Early repolarization as a predictor of arrhythmic and nonarrhythmic cardiac events in middle-aged subjects

Vagal response is involved in the occurrence of ventricular fibrillation in patients with early repolarization syndrome

BACKGROUND

Patients with early repolarization syndrome (ERS) and Brugada syndrome (BruS) have comparable clinical symptoms. In both conditions, ventricular fibrillation (VF) is experienced often near midnight or in the early morning hours when the parasympathetic tone is augmented. However, differences between ERS and BruS regarding the risk of VF occurrence have recently been reported. The role of vagal activity remains especially unclear.

OBJECTIVE

The goal of this study was to determine the relationship between VF occurrence and autonomic nervous activity in patients with ERS and BruS.

METHODS

We enrolled 50 patients with ERS (n = 16) and BruS (n = 34) who received an implantable cardioverter-defibrillator. Of these, 20 patients (5 ERS and 15 BruS) experienced VF recurrence (recurrent VF group). We investigated baroreflex sensitivity (BaReS) with the phenylephrine method and heart rate variability using Holter electrocardiography in all patients to estimate autonomic nervous function.

RESULTS

In both patients with ERS and BruS, there was no significant difference in heart rate variability between the recurrent VF and nonrecurrent VF groups. However, in patients with ERS, BaReS was significantly higher in the recurrent VF group than in the nonrecurrent VF group (P = .03); this difference was not evident in patients with BruS. High BaReS was independently associated with VF recurrence in patients with ERS according to Cox proportional hazards regression analyses (hazard ratio 1.52; 95% confidence interval 1.031-3.061; P = .032).

CONCLUSION

Our findings suggest that in patients with ERS, an exaggerated vagal response, as represented by increased BaReS indices, may be involved in the risk of VF occurrence.

Atrial Fibrillation-triggered Ventricular Fibrillation in a Patient with Early Repolarization Syndrome

A 54-year-old man with early repolarization syndrome (ERS) implanted with an implantable cardioverter-defibrillator (ICD) developed persistent atrial fibrillation (AF) three years after the implantation. Similarly, the remote monitoring system begun frequently detecting ventricular fibrillation (VF) and polymorphic ventricular tachycardia (PVT). Longer RR intervals were repeatedly observed just before the initiation of PVT/VF. Catheter ablation for AF successfully diminished both the PVT and VF events.

J wave syndromes: What's new?

Among the inherited ion channelopathies associated with potentially life-threatening ventricular arrhythmia syndromes in nominally structurally normal hearts are the J wave syndromes, which include the Brugada (BrS) and early repolarization (ERS) syndromes. These ion channelopathies are responsible for sudden cardiac death (SCD), most often in young adults in the third and fourth decade of life. Our principal goal in this review is to briefly outline the clinical characteristics, as well as the molecular, ionic, cellular, and genetic mechanisms underlying these primary electrical diseases that have challenged the cardiology community over the past two decades. In addition, we discuss our recently developed whole-heart experimental model of BrS, providing compelling evidence in support of the repolarization hypothesis for the BrS phenotype as well as novel findings demonstrating that voltage-gated sodium and transient outward current channels can modulate each other's function via trafficking and gating mechanisms with implications for improved understanding of the genetics of both cardiac and neuronal syndromes.

Early repolarization pattern in adult females with eating disorders

INTRODUCTION

The risk of cardiovascular death is increased in patients with eating disorders (ED), but the background for this is unknown. Early repolarization pattern (ERP) on the electrocardiogram (ECG) has been associated with increased risk of sudden cardiac death.

METHODS

We investigated the prevalence of ERP in 233 female patients with anorexia nervosa (AN) and bulimia nervosa (BN) (age 18-35 years) compared with 123 healthy female controls.

RESULTS

Early repolarization pattern was present in 52 (22%) of ED patients (16 (15%) AN patients and 36 (29%) BN patients) and 17 (14%) of healthy controls. When adjusting for age, BMI, heart rate, use of selective serotonin reuptake inhibitors (SSRI), and potassium level, the odds ratio (OR) for ERP was 2.1 (95% CI 1.1-4.2, p = .03). There was an increased prevalence of inferolateral ERP in patients with ED compared with healthy controls (OR = 4.3, 95% CI 1.7-11.3, p = .003) as well as ERP with a downward/horizontal sloping ST segment (OR = 3.1, 95% CI 1.3-7.6, p = .01). Additionally, J-point elevation >0.2 mV was more prevalent in patients with ED (OR = 3.3, 95% CI 1.1-9.7, p = .03).

CONCLUSION

The prevalence of ERP was increased in patients with ED compared with healthy controls. This finding may provide a possible explanation for the increased cardiovascular mortality in ED patients.

Electrocardiographic Risk Markers of Cardiac Death: Gender Differences in the General Population

Background

Cardiac death is one of the leading causes of death and sudden cardiac death (SCD) is estimated to cause approximately 50% of cardiac deaths. Men have a higher cardiac mortality than women. Consequently, the mechanisms and risk markers of cardiac mortality are not as well defined in women as they are in men.

Aim

The aim of the study was to assess the prognostic value and possible gender differences of SCD risk markers of standard 12-lead electrocardiogram in three large general population samples.

Methods

The standard 12-lead electrocardiographic (ECG) markers were analyzed from three different Finnish general population samples including total of 20,310 subjects (49.9% women, mean age 44.8 ± 8.7 years). The primary endpoint was cardiac death, and SCD and all-cause mortality were secondary endpoints. The interaction effect between women and men was assessed for each ECG variable.

Results

During the follow-up (7.7 ± 1.2 years), a total of 883 deaths occurred (24.5% women, p < 0.001). There were 296 cardiac deaths (13.9% women, p < 0.001) and 149 SCDs (14.8% women, p < 0.001). Among those who had died due to cardiac cause, women had more often a normal electrocardiogram compared to men (39.0 vs. 27.5%, p = 0.132). After adjustments with common cardiovascular risk factors and the population sample, the following ECG variables predicted the primary endpoint in men: left ventricular hypertrophy (LVH) with strain pattern (p < 0.001), QRS duration > 110 ms (p < 0.001), inferior or lateral T-wave inversion (p < 0.001) and inferolateral early repolarization (p = 0.033). In women none of the variables remained significant predictors of cardiac death in multivariable analysis, but LVH, QTc ≥ 490 ms and T-wave inversions predicted SCD (p < 0.047 and 0.033, respectively). In the interaction analysis, LVH (HR: 2.4; 95% CI: 1.2–4.9; p = 0.014) was stronger predictor of primary endpoint in women than in men.

Conclusion

Several standard ECG variables provide independent information on the risk of cardiac mortality in men but not in women. LVH and T-wave inversions predict SCD also in women.

Relationship between resting 12-lead electrocardiogram and all-cause death in patients without structural heart disease: Shinken Database analysis

Background

Resting 12-lead electrocardiography is widely used for the detection of cardiac diseases. Electrocardiogram readings have been reported to be affected by aging and, therefore, can predict patient mortality.

Methods

A total of 12,837 patients without structural heart disease who underwent electrocardiography at baseline were identified in the Shinken Database among those registered between 2010 and 2017 (n = 19,170). Using 438 electrocardiography parameters, predictive models for all-cause death and cardiovascular (CV) death were developed by a support vector machine (SVM) algorithm.

Results

During the observation period of 320.4 days, 55 all-cause deaths and 23 CV deaths were observed. In the SVM prediction model, the mean c-statistics of 10 cross-validation models with training and testing datasets were 0.881 ± 0.027 and 0.927 ± 0.101, respectively, for all-cause death and 0.862 ± 0.029 and 0.897 ± 0.069, respectively for CV death. For both all-cause and CV death, high values of permutation importance in the ECG parameters were concentrated in the QRS complex and ST-T segment.

Conclusions

Parameters acquired from 12-lead resting electrocardiography could be applied to predict the all-cause and CV deaths of patients without structural heart disease. The ECG parameters that greatly contributed to the prediction were concentrated in the QRS complex and ST-T segment.

Autonomic Influences Related to Early Repolarization in Patients Without Structural Heart Disease

This cross-sectional study focused on the association between heart rate variability (HRV) and early repolarization pattern (ERP). It included 1236 patients categorized into three groups: ERP type 1: J-point elevation with notched/slurred QRS; ERP type 2: ST elevation without dominant J-wave; and non-ERP group. Analyzing time-domain indexes include standard deviation of NN (normal-to-normal) RR intervals (SDNN), root mean square of successive difference in NN RR intervals (RMSSD), and proportion of consecutive NN intervals that differ by more than 50 ms (PNN50), there were significant differences between any two groups (all P < 0.01). All time-domain indexes showed: ERP type 2 > ERP type 1 > non-ERP. Multivariate logistic regression analysis revealed that SDNN at nighttime and gender were independently associated with the maximum magnitude of J-point elevation ≧ 0.2 mV. The findings strongly suggested that based on electrocardiogram characteristics, parasympathetic tone denoted by HRV may be related to different types of ERP.

Out-of-hospital cardiac arrest: Causes according to autopsy and electrocardiography - Analysis of 781 patients with neither hospital care nor prescribed medication during the preceding two years

BACKGROUND

There is a knowledge gap regarding aetiology of and potential for predicting out-of-hospital cardiac arrest (OHCA) among individuals who are healthy before the event.

AIM

To describe causes of OHCA and the potential for predicting OHCA in apparently healthy patients.

METHODS

Patients were recruited from the Swedish Register of Cardiopulmonary Resuscitation from November 2007 to January 2011. Inclusion criteria were: OHCA with attempted CPR but neither dispensed prescription medication nor hospital care two years before the event The register includes the majority of patients suffering OHCA in Sweden where cardiopulmonary resuscitation (CPR) was attempted. Medication status was defined by linkage to the Swedish Prescribed Drug Register. Cause of death was assessed based on autopsy and the Swedish Cause of Death Register. Prediction of OHCA was attempted based on available electrocardiograms (ECG) before the OHCA event.

RESULTS

Altogether 781 individuals (16% women) fulfilled the inclusion criteria. Survival to 30 days was 16%. Autopsy rate was 72%. Based on autopsy, 70% had a cardiovascular aetiology and 59% a cardiac aetiology. An ECG recording before the event was found in 23% of cases. The ECG was abnormal in 22% of them.

CONCLUSION

Among OHCA victims who appeared to be healthy prior to the event, the cause was cardiovascular in the great majority according to autopsy findings. A minority had a preceding abnormal ECG that could have been helpful in avoiding the event.

Electrocardiogram in Haïssaguerre Syndrome (Early Repolarization)

Introduction: Early repolarization pattern (ERP) has traditionally been related as a benign variant of electrocardiography (ECG). However, since 2008, when two studies were published for Haïssaguerre et al. and Rosso et al., with evidence of a higher prevalence of ERP in people with primary or idiopathic ventricular fibrillation (VF), this paradigm has been challenged. Objective: To conduct a thorough review of early repolarization and current state of the art regarding risk stratification in these patients. Methods: Literature review on the subject evaluating the works published in high impact journals. Conclusion: The correlation of risk factors and the real value of the various methods currently available as possible risk stratifiers is still controversial. Advances in genetics and molecular biology may in the future help in understanding the pathophysiology and better risk stratification in this population. In this context, the standardization of the definition and classification of early repolarization is imperative, as it will serve as a substrate for future studies and researches in the area.

Eletrocardiograma na Síndrome de Haïssaguerre (Repolarização Precoce)

Introdução: O padrão de repolarização precoce (RP) tem sido tradicionalmente relacionado como uma variante benigna do eletrocardiograma (ECG). No entanto, desde 2008, quando dois estudos foram publicados por Haïssaguerre et al. e Rosso et al., com evidências de maior prevalência de RP em pessoas acometidas por fibrilação ventricular (FV) primária ou idiopática, esse paradigma tem sido contestado. Objetivo: Realizar uma profunda revisão acerca da RP e atual estado da arte acerca da estratificação de risco nesses pacientes. Métodos: Revisão da literatura acerca do tema avaliando os trabalhos publicados em revistas de alto impacto e a experiência dos especialistas sobre o assunto. Conclusão: A correlação de fatores de risco e o real valor dos vários métodos atualmente disponíveis como possíveis estratificadores de risco ainda são controversos. Avanços nas áreas da genética e biologia molecular podem futuramente auxiliar no entendimento da fisiopatologia e melhor estratificação de risco nessa população. Neste contexto, a padronização da definição e classificação da repolarização precoce mostra-se imperativa, uma vez que servirá de substrato para futuros estudos e pesquisas na área.

A novel mutation in GPD1‑L associated with early repolarization syndrome via modulation of cardiomyocyte fast sodium currents

Early repolarization syndrome (ERS) is associated with genetic mutations, but the role of the glycerol‑3‑phosphate dehydrogenase 1‑like (GPD1‑L) mutation remains unclear. The aim of the present study was to investigate the role and potential underlying mechanism of GPD1‑L mutation P112L in the pathogenesis of ERS. Whole‑genome sequencing was performed on samples from a family with ERS, and the gene sequencing results were analyzed using bioinformatics. 293 cells were transfected with wild‑type (WT) or mutant‑type (MT) GPD1‑L and SCN5A plasmids. Successful transfection of GPD1‑L in 293 cells was verified by western blotting. Whole‑cell patch‑clamp recording, confocal microscopic observation and western blotting were used to uncover the potential mechanism of GPD1‑L P112L in ERS. The results of western blotting indicated that the expression of the GPD1‑L protein was lower in the MT group compared with that in the WT group, but the mock group did not express the GPD1‑L protein. The whole‑cell patch‑clamp recording results indicated that the activation current density of INa (at ‑30 mV) was ~60% lower in the MT group compared with the WT group (P<0.01). The mutation caused the inactivation voltage to move in a negative direction by ~3 mV compared with that of the WT group. However, there were no significant between‑group differences in the steady activation, steady inactivation, and steady recovery of INa. Confocal microscopy demonstrated that MT GPD1‑L was less expressed near the cell membrane and more expressed in the cytoplasm compared with WT GPD1‑L. Both WT and MT GPD1‑L were highly expressed in the cytoplasm and in small amounts in the nucleus. In conclusion, the GPD1‑L P112L mutation decreased INa activation and GPD1‑L cell expression, including in the region near the cell membrane. These results suggest that GPD1‑L P112L may be a pathogenic genetic mutation associated with ERS.

Early repolarization in the inferior leads after accessory pathway ablation is highly correlated with atrial fibrillation in Wolff-Parkinson-White syndrome

BACKGROUND

Both atrial fibrillation (AF) and early repolarization (ER) are highly prevalent in patients with Wolff-Parkinson-White (WPW) syndrome.

METHODS

We retrospectively identified 123 WPW patients with manifest accessory pathway (mAP) and 105 patients with concealed accessory pathways (cAP) who underwent successful ablation of the APs. AF history prior to the ablation was investigated. The presence of ER was evaluated from the 12-lead electrocardiograms performed both before and immediately after the ablation. Patients were further followed up for AF occurrence after the AP ablation.

RESULTS

Compared with cAP patients, WPW patients presented with higher incidence of previous AF, as well as ER after the AP ablation. Compared with those without AF history, WPW patients with comorbid AF were more prone to presenting ER, especially in the inferior leads, after the mAP ablation. Regression analysis suggested that the post-ablation ER in the inferior leads was strongly associated with AF in WPW patients [OR = 5.85; 95% confidence interval (CI): 2.29-14.96], even after adjusting for age and left atrial diameter (OR = 5.14; 95% CI: 1.80-14.74). Moreover, post-ablation inferior-lead ER was predictive of AF recurrence after mAP ablation during the follow-up of 22.6 ± 11.1 months. In comparison, ER was correlated with neither AF history nor AF recurrence in patients undergoing cAP ablation.

CONCLUSIONS

ER in the inferior leads after the mAP ablation is highly correlated with AF history and recurrence in WPW patients.

Prolongation of The Activation Time in Ischemic Myocardium is Associated with J-wave Generation in ECG and Ventricular Fibrillation

J-wave pattern has been recognized as an arrhythmic risk marker, particularly in myocardial infarction patients. Mechanisms underlying J-wave development in ischemia remain unknown. In myocardial infarction model, we evaluated activation time delay as a prerequisite of J-wave appearance and predictor of ventricular fibrillation. Body surface ECGs and myocardial unipolar electrograms were recorded in 14 anesthetized pigs. 48 intramural leads were positioned across ventricular free walls and interventricular septum. Myocardial ischemia was induced by ligation of the left anterior descending coronary artery and the recordings were done during 40-minute coronary occlusion. The local activation times were determined as instants of dV/dt minimum during QRS complex in unipolar electrograms. During occlusion, ventricular local activation time prolonged in the middle portion of the left ventricular free wall, and basal and middle portions of septum, while J-waves appeared in precordial leads in 11 animals. In logistic regression and ROC curve analyses, activation time delay at a given time-point was associated with J-wave development, and a longer activation time was associated with ventricular fibrillation appearance. In experimental coronary occlusion, activation delay in ischemic myocardium was associated with generation of the J waves in the body surface ECG and predicted ventricular fibrillation.

Depolarization versus repolarization abnormality underlying inferolateral J-wave syndromes: New concepts in sudden cardiac death with apparently normal hearts

Early repolarization indicates a distinct electrocardiographic phenotype affecting the junction between the QRS complex and the ST segment in inferolateral leads (inferolateral J-wave syndromes). It has been considered a benign electrocardiographic variant for decades, but recent clinical studies have demonstrated its arrhythmogenicity in a small subset, supported by experimental studies showing transmural dispersion of repolarization. Here we review the current knowledge and the issues of risk stratification that limit clinical management. In addition, we report on new mapping data of patients refractory to pharmacologic treatment using high-density electrogram mapping at the time of inscription of J wave. These data demonstrate that distinct substrates, delayed depolarization, and abnormal early repolarization underlie inferolateral J-wave syndromes, with significant implications. Finally, based on these data, we propose a new simplified mechanistic classification of sudden cardiac deaths without apparent structural heart disease.

The Atrial Phenotype of the Inherited Primary Arrhythmia Syndromes

Over the past two decades, our understanding of inherited primary arrhythmia syndromes has been enriched by studies that have aimed to define the clinical characteristics and the genetic, cellular and molecular features predisposing patients to an enhanced risk of ventricular arrhythmias. In contrast, very little is known about the causative role of inherited cardiac channelopathies on atrial conduction abnormalities possibly leading to different atrial tachyarrhythmias. The diagnostic and therapeutic management of patients with an inherited cardiac channelopathy presenting with atrial arrhythmias remains highly challenging and is in urgent need of improvement. This review will assess the current knowledge on atrial electrical abnormalities affecting patients with different forms of inherited primary arrhythmia syndromes, including long and short QT syndromes, early repolarisation syndrome, catecholaminergic polymorphic ventricular tachycardia and Brugada syndrome.

Early repolarization and risk of lone atrial fibrillation

INTRODUCTION

Early repolarization syndrome is a recently proposed condition characterized by an early repolarization pattern in the electrocardiogram (ECG) and ventricular fibrillation in the absence of structural heart abnormalities. Although some studies have suggested that early repolarization is associated with frequency of atrial fibrillation, the association of early repolarization with atrial fibrillation is not well known.

HYPOTHESIS

Early repolarization indicates the substrate for atrial fibrillation in addition to that for ventricular fibrillation.

METHOD

This study included 79 patients (57 men [72%]; age, 45 ± 12 years) aged less than 60 years who had paroxysmal lone atrial fibrillation and 395 age- and sex-matched healthy controls (patient:control ratio, 1:5). Patients who had structural heart disease, hypertension, diabetes, hyperthyroidism, history of successful resuscitation, or the Brugada type ECG were excluded. ECGs recorded during sinus rhythm were compared between patients with atrial fibrillation and healthy controls.

RESULTS

Early repolarization in the inferior and/or lateral leads was more common in patients with atrial fibrillation (25%) than controls (10%; P = 0.001). The location and magnitude of early repolarization were similar between the two groups. Other electrocardiographic measurements were not different between the two groups. Among patients with atrial fibrillation, there was no difference in clinical characteristics including age at atrial fibrillation development, sex, and body mass index between patients with early repolarization and those without early repolarization. Electrocardiographic measurements were not different between patients with early repolarization and those without early repolarization.

CONCLUSION

Early repolarization was associated with lone atrial fibrillation. Early repolarization may indicate increased susceptibility to atrial fibrillation.

Waveform prototype-based feature learning for automatic detection of the early repolarization pattern in ECG signals

OBJECTIVE

Our aim was to develop an automated detection method, for prescreening purposes, of early repolarization (ER) pattern with slur/notch configuration in electrocardiogram (ECG) signals using a waveform prototype-based feature vector for supervised classification.

APPROACH

The feature vectors consist of fragments of the ECG signal where the ER pattern is located, instead of abstract descriptive variables of ECG waveforms. The tested classifiers included linear discriminant analysis, k-nearest neighbor algorithm, and support vector machine (SVM).

MAIN RESULTS

SVM showed the best performance in Friedman tests in our test data including 5676 subjects representing 45 408 leads. Accuracies of the different classifiers showed results well over 90%, indicating that the waveform prototype-based feature vector is an effective representation of the differences between ECG signals with and without the ER pattern. The accuracy of inferior ER was 92.74% and 92.21% for lateral ER. The sensitivity achieved was 91.80% and specificity was 92.73%.

SIGNIFICANCE

The algorithm presented here showed good performance results, indicating that it could be used as a prescreening tool of ER, and it provides an additional identification of critical cases based on the distances to the classifier decision boundary, which are close to the 0.1 mV threshold and are difficult to label.

[Not Available]

This review includes main positions of the revision of diagnostic criteria of "J-wave syndromes in the J-Wave Syndromes Expert Consensus Conference Report: Emerging Concepts and Gaps in Knowledge" (2016). The article, systematized according to the sections of the above-mentioned document, outlines the questions of terminology, new criteria for diagnosis of the Brugada syndrome (BrS) and early repolarization syndrome (ERS). The section devoted to ERS on the issues of new terminology and standardization of measurements, is supplemented with material from the Consensus Paper - The Early Repolarization Pattern (2015). The article also presents the issues of differential diagnosis in BrS, presents modulating factors, defines acquired Brugada-pattern and Brugada phenocopies. The similarities and differences between BrS and ERS are presented in a comparative aspect.

The early repolarization pattern: Echocardiographic characteristics in elite athletes

BACKGROUND

The electrocardiographic early repolarization (ER) pattern is associated with idiopathic ventricular fibrillation and increased long-term cardiovascular mortality. Whether structural cardiac aberrations influence the phenotype is unclear. Since ER is particularly common in athletes, we evaluated its prevalence and investigated predisposing echocardiographic characteristics and cardiopulmonary exercise capacity in a cohort of elite athletes.

METHODS

A total of 623 elite athletes (age 21 ± 5 years) were examined during annual preparticipation screening from 2006 until 2012 including electrocardiography, echocardiography, and exercise testing. ECGs were analyzed with focus on ER. All athletes participated in a clinical follow-up.

RESULTS

The prevalence of ER was 17% (108/623). ER-positive athletes were predominantly male (71%, 77/108), showed a lower heart rate (57.1 ± 9.3 bpm versus 60.0 ± 11.2 bpm; p = 0.015) and a higher lean body mass compared to ER-negative participants (88.1% ± 5.6% versus 86.5% ± 6.3%; p = 0.015). Echocardiographic measurements and cardiopulmonary exercise capacity in male and female athletes with and without ER largely showed similar results. Only the notching ER subtype (n = 15) was associated with an increased left atrial diameter (OR 7.01, 95%CI 1.65-29.83; p = 0.008), a higher left ventricular mass (OR 1.02, 95%CI 1.00-1.03; p = 0.038) and larger relative heart volume (OR 1.01, 95%CI 1.00-1.01; p = 0.01). During a follow-up of 7.4 ± 1.5 years, no severe cardiovascular event occurred in the study sample.

CONCLUSIONS

In elite athletes presence of ER is not associated with distinct alterations in echocardiography and cardiopulmonary exercise. Athletes presenting with ER are rather male, lean with a low heart rate.

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.

Prevalence of early repolarization syndrome and long-term clinical outcome in patients with the diagnosis of idiopathic ventricular fibrillation

Idiopathic ventricular fibrillation (IVF) is diagnosed in up to 14% of sudden cardiac death (SCD) survivors. Early repolarization syndrome (ERS) in patients with ventricular tachyarrhythmia is characterized by an elevated J-point in inferior and/or antero-lateral leads. Our objectives were to determine the prevalence of ERS in IVF patients, and to evaluate potential differences in clinical outcome. Out of 3,552 implantable cardioverter defibrillator (ICD) carriers, 758 SCD survivors were retrospectively identified from the databases of the Medical Universities of Vienna and Innsbruck within the last three decades. Early repolarization pattern (ERP) was classified either as "notching" or "slurring". Endpoints were defined as appropriate ICD therapies for ventricular tachyarrhythmia, either anti-tachycardia pacing or shock, and all-cause mortality. After exclusion of recognized reasons for SCD, 50 patients were assigned to the diagnosis of IVF (6.6%). An ERP was identified in 10 patients, most of them with notching (n = 8). After a mean follow-up of 11.2 ± 6.7 years (539.3 patient years), appropriate ICD therapies were found in 50% of ERS and 43% of IVF patients without ERP (p = 0.732). In ERS patients, all ICD therapies were found in patients with notching pattern. Similarly, incidence of inappropriate ICD therapies, and all-cause mortality was comparable (30% vs. 23%, p = 0.707; 10% vs. 5%, p = 0.496, respectively). In 758 SCD survivors, we found a low prevalence of IVF and ERS. Similar event rates were reported concerning all-cause mortality and ICD therapies for ventricular tachyarrhythmia after long-term follow-up in this cohort.

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.

Ventricular and Supraventricular Ectopy in Subjects With Early Repolarization

Early repolarization (ER) is a common electrocardiographic (ECG) finding that is associated with an increased risk of idiopathic ventricular fibrillation and sudden cardiac death. This study investigated whether the presence of ER is a predictor of ventricular and supraventricular ectopy as a marker for electrical instability. Standard 12-lead electrocardiograms of the first follow-up in the population-based Study of Health in Pomerania (SHIP-1) (n = 3,300, age 20 to 79 years) were analyzed to identify subjects with an ER pattern. Ventricular and supraventricular ectopy was assessed via portable tele-ECG cards recording 2 electrocardiograms daily over the course of 4 weeks. Data of 1,630 subjects (n = 83,833 ECG card recordings, average 51.4 per subject) were analyzed for ventricular and supraventricular ectopy using a standardized automated algorithm. Associations of ER and several forms of arrhythmias were assessed using a 2-sided Fisher's exact test or t test, where appropriate. Overall, prevalence of ER in the SHIP-1 population was 4.8%. Presence of ER was not associated with the occurrence of ventricular and supraventricular arrhythmias (p ≥0.05 for all analyses). Furthermore, subgroup analyzes for ER localization (inferior) and ST-segment morphology (horizontal/descending) did not show any association with arrhythmic events. In conclusion, presence of the ER pattern is not associated with an increased occurrence of ventricular or supraventricular arrhythmias as assessed by serial ECG card recordings in this large population-based sample.

The Role of the Ratio of J-Point Elevation Magnitude and R-Wave Amplitude on the Same ECG Lead in the Risk Stratification of Subjects With Early Repolarization Pattern

BACKGROUND

Just as high-risk populations for cardiac arrest exist in patients with Brugada syndrome or long QT syndrome, high-risk and low-risk populations for cardiac arrest also exist in patients with early repolarization pattern (ERP).

HYPOTHESIS

Electrocardiographic (ECG) characteristics can aid the risk stratification of patients with ERP.

METHODS

Electrocardiographic parameters such as magnitude of J-point elevation and J/R ratio were measured. The magnitude of J-point elevation, leads with J points elevated, J/R ratio, morphology of the ST segment, and QT/QTc interval were used in comparative analysis in 2 groups: 57 patients with ERP and cardiac arrest (cardiac arrest group) and 100 patients with ERP but without cardiac arrest (control group).

RESULTS

There was no statistical difference in clinical characteristics of the 2 groups. The J/R ratio in the cardiac arrest group was significantly higher than in the control group (26.8% ± 18.1% vs 16.3% ± 10.3%, respectively; P < 0.001) and the proportion of horizontal/descending ST segments (70.2%) was significantly higher than in the control group (29.0%), but the proportion of ascending/upsloping ST segments (29.8%) was significantly lower than in the control group (71.0%; P < 0.001). Multivariate logistic regression revealed that higher J/R ratio and horizontal/descending ST segment were independently associated with increased risk of cardiac arrest in patients with ERP.

CONCLUSIONS

In patients with ERP and cardiac arrest, J/R ratios were relatively higher and mostly with horizontal/descending ST segments, suggesting that J/R ratio and ST-segment morphology may be used as indicators for risk stratification in patients with ERP.

Atrial arrhythmias in inherited arrhythmogenic disorders

Atrial arrhythmias are being increasingly recognized in inherited arrhythmogenic disorders particularly in patients with Brugada syndrome and short QT syndrome. Atrial arrhythmias in inherited arrhythmogenic disorders have significant epidemiologic, clinical, and prognostic implications. There has been progress in the understanding of underlying genetic characteristics and the mechanistic link between atrial arrhythmias and inherited arrhythmogenic disorders. Appropriate management of these patients is of paramount importance.

Early Repolarisation - What Should the Clinician Do?

The early repolarisation (ER) pattern is a common ECG finding. Most individuals with the ER pattern are at minimal risk for arrhythmic events. In others, ER increases the arrhythmic risk of underlying cardiac pathology. Rarely ER syndrome will manifest as a primary arrhythmogenic disorder causing ventricular fibrillation (VF). ER syndrome is defined as syncope attributed to ventricular arrhythmias or cardiac arrest attributed to ER following systematic exclusion of other etiologies. Some ECG features associated with ER portend a higher risk. However, clinically useful risk-stratifying tools to identify the asymptomatic patient at high risk are lacking. Patients with asymptomatic ER and no family history of malignant ER should be reassured. All patients with ER should continue to have modifiable cardiac risk factors addressed. Symptomatic patients should be systematically investigated, directed by symptoms.

Sudden Cardiac Death Risk Stratification - An Update

Sudden cardiac death (SCD) remains a major public health problem worldwide, yet current methods to identify those at greatest risk are inadequate. High-risk individuals may benefit from potentially life-saving treatment, such as insertion of an implantable-cardioverter defibrillator (ICD). However, such treatments are expensive and have their own associated risks. Furthermore, most cases of SCD occur in the general adult population who may be relatively asymptomatic but yet have an underlying predisposition to SCD. Hence, there is great interest and clinical need in improving methods for risk stratification of SCD to identify those at greatest risk and implement the most appropriate treatment. This review provides an update on current risk-stratification methods for SCD in high-risk groups, in particular patients with reduced left ventricular function following acute myocardial infarction and those with non-ischaemic dilated cardiomyopathy, and highlights some novel methods that may have a role to play in future risk-stratification schemes. Approaches and challenges for SCD risk stratification among the general public are also discussed.

Genetics of inherited primary arrhythmia disorders

A sudden unexplained death is felt to be due to a primary arrhythmic disorder when no structural heart disease is found on autopsy, and there is no preceding documentation of heart disease. In these cases, death is presumed to be secondary to a lethal and potentially heritable abnormality of cardiac ion channel function. These channelopathies include congenital long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, and short QT syndrome. In certain cases, genetic testing may have an important role in supporting a diagnosis of a primary arrhythmia disorder, and can also provide prognostic information, but by far the greatest strength of genetic testing lies in the screening of family members, who may be at risk. The purpose of this review is to describe the basic genetic and molecular pathophysiology of the primary inherited arrhythmia disorders, and to outline a rational approach to genetic testing, management, and family screening.