriation of care.

GROWING POINTS

Genetic mainstreaming is a priority for the Genomic Medicine Service Alliance. The benefits of telehealth and virtual clinics have been validated by their use during the COVID-19 pandemic. Other innovations to improve resource efficiency, such as clinical scientist-led and nurse-led clinics, show promise.

AREAS TIMELY FOR DEVELOPING RESEARCH

An update for the NHS ICC service specifications is planned that appears well timed given the rapid evolution of the ICC landscape in the decade since last review. This has the potential to address needs including national audit, standardized pathways and ICC networks to improve governance and equity of care. Delegation of commissioning for specialist services to integrated care systems may also provide opportunity for increased regional direction.