Electrocardiographic and Electrophysiologic Characteristics in Patients With Brugada Type Electrocardiogram and Inducible Ventricular Fibrillation Single Center Experience

Does the Age of Sudden Cardiac Death in Family Members Matter in Brugada Syndrome?

Background Brugada syndrome is an inherited cardiac channelopathy associated with major arrhythmic events (MAEs). The presence of a positive family history of sudden cardiac death (SCD) as a risk predictor of MAE remains controversial. We aimed to examine the association between family history of SCD and MAEs stratified by age of SCD with a systematic review and meta-analysis. Methods and Results We searched the databases of MEDLINE and EMBASE from January 1992 to January 2020. Data from each study were combined using the random-effects model. Fitted metaregression was performed to evaluate the association between the age of SCD in families and the risk of MAE. Twenty-two studies from 2004 to 2019 were included in this meta-analysis involving 3386 patients with Brugada syndrome. The overall family history of SCD was not associated with increased risk of MAE in Brugada syndrome (pooled odds ratio [OR], 1.11; 95% CI, 0.82-1.51; P=0.489, I²=45.0%). However, a history of SCD in family members of age younger than 40 years of age did increase the risk of MAE by ≈2-fold (pooled OR, 2.03; 95% CI, 1.11-3.73; P=0.022, I²=0.0%). When stratified by the age of cut point at 50, 45, 40, and 35 years old, a history of SCD in younger family member was significantly associated with a higher risk of MAE (pooled OR, 0.49, 1.30, 1.51, and 2.97, respectively; P=0.046). Conclusions A history of SCD among family members of age younger than 40 years was associated with a higher risk of MAE.

Gender Differences in Prognosis and Risk Stratification of Brugada Syndrome: A Pooled Analysis of 4,140 Patients From 24 Clinical Trials

Background: Male gender has been consistently shown to be a risk factor for a greater number of arrhythmic events in patients with Brugada Syndrome (BrS). However, there have been no large-scale comprehensive pooled analyses to statistically and systematically verify this association. Therefore, we conducted a pooled analysis on gender differences in prognosis and risk stratification of BrS with a largest sample capacity at present.

Methods: We searched PubMed, Embase, Medline, Cochrane Library databases, Chinese National Knowledge Infrastructure, and Wanfang Data for relevant studies published from 2002 to 2017. The prognosis and risk stratification of BrS and risk factors were then investigated and evaluated according to gender.

Results: Twenty-four eligible studies involving 4,140 patients were included in the analysis. Male patients (78.1%) had a higher risk of arrhythmic events than female patients (95% confidence interval: 1.46–2.91, P < 0.0001). Among the male population, there were statistical differences between symptomatic patients and asymptomatic patients (95% CI: 2.63–7.86, P < 0.00001), but in the female population, no statistical differences were found. In the female subgroup, electrophysiological study (EPS) positive patients had a tendency toward a higher risk of arrhythmic events than EPS-negative patients (95% CI: 0.93–29.77, P = 0.06).

Conclusions: Male patients are at a higher risk of arrhythmic events than female patients. Within the male population, symptomatic patients have a significantly higher risk profile compared to asymptomatic patients, but no such differences are evident within the female population. Consequently, in the female population, the risk of asymptomatic patterns cannot be underestimated.

Programmed Ventricular Stimulation for Risk Stratification in the Brugada Syndrome: A Pooled Analysis

BACKGROUND

The role of programmed ventricular stimulation in identifying patients with Brugada syndrome at the highest risk for sudden death is uncertain.

METHODS AND RESULTS

We performed a systematic review and pooled analysis of prospective, observational studies of patients with Brugada syndrome without a history of sudden cardiac arrest who underwent programmed ventricular stimulation. We estimated incidence rates and relative hazards of cardiac arrest or implantable cardioverter-defibrillator shock. We analyzed individual-level data from 8 studies comprising 1312 patients who experienced 65 cardiac events (median follow-up, 38.3 months). A total of 527 patients were induced into arrhythmias with up to triple extrastimuli. Induction was associated with cardiac events during follow-up (hazard ratio, 2.66; 95% confidence interval [CI], 1.44-4.92, P<0.001), with the greatest risk observed among those induced with single or double extrastimuli. Annual event rates varied substantially by syncope history, presence of spontaneous type 1 ECG pattern, and arrhythmia induction. The lowest risk occurred in individuals without syncope and with drug-induced type 1 patterns (0.23%, 95% CI, 0.05-0.68 for no induced arrhythmia with up to double extrastimuli; 0.45%, 95% CI, 0.01-2.49 for induced arrhythmia), and the highest risk occurred in individuals with syncope and spontaneous type 1 patterns (2.55%, 95% CI, 1.58-3.89 for no induced arrhythmia; 5.60%, 95% CI, 2.98-9.58 for induced arrhythmia).

CONCLUSIONS

In patients with Brugada syndrome, arrhythmias induced with programmed ventricular stimulation are associated with future ventricular arrhythmia risk. Induction with fewer extrastimuli is associated with higher risk. However, clinical risk factors are important determinants of arrhythmia risk, and lack of induction does not necessarily portend low ventricular arrhythmia risk, particularly in patients with high-risk clinical features.

Meta-Analysis on Risk Stratification of Asymptomatic Individuals With the Brugada Phenotype

The prognosis of asymptomatic subjects remains the most controversial issue in Brugada syndrome (BS). A meta-analysis on the prognostic role of spontaneous type 1 electrocardiographic (ECG) pattern and programmed ventricular stimulation (PVS) in asymptomatic subjects with Brugada electrocardiogram was performed. Current databases were searched until March 2014. Fourteen prospective observational studies were included in the present meta-analysis, accumulating data on 3,536 asymptomatic subjects (2,820 men) with BS phenotype. The mean follow-up period varied from 20 and 77 months. Data regarding 1,398 asymptomatic subjects with spontaneous type 1 ECG pattern of BS were retrieved from 6 studies. During follow-up, arrhythmic events (sustained ventricular tachycardia/fibrillation, appropriate device therapies, or arrhythmic death) occurred in 42 patients (3%). The meta-analysis of these studies demonstrated that asymptomatic subjects with spontaneous type 1 ECG pattern of BS exhibit an increased risk of future arrhythmic events (odds ratio = 3.56, 95% confidence interval 1.70 to 7.47, Z = 3.37, p = 0.0008); 1,104 asymptomatic subjects with BS ECG pattern from 12 studies underwent PVS and were available for analysis. During follow-up, arrhythmic events occurred in 36 subjects (3.3%). Inducible ventricular arrhythmias at PVS were predictive of future arrhythmic events (odds ratio = 3.51, 95% confidence interval 1.60 to 7.67, Z = 3.14, p = 0.002). In conclusion, this meta-analysis showed that asymptomatic subjects with either spontaneous diagnostic ECG pattern or inducible ventricular arrhythmias at PVS are at increased risk.

Genetic, molecular and cellular mechanisms underlying the J wave syndromes

An early repolarization (ER) pattern in the ECG, distinguished by J-point elevation, slurring of the terminal part of the QRS and ST-segment elevation has long been recognized and considered to be a benign electrocardiographic manifestation. Experimental studies conducted over a decade ago suggested that some cases of ER may be associated with malignant arrhythmias. Validation of this hypothesis was provided by recent studies demonstrating that an ER pattern in the inferior or inferolateral leads is associated with increased risk for life-threatening arrhythmias, termed ER syndrome (ERS). Because accentuated J waves characterize both Brugada syndrome (BS) and ERS, these syndromes have been grouped under the term "J wave syndromes". ERS and BS share similar ECG characteristics, clinical outcomes and risk factors, as well as a common arrhythmic platform related to amplification of I(to)-mediated J waves. Although BS and ERS differ with respect to the magnitude and lead location of abnormal J wave manifestation, they can be considered to represent a continuous spectrum of phenotypic expression. Although most subjects exhibiting an ER pattern are at minimal to no risk, mounting evidence suggests that careful attention should be paid to subjects with "high risk" ER. The challenge ahead is to be able to identify those at risk for sudden cardiac death. Here I review the clinical and genetic aspects as well as the cellular and molecular mechanisms underlying the J wave syndromes.

Right ventricular histological substrate and conduction delay in patients with Brugada syndrome

The reported pathogenesis of Brugada syndrome is phase 2 reentry resulting from shortening of the epicardial action potential duration at the right ventricular outflow tract (RVOT). However, several studies have revealed a high incidence of ventricular late potentials and high rate of ventricular fibrillation (VF) induced by programmed ventricular stimulation (PVS). The aim of the present study was to evaluate the role of slow conduction at the RVOT for the initiation of VF by PVS and any underlying pathological conditions in Brugada syndrome. Endocardial mapping of the RVOT and endomyocardial biopsy of the right ventricle were performed in 25 patients with Brugada syndrome with inducible VF. Late potentials were positive in 11 of the 25 (44%) patients. Low-amplitude fragmented and delayed electrograms were recorded at the RVOT in 13 of 18 (72.2%) patients. Histologic examination of the biopsy samples revealed fatty tissue infiltration, interstitial fibrosis, lymphocyte infiltration, and/or myocyte disorganization in 13 patients. Slow conduction at the RVOT may contribute to the induction of VF by PVS in Brugada syndrome. Various pathomorphologic changes may contribute to slow conduction at the RVOT.

Tpeak-Tend interval and Tpeak-Tend/QT ratio as markers of ventricular tachycardia inducibility in subjects with Brugada ECG phenotype

AIMS

The present study investigated whether several ECG markers of ventricular repolarization are associated with ventricular tachycardia/fibrillation (VT/VF) inducibility in subjects with type 1 ECG pattern of Brugada syndrome (BS).

METHODS AND RESULTS

The clinical data of 23 individuals (19 males, age 42.69 +/- 14.63) with spontaneous (n = 10) or drug-induced (n = 13) type 1 ECG pattern of BS who underwent programmed ventricular stimulation were analysed. Sustained VT/VF was induced in 17 subjects (74%) and was significantly associated with the presence of spontaneous type 1 ECG of BS (P = 0.012). Among the studied ECG repolarization markers, subjects with inducible VT/VF displayed an increased T(peak)-T(end) interval in leads V(2) (88.82 +/- 15.70 vs. 78.33 +/- 4.08 ms, P = 0.02) and V(6) (76.33 +/- 10.08 vs. 66.66 +/- 5.16 ms, P = 0.04) and a greater T(peak)-T(end)/QT ratio in lead V(6) (0.214 +/- 0.028 vs. 0.180 +/- 0.014, P = 0.009) compared with those without arrhythmias. Ventricular tachycardia/fibrillation inducibility was not associated with arrhythmic events during a mean follow-up period of 4.61 +/- 2.14 years (P = 0.739).

CONCLUSION

The T(peak)-T(end) interval and T(peak)-T(end)/QT ratio were associated with VT/VF inducibility in BS. The utility of T(peak)-T(end)/QT ratio as a new marker of arrhythmogenesis in BS requires further studies, including a large number of patients.

Dynamic change in ST-segment and spontaneous occurrence of ventricular fibrillation in Brugada syndrome with a novel nonsense mutation in the SCN5A gene during long-term follow-up

A 67-year-old male underwent genetic testing under the diagnosis of Brugada syndrome because of recurrent ventricular fibrillation with coincident ST-segment elevation in either right precordial, inferior leads or both since the age of 55 years. Screening of gene mutations using denaturing high-performance liquid chromatography (DHPLC) and direct sequencing identified a novel nonsense mutation (R179X) of SCN5A in a heterozygous manner. The functional assay for the identified mutation, using a whole-cell patch clamp in the heterologous expression system, revealed that the nonsense mutation, located in the second transmembrane segment of the first domain (DI-S2) of the alpha-subunit, failed to synthesize the complete structure of the cardiac sodium channel, thus causing the non-functional channel. Coding effects by the gene mutation was altered during the 12-year follow-up, which might affect the clinical features of the patient through the ion channel density in the ventricle, dynamics of repolarization abnormality and conduction disturbance.

Brugada syndrome: recent advances and controversies

The Brugada syndrome, first described as a new clinical entity in 1992, is widely recognized today as a form of inherited sudden cardiac arrest. The past 16 years witnessed a progressive increase in the number of reported cases and a dramatic proliferation of articles serving to define the clinical, genetic, cellular, ionic, and molecular aspects of the disease. This article provides a brief overview of recent advances in our understanding of the clinical presentation and molecular and cellular mechanisms and an update of existing controversies.