Clinical characteristics of patients with spontaneous or inducible ventricular fibrillation without apparent heart disease presenting with J wave and ST segment elevation in inferior leads

Evaluation of cases with early repolarization on electrocardiogram and normal population in terms of laboratory and clinical results

Aim: Early repolarization (ER) is a frequent indication, and it is important to correctly evaluate the effects of its benign and malignant forms in terms of prognosis. It was aimed to compare ER cases with the normal population in terms of multi-vessel disease, bypass and mortality. Material and Method: This study comprised 776 patients aged 18 and older who admitted the emergency department between January 2015 and December 2020. 377 of these patients had ER in the electrocardiogram (ECG), 409 patients had normal ECGs and were added to the study as the control group. Age, gender, multi-vessel disease, by-pass and mortality relations of the patients were evaluated with angiographic findings. Results: The mean age of 786 patients was 50.49±6.82 years, 372 (47.3%) were female, and the age range was 23-66 years (p

Delayed depolarization and histologic abnormalities underlie the Brugada syndrome

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

Why Is There an Increased Risk for Sudden Cardiac Death in Patients With Early Repolarization Syndrome?

The last two decades have changed the viewpoint on early repolarization syndrome (ERS). The prevalence of the early repolarization pattern is variable and ranges between 3-24% depending upon age, gender, and criteria used for J-point upliftment from baseline (0.05mV vs. 1 mV). While this pattern was previously linked with a benign result, multiple recent investigations have found a link between early repolarization and Sudden Cardiac Death (SCD) by causing life-threatening arrhythmias like Ventricular tachycardia/Ventricular fibrillation, a condition known as early repolarization syndrome. The syndrome falls under a broader bracket of J wave syndromes, which can be caused by early repolarization or depolarization abnormalities. The characteristics of early repolarization that are considered high risk for Sudden Cardiac Death include the amplitude of J-point upliftment from baseline ( > 0.2 mV), Inferior-lateral location of Early Repolarization pattern, and horizontal and downsloping ST-segment. Patients with symptomatic early repolarisation patterns on ECG are more likely to have repeated cardiac episodes. Implantable Cardioverter-Defibrillator (ICD) implantation and isoproterenol are the recommended treatments in symptomatic patients. On the other hand, asymptomatic patients with early repolarization patterns are prevalent and have a better outcome. Risk categorization is still obscure in asymptomatic early repolarization patterns. This traditional review outlines the known knowledge of pathophysiology behind the increased risk of sudden cardiac death, risk stratification of patients with ERS, and the treatment guidelines for patients with ERS. Further prospective studies are recommended to elucidate the exact mechanism for ventricular arrhythmogenesis in ERS patients and to risk stratifying asymptomatic patients with ERS.

The diagnostic value of 2D-speckle tracking echocardiography for identifying subclinical ventricular dysfunction in subjects with early repolarization pattern

INTRODUCTION

Early repolarization pattern (ERP) can exist a silent substrate for arrhytmic events in accordance with the previous studies which have shown there has been evidence of morphological changes in left ventricle (LV) in ERP subjects. Despite structural changes in ERP subjects, it has not exactly known whether a change in LV functional parameters occur in ERP. The aim of our study was to investigate LV functional parameters in ERP athletes evaluated by 2D- speckle tracking echocardiography (2D-STE).

METHOD

In this study, athletes with ERP (n = 50) and athletes without ERP (n = 50) were recruited between April 2018 and September 2018. For each case, 2D- TTE and 2D- STE evaluation were performed by the same cardiologist.

RESULTS

Left ventricle mean global longitudinal strain (GLS) (P < .001) and GLS at all apical chamber views (P < .001), longitudinal peak systolic strain rate (SRS) at A3C (P: .011), early diastolic strain rate (SRE) at A3C (P < .001) and late diastolic strain rate (SRA) at A3C (P: .034) in the ERP athletes were significantly lower than those in the athletes without ERP. LV basal segment circumferential SRS (P: .002) and SRE (P: .006) were significantly lower in ERP athletes compared to athletes without ERP. LV mechanical dispersion was significantly higher in ERP athletes compared to athletes without ERP (P < .001).

CONCLUSION

Our study suggests ERP can be more associated with impaired LV longitudinal function than circumferential function. In addition, both LV inferolateral region and basal segment can be more affected functionally in ERP athletes.

Ventricular Arrhythmias and Sudden Cardiac Death

Ventricular arrhythmias remain a significant cause of sudden cardiac death (SCD), and knowledge of their cause and high-risk features is important. SCD occurs when the interaction between vulnerable substrates and acute triggers results in sustained ventricular tachycardia progressing to ventricular fibrillation. Here, the authors aim to review the role of ventricular arrhythmias in SCD, first by approaching the substrates that support ventricular arrhythmias, and then by exploring features of these substrates and the acute triggers that may lead to SCD.

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

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

J Wave Syndromes: History and Current Controversies

The concept of J wave syndromes was first proposed in 2004 by Yan et al for a spectrum of electrocardiographic (ECG) manifestations of prominent J waves that are associated with a potential to predispose affected individuals to ventricular fibrillation (VF). Although the concept of J wave syndromes is widely used and accepted, there has been tremendous debate over the definition of J wave, its ionic and cellular basis and arrhythmogenic mechanism. In this review article, we attempted to discuss the history from which the concept of J wave syndromes (JWS) is evolved and current controversies in JWS.

Early repolarization syndrome: A cause of sudden cardiac death

Early repolarization syndrome (ERS), demonstrated as J-point elevation on an electrocardiograph, was formerly thought to be a benign entity, but the recent studies have demonstrated that it can be linked to a considerable risk of life - threatening arrhythmias and sudden cardiac death (SCD). Early repolarization characteristics associated with SCD include high - amplitude J-point elevation, horizontal and/or downslopping ST segments, and inferior and/or lateral leads location. The prevalence of ERS varies between 3% and 24%, depending on age, sex and J-point elevation (0.05 mV vs 0.1 mV) being the main determinants. ERS patients are sporadic and they are at a higher risk of having recurrent cardiac events. Implantable cardioverter-defibrillator implantation and isoproterenol are the suggested therapies in this set of patients. On the other hand, asymptomatic patients with ERS are common and have a better prognosis. The risk stratification in asymptomatic patients with ERS still remains a grey area. This review provides an outline of the up-to-date evidence associated with ERS and the risk of life - threatening arrhythmias. Further prospective studies are required to elucidate the mechanisms of ventricular arrhythmogenesis in patients with ERS.

J wave syndromes: a decade of progress

OBJECTIVE

The objective was to provide a brief history of J wave syndromes and to summarize our current understanding of their molecular, ionic, cellular mechanisms, and clinical features. We will also discuss the existing debates and further direction in basic and clinical research for J wave syndromes.

DATA SOURCES

The publications on key words of "J wave syndromes", "early repolarization syndrome (ERS)", "Brugada syndrome (BrS)" and "ST-segment elevation myocardial infarction (STEMI)" were comprehensively reviewed through search of the PubMed literatures without restriction on the publication date.

STUDY SELECTION

Original articles, reviews and other literatures concerning J wave syndromes, ERS, BrS and STEMI were selected.

RESULTS

J wave syndromes were firstly defined by Yan et al. in a Chinese journal a decade ago, which represent a spectrum of variable phenotypes characterized by appearance of prominent electrocardiographic J wave including ERS, BrS and ventricular fibrillation (VF) associated with hypothermia and acute STEMI. J wave syndromes can be inherited or acquired and are mechanistically linked to amplification of the transient outward current (I to )-mediated J waves that can lead to phase 2 reentry capable of initiating VF.

CONCLUSIONS

J wave syndromes are a group of newly highlighted clinical entities that share similar molecular, ionic and cellular mechanism and marked by amplified J wave on the electrocardiogram and a risk of VF. The clinical challenge ahead is to identify the patients with J wave syndromes who are at risk for sudden cardiac death and determine the alternative therapeutic strategies to reduce mortality.

Some Controversies about Early Repolarization: The Haïssaguerre Syndrome

Controversy has followed the groundbreaking and cornerstone paper of Haïssaguerre et al. Much of this controversy has been due to the use of the term "early repolarization pattern" and possible waveform morphologies on the standard 12-lead ECG ( it is 10 second strip) that could predict who will manifest the malignant arrhythmogenic syndrome described by Haïssaguerre et al. The standard ECG definition of early repolarization pattern (ERP) or early repolarization variant (ERV) since then has changed its clinical meaning for a surface electrocardiographic waveform from benign to malignant. The new definition of ERP/ERV contains only J wave but ST-segment elevation is no more obligatory. In the old definition, early repolarization pattern (ERP) or early repolarization variant (ERV) 3 is a well-recognized idiopathic electrocardiographic phenomenon considered to be present when at least two adjacent precordial leads show elevation of the ST segment, with values equal or higher than 1 mm. In the new electrocardiographic ERP concept, the ST segment may or may not be elevated and can be up-sloping, horizontal or down-sloping while in the old ERP/ERV concept it must be elevated at least 1 mm in at least two adjacent leads and the variant is characterized by a diffuse elevation of the ST segment of upper concavity, ending in a positive T wave of V2 to V4 or V5 and prominent J wave and ST-segment elevation predominantly in left precordial leads. The phenomenon constitutes a normal variant; it is almost a rule in athletes (present in 89% of the cases in this universe).

J Wave Syndrome: Clinical Diagnosis, Risk Stratification and Treatment

J wave syndrome has emerged from a benign electrocardiographic abnormality to a proarrythmic state and a significant cause of idiopathic ventricular fibrillation responsible for sudden cardiac death. Electrical genesis, genetics and ionic mechanisms of J wave syndromes are active areas of research. Typically two of these viz., Early repolarization syndrome (ER) and Brugada syndrome (BrS) are fairly well characterized enabling correct diagnosis in most patients. In early repolarization syndrome, J waves are seen in inferior (2,3, avF) or lateral leads (V4, V5, V6), while in Brugada syndrome they are best seen in right precordial leads (V1-V3). The first part of repolarization of ventricular myocardium is governed by Ito current i.e., rapid outward potassium current. The proposed mechanism of ventricular fibrillation (VF) and ventricular tachycardia (VT) storms is faster Ito current in the epicardium than in the endocardium resulting in electrical gradient that forms the substrate for phase 2 re-entry. Prevention of Ito current with quinidine supports this mechanism. Morphological features of benign variety of J wave syndrome and malignant/ proarrythmic variety have now been fairly well characterized. J waves are very common in young, athletes and blacks; risk stratification for VF/sudden cardiac death (SCD) is not easy. Association of both ER syndrome and Brugada syndrome with other disease states like coronary artery disease is being reported frequently. Those with ECG abnormality as the only manifestation are difficult to manage. Certain ECG patterns are more proarrythmic. Individuals resuscitated from VF definitely need an implantable cardiac defibrillator (ICD) but in others there is no consensus regarding therapy. Role of electrophysiology study to provoke ventricular tachycardia or fibrillation is not yet well defined. Radiofrequency ablation of epicardial substrate in right ventricle in Brugada syndrome is reported and is also under critical evaluation. In this review we shall discuss some interesting historical features, epidemiology, electrocardiographic features, and ionic mechanisms on pathogenesis, clinical features, risk stratification and treatment issues in J wave syndromes. Brugada syndrome is not discussed in this review.

Benign clinical significance of J-wave pattern (early repolarization) in highly trained athletes

BACKGROUND

J wave/QRS slurring (early repolarization) on 12-lead ECG has been associated with increased risk for ventricular fibrillation in the absence of cardiovascular (CV) disease.

OBJECTIVE

The purpose of this study was to assess the prevalence and clinical significance of J wave/QRS slurring in a large population of competitive athletes.

METHODS

Seven hundred four athletes (436 males [62%], age 25 ± 5 years) free of CV disease who had engaged in 30 different sports were examined. Serial clinical, ECG, and echocardiographic evaluations were available over 1 to 18 years of follow-up (mean 6 ± 4 years).

RESULTS

J wave was found in 102 athletes (14%) and was associated with QRS slurring in 32 (4%). It was found most commonly in anterior, lateral, and inferior leads (n = 73 [72%]), occasionally in lateral leads (n = 26 [25%]), and rarely in inferior leads (n = 3 [3%]). Most of 102 athletes (n = 86 [84%]) also showed ST-segment elevation. J wave/QRS slurring was associated with other training-related ECG changes (ie, increased R/S-wave voltages in 76%) and left ventricular (LV) morphologic remodeling (LV mass 199 ± 48 g vs 188 ± 56 g, P <.05). During follow-up, no athlete with J wave experienced cardiac event or ventricular tachyarrhythmias, or developed structural CV disease.

CONCLUSION

In athletes, early repolarization pattern usually is associated with other ECG changes, such as increased QRS voltages and ST-segment elevation, as well as LV remodeling, suggesting that it likely represents another benign expression of the physiologic athlete's heart. J wave (early repolarization) is common in highly trained athletes and does not convey risk for adverse cardiac events, including sudden death or tachyarrhythmias.

Electrocardiographic methods for diagnosis and risk stratification in the Brugada syndrome

The Brugada syndrome (BrS) is a malignant, genetically-determined, arrhythmic syndrome manifesting as syncope or sudden cardiac death (SCD) in individuals with structurally normal hearts. The diagnosis of the BrS is mainly based on the presence of a spontaneous or Na + channel blocker induced characteristic, electrocardiographic (ECG) pattern (type 1 or coved Brugada ECG pattern) typically seen in leads V1 and V2 recorded from the 4th to 2nd intercostal (i.c.) spaces. This pattern needs to be distinguished from similar ECG changes due to other causes (Brugada ECG phenocopies). This review focuses mainly on the ECG-based methods for diagnosis and arrhythmia risk assessment in the BrS. Presently, the main unresolved clinical problem is the identification of those patients at high risk of SCD who need implantable cardioverter-defibrillator (ICD), which is the only therapy with proven efficacy. Current guidelines recommend ICD implantation only in patients with spontaneous type 1 ECG pattern, and either history of aborted cardiac arrest or documented sustained VT (class I), or syncope of arrhythmic origin (class IIa) because they are at high risk of recurrent arrhythmic events (up to 10% or more annually for those with aborted cardiac arrest). The majority of BrS patients are asymptomatic when diagnosed and considered to have low risk (around 0.5% annually) and therefore not indicated for ICD. The majority of SCD victims in the BrS, however, had no symptoms prior to the fatal event and therefore were not protected with an ICD. While some ECG markers such as QRS fragmentation, infero-lateral early repolarisation, and abnormal late potentials on signal-averaged ECG are known to be linked to increased arrhythmic risk, they are not sufficiently sensitive or specific. Potential novel ECG-based strategies for risk stratification are discussed based on computerised methods for depolarisation and repolarisation analysis, a composite approach targeting several major components of ventricular arrhythmogenesis, and the collection of large digital ECG databases in genotyped BrS patients and their relatives.

Early repolarisation and J wave syndromes

J wave syndrome has emerged as a significant cause of Idiopathic ventricular fibrillation (IVF) responsible for sudden cardiac death. A large body of data is now available on genesis, genetics and ionic mechanisms of J wave syndromes. Two of these viz., Early repolarization syndrome (ER) and Brugada syndrome (BrS) are fairly well characterized enabling correct diagnosis in most patients. The first part of repolarization of ventricular myocardium is governed by Ito current i.e., rapid outward potassium current. The proposed mechanism of ventricular fibrillation (VF) and ventricular tachycardia (VT) storms is the faster Ito current in the epicardium than in the endocardium results in electrical gradient that forms the substrate for phase 2 reentry. Prevention of Ito current with quinidine supports this mechanism. Majority of ER patterns in young patients are benign. The key issue is to identify those at increased risk of sudden cardiac death. Association of both ER syndrome and Brugada syndrome with other disease states like coronary artery disease has also been reported. Individuals resuscitated from VF definitely need an implantable cardiac defibrillator (ICD) but in others there is no consensus regarding therapy. Role of electrophysiology study to provoke ventricular tachycardia or fibrillation is not yet well defined. Radiofrequency ablation of epicardial substrate in right ventricle in Brugada syndrome is also under critical evaluation. In this review we shall discuss historical features, epidemiology, electrocardiographic features, ionic pathogenesis, clinical features and current status of proposed treatment of ER and BrS.

Early repolarization increases the occurrence of sustained ventricular tachyarrhythmias and sudden death in the chronic phase of an acute myocardial infarction

BACKGROUND

We recently showed that the presence of early repolarization (ER) increases the risk of ventricular fibrillation occurrences in the early phase of acute myocardial infarction (AMI). This study aimed to clarify whether an association exists between ER and occurrences of ventricular tachyarrhythmias or sudden death in the chronic phase of AMI.

METHODS AND RESULTS

This study retrospectively enrolled 1131 patients (67±12 years; 862 men) with AMIs surviving 14 days post-AMI. The primary end point was the occurrence of sustained ventricular tachyarrhythmias or sudden death >14 days after the AMI onset. We evaluated the presence of ER from the predischarge ECG (mean 10±3 days post-AMI). ER was defined as an elevation of the terminal portion of the QRS complex of >0.1 mV in inferior or lateral leads. After a median follow-up of 26.2 months, 26 patients had an episode of ventricular tachyarrhythmias or sudden death. A multivariable Cox regression analysis revealed the presence of ER (hazard ratio, 5.37; 95% confidence interval, 2.27-12.69; P<0.001), Killip class on admission of >I (hazard ratio, 2.75; 95% confidence interval, 1.24-6.07; P=0.013), and a left ventricular ejection fraction of <35% (hazard ratio, 11.83; 95% confidence interval, 5.16-27.13; P<0.001) were significantly associated with event occurrences. As features of the ER pattern, ER in the inferior leads, high-amplitude ER, a notched morphology, and ER without ST-segment elevation were associated with an increased risk of event occurrences.

CONCLUSIONS

ER observed at a mean of 10 days post-AMI may be a marker for a subsequent risk of ventricular tachyarrhythmias or sudden death.

Early repolarization pattern: its ECG characteristics, arrhythmogeneity and heritability

Early repolarization (ER) has been accepted as a benign ECG variant for decades. Two seminal studies challenged this notion and have demonstrated that ER pattern is associated with an increased risk of arrhythmic and cardiac mortality in patients with idiopathic ventricular fibrillation (IVF) and in the general population. Recent clinical studies demonstrate its varying impact as an arrhythmogenic substrate on different diseases. For example, in ER syndrome, a primary electrical disease, ER appears as a major arrhythmogenic substrate for development of VF whereas in patients with coronary artery disease, an ER pattern may exist as a silent substrate, increasing the risk of VF during episodes of cardiac ischaemia. Due to the high prevalence of an ER pattern in the general population and a low VF event rate, it remains challenging to differentiate a malignant ER pattern from a benign form. Recent research suggests that a J-wave amplitude of more than 0.1 mV combined with a descending/horizontal ST segment may constitute a malignant ER pattern. Further studies are however necessary to evaluate its prognostic value for cardiac and arrhythmic death in the general population as well as in cases with a malignant ER pattern. While genetic testing has revealed putative causal DNA variants in sporadic cases, the lack of co-segregation with the disease in affected families suggests that ER syndrome is not monogenic but is likely a complex disorder influenced by multiple genetic as well as environmental factors.

The Brugada Syndrome - Diagnosis, Clinical Implications and Risk Stratification

The Brugada syndrome (BrS) is a hereditary arrhythmic syndrome manifesting as syncope or sudden cardiac death (SCD) in individuals without overt structural heart disease. Currently, its diagnosis is mainly based on the presence of a spontaneous or Na+-channel blocker induced so-called "type 1" Brugada electrocardiographic (ECG) pattern typically seen in leads V1 and V2 recorded from the 4th to 2nd intercostal spaces. Presently the main unresolved clinical problem in the BrS is the identification of patients at high risk of SCD who need implantable cardioverter-defibrillator (ICD). Current guidelines recommend ICD implantation only in patients with spontaneous type 1 ECG pattern and either history of aborted cardiac arrest or documented sustained ventricular tachycardia (class I) or syncope of arrhythmic origin (class IIa) because they are at high risk of recurrent arrhythmias. However, the majority of BrS patients are asymptomatic when diagnosed and have generally low risk (0.5 % annually or lower) and therefore are not indicated for ICD. Most of SCD victims in the BrS have had no symptoms prior to the fatal event and therefore were not protected with an ICD. Currently there are no reliable methods to identify these potential victims of SCD. Although some ECG markers such as QRS fragmentation and infero-lateral early repolarisation have been demonstrated to signify increased arrhythmic risk their value still needs to be confirmed in large prospective studies. Novel risk assessment strategies need to be developed based on computerised quantitative ECG analysis of large digital ECG databases in patients with BrS and their relatives, and combined assessment of the most important factors of ventricular arrhythmogenesis.

Prognostic significance of early repolarization in inferolateral leads in Brugada patients with documented ventricular fibrillation: a novel risk factor for Brugada syndrome with ventricular fibrillation

BACKGROUND

Little is known about the clinical and prognostic impact of early repolarization (ER) on patients with Brugada syndrome (BrS), especially those with documented ventricular fibrillation (VF).

OBJECTIVE

To investigate the prevalence and prognostic significance of ER in inferolateral leads in patients with BrS and documented VF.

METHODS

We investigated 10 different 12-lead electrocardiograms (ECGs) recorded on different days to identify the presence of ER, which was defined as J-point elevation ≥0.1 mV in inferior (II, III, aVF) or lateral leads (I, aVL, V₄-V₆), in 49 individuals (46 men; age 46 ± 13 years) with a type 1 ECG of BrS and previous history of VF.

RESULTS

ER was observed persistently (in all ECGs) in 15 patients (31%; P group), intermittently (in at least one but not in all ECGs) in 16 patients (33%; I group), and not observed in 18 patients (37%; N group), yielding an overall ER incidence of 63% (31/49). During the follow-up period (7.7 years), recurrence of VF was documented in all 15 patients (100%) in the P group, and less in 12 patients (75%) in the I group and in 8 patients (44%) in the N group. The P group showed a worse prognosis than N group (P = .0001) by Kaplan-Meier analysis. Either persistent or intermittent ER in an inferolateral lead was an independent predictor of fatal arrhythmic events (hazard ratio 4.88, 95% confidence interval 2.02-12.7, P = .0004; and hazard ratio 2.50, 95% confidence interval 1.03-6.43, P = .043, respectively).

CONCLUSION

The prevalence of ER in inferolateral leads was high and an especially persistent form of ER was associated with a worse outcome in BrS patients with documented VF.

Idiopathic ventricular fibrillation, early repolarization and other J wave-related ventricular fibrillation syndromes: from an electrocardiographic enigma to an electrophysiologic dogma

Current clinical and experimental data demonstrate that the electrocardiographic J wave plays a critical role in the pathogenesis of ventricular fibrillation (VF) in patients with Brugada syndrome (BS) and early repolarization (ER) syndrome (ERS). This has generated renewed interest in the presence of J waves and ERS in the general population, yet the identification of high-risk ECG markers and the risk stratification of subjects with ERS remain to be established. More recently, this concept has been expanded to VF mechanisms in patients with structural heart diseases. Some of the fatal arrhythmias in the setting of acute myocardial ischemia or infarction may share a similar, J wave-related electrophysiologic process. In canine arterially perfused wedge preparations, the occurrence of J wave-related arrhythmias is mediated by phase 2 reentry. The stability of the action potential (AP) dome in the ventricular epicardium is dependent on the prominence of the AP phase 1 notch. The ability to maintain the AP dome depends on a delicate balance between inward and outward ionic currents during depolarization and the early phase of repolarization. Outward shifts of the balance and inability to maintain the AP dome result in marked dispersion of repolarization and vulnerability to VF. This review describes the electrocardiographic and clinical features of the J waves in idiopathic VF and other structural heart diseases.

The J wave and fragmented QRS complexes in inferior leads associated with sudden cardiac death in patients with chronic heart failure

AIMS

To investigate the relationship between electrocardiogram (ECG) parameters [J wave, fragmented QRS (fQRS), QTc, the peak-to-end interval of T wave (Tp-Te)], and sudden cardiac death (SCD) in chronic heart failure (CHF).

METHODS AND RESULTS

The ECGs of 1570 CHF patients, 572 cases with dilated cardiomyopathy (DCM) and 998 cases with ischaemic cardiomyopathy (ICM) were analysed with the endpoint being an SCD or non-SCD (NSCD). During a median follow-up period of 36 months (0.40-65 months), 438 (27.89%) patients died, of which 158 (35.84%) were SCD. Overall, the occurrence of J wave, fQRS, and long Tp-Te were greater in SCD patients than that of NSCD patients (all P< 0.01). For DCM cases, more SCD patients had J waves observed in the inferior leads than that in the NSCD group (26.78 vs. 13.07%, P<0.001). However, ICM cases with SCD did have more fQRS in the inferior leads than that with NSCD (42.16 vs. 26.67%, P= 0.01). After adjusting for other risk factors, Cox regression analysis revealed that presence of J wave or fQRS in the inferior leads predicted a higher risk for SCD in DCM [hazard ratio (HR), 4.095; 95% confidence interval (CI), 2.132-7.863] and ICM (HR, 2.714; 95% CI, 1.809-4.072) patients. A left ventricular ejection fraction ≤ 30% also predicted SCD and NSCD in DCM and ICM patients. In contrast, the predictive value of QTc and Tp-Te for SCD was not significant.

CONCLUSIONS

Presence of J wave or fQRS in the inferior leads predicted higher risk of SCD in DCM and ICM patients and might serve as independent predictors for SCD in patients with CHF.

Early repolarization is an independent predictor of occurrences of ventricular fibrillation in the very early phase of acute myocardial infarction

BACKGROUND

Recent evidence has linked early repolarization (ER) to idiopathic ventricular fibrillation (VF) in patients without structural heart disease. However, no studies have clarified whether or not there is an association between ER and the VF occurrences after the onset of an acute myocardial infarction (AMI).

METHODS AND RESULTS

This study retrospectively included 220 consecutive patients with an AMI (57 female; mean age, 69±11 years) in whom the 12-lead ECGs before the AMI onset could be evaluated. The patients were classified on the basis of a VF occurrence within 48 hours after the AMI onset. Early repolarization was defined as an elevation of the QRS-ST junction of >0.1 mV from baseline in at least 2 inferior or lateral leads, manifested as QRS slurring or notching. Twenty-one (10%) patients had a VF occurrence within 48 hours of the AMI onset. A multivariate analysis revealed that ER (odds ratio [OR], 7.31; 95% confidence interval [CI], 2.21-24.14; P<0.01), a time from the onset to admission of <180 minutes (OR, 3.77; 95% CI, 1.13-12.59; P<0.05), and a Killip class greater than I (OR, 13.60; 95% CI, 3.43-53.99; P<0.001) were independent predictors of VF occurrences. As features of the ER pattern, a J-point elevation in the inferior leads, greater magnitude of the J-point elevation, notched morphology of the ER, and ER with a horizontal/descending ST segment, all were significantly associated with a VF occurrence.

CONCLUSIONS

The presence of ER increased the risk of VF occurrences within 48 hours after the AMI onset.

Circadian and seasonal variations of ventricular tachyarrhythmias in patients with early repolarization syndrome and Brugada syndrome: analysis of patients with implantable cardioverter defibrillator

INTRODUCTION

The circadian and seasonal patterns of ventricular tachyarrhythmia (VTA) in patients with early repolarization syndrome (ERS) have not been determined. We compared the timing of VTAs in patients with ERS and Brugada syndrome (BS).

METHODS AND RESULTS

We enrolled patients with ERS (n = 14) and BS (n = 53) who underwent implantable cardioverter defibrillator (ICD) implantation. The timing of VTAs, including cardiac arrest and appropriate shocks, was determined. During follow up of 6.4 ± 3.6 years in the ERS group and 5.0 ± 3.3 years in the BS group, 5 of 14 (36%) ERS and 10 of 53 (19%) BS patients experienced appropriate shocks (P = 0.37). Cardiac arrest showed a trend of nocturnal distribution peaking from midnight to early morning (P = 0.14 in ERS, P = 0.16 in BS). Circadian distribution of appropriate shocks showed a significant nocturnal peak in patients with ERS (P < 0.0001) but a trend toward a nocturnal peak in patients with BS (P = 0.08). There were no seasonal differences in cardiac arrest in patients with ERS and BS. However, patients with ERS showed a seasonal peak in appropriate shocks from spring to summer (P < 0.0001). There was no significant seasonal peak in patients with BS. The timing of VTAs (cardiac arrest plus appropriate shock) showed significant nocturnal distributions in patients with ERS and BS (P < 0.01, respectively). A significant clustering of VTAs was noted from spring to summer (P < 0.01) in patients with ERS, but not in patients with BS (P = 0.42).

CONCLUSIONS

Incidence of VTAs showed marked circadian variations with night-time peaks in patients with ERS and BS.

Novel indexes of heterogeneity of ventricular repolarization in subjects with early repolarization pattern

AIM

The presence of early repolarization (ER) in inferior or inferolateral leads has been associated with malignant arrhythmias and increased mortality. Transmural dispersion of repolarization (TDR) has been proposed to underlie arrhythmogenesis in J-wave syndromes. The present study investigated specific electrocardiographic (ECG) markers including Tpeak-Tend interval and (Tpeak-Tend)/QT ratio that reflect TDR in subjects with ER.

METHODS AND RESULTS

The ECGs of 47 healthy individuals (43 males, mean age: 45.7 ± 13.1 years) with an ER pattern in lateral (n = 15) or infero-lateral leads (n = 32) who successfully completed an exercise stress test were analysed at rest, peak workload, and recovery. The ER pattern was defined as slurring or notching of the terminal part of the QRS complex (J-point) ≥ 1 mm, in at least two contiguous leads. Thirty-five age- and sex-matched healthy subjects without ER (28 males, mean age: 48.6 ± 10.2 years) served as comparative controls. Subjects with ER displayed increased Tpeak-Tend interval in lead V(2), Tpeak-Tend dispersion of the precordial leads, and (Tpeak-Tend)/QT ratio in lead V(2) compared with those without ER in all three phases of the exercise test (P < 0.05). In addition, Tpeak-Tend dispersion and the (Tpeak-Tend)/QT ratio in lead V(2) were significantly increased at recovery phase compared with peak exercise only in subjects with ER (P< 0.05). There were no significant differences among the studied ECG parameters regarding the ER location (lateral vs. infero-lateral), the ER type (slurring or notching), or the maximum J-point amplitude (≥ 1.5 vs. <1.5 mm) at baseline ECGs.

CONCLUSIONS

Individuals with ER display an increased TDR that may be related to an increased arrhythmic risk.

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

BACKGROUND

Recently, we and others reported that early repolarization (J wave) is associated with idiopathic ventricular fibrillation. However, its clinical and genetic characteristics are unclear.

METHODS AND RESULTS

This study included 50 patients (44 men; age, 45 ± 17 years) with idiopathic ventricular fibrillation associated with early repolarization, and 250 age- and sex-matched healthy controls. All of the patients had experienced arrhythmia events, and 8 (16%) had a family history of sudden death. Ventricular fibrillation was inducible by programmed electric stimulation in 15 of 29 patients (52%). The heart rate was slower and the PR interval and QRS duration were longer in patients with idiopathic ventricular fibrillation than in controls. We identified nonsynonymous variants in SCN5A (resulting in A226D, L846R, and R367H) in 3 unrelated patients. These variants occur at residues that are highly conserved across mammals. His-ventricular interval was prolonged in all of the patients carrying an SCN5A mutation. Sodium channel blocker challenge resulted in an augmentation of early repolarization or development of ventricular fibrillation in all of 3 patients, but none was diagnosed with Brugada syndrome. In heterologous expression studies, all of the mutant channels failed to generate any currents. Immunostaining revealed a trafficking defect in A226D channels and normal trafficking in R367H and L846R channels.

CONCLUSIONS

We found reductions in heart rate and cardiac conduction and loss-of-function mutations in SCN5A in patients with idiopathic ventricular fibrillation associated with early repolarization. These findings support the hypothesis that decreased sodium current enhances ventricular fibrillation susceptibility.

Clinical and electrocardiographic characteristics of patients with short QT interval in a large hospital-based population

BACKGROUND

Short QT syndrome is one of the underlying disorders associated with ventricular fibrillation. However, the precise prognostic implication of a short QT interval remains unclear.

OBJECTIVE

The purpose of this study was to investigate the prevalence and long-term prognosis in patients with a shorter-than-normal QT interval in a large hospital-based population.

METHODS

We chose patients with a short Bazett QTc interval from a database consisting of 114,334 patients to determine the clinical characteristics and prognostic value of a short QT interval.

RESULTS

A total of 427 patients (mean age 43.4 ± 22.4 years) had a short QT interval with about a 1.2 times higher male predominance (234 men). The QTc interval was significantly longer in female than in male patients (363.8 ± 6.1 ms vs 357.1 ± 5.8 ms, P <.0001). The age-specific prevalence of patients with short QT interval was biphasic, peaking at young and old age. Atrial fibrillation and early repolarization were complicated with short QT interval in 39 (9.1%) and 26 (6.1%) patients, respectively. The prognosis of 327 patients (182 men; mean age, 46.4 ± 27.3 years) with a short QT interval could be assessed (mean follow-up period, 54.0 ± 62.0 months). During the follow-up, 2 patients, 1 of whom had early repolarization, developed life-threatening events, in contrast to 6 patients who died of noncardiac causes and did not have early repolarization.

CONCLUSION

The prevalence of a short QT interval showed a slight male preponderance and biphasic age-dependent distribution in both genders. The complication rate of atrial fibrillation was higher in those with a short QT interval than in general populations. The long-term outcome suggested that early repolarization in a short QT interval might be associated with potential risk of lethal arrhythmia.

Effect of sodium-channel blockade on early repolarization in inferior/lateral leads in patients with idiopathic ventricular fibrillation and Brugada syndrome

BACKGROUND

A high incidence of early repolarization (ER) pattern in the inferolateral leads has been reported in patients with idiopathic ventricular fibrillation (IVF). Brugada syndrome (BS) is characterized by J-point or ST-segment elevation in the right precordial leads and ventricular fibrillation, and some patients with BS also have ER in the inferolateral leads.

OBJECTIVE

To compare the clinical characteristics and effects of sodium-channel blockade on ER between IVF patients with ER (early repolarization syndrome [ERS]) and BS patients with or without ER.

METHODS

Fourteen patients with ERS and 21 patients with BS were included in this study. ER was defined as an elevation of at least 0.1 mV from baseline in the QRS-T junction in the inferorolateral leads. Provocative tests with sodium-channel blockers were conducted in all patients with ERS to distinguish ERS from BS.

RESULTS

In the ERS group, all patients were male and most patients experienced ventricular fibrillation during sleep or low activity (79%). ER was attenuated by sodium-channel blockers in most patients with ERS (13/14, 93%) and BS (5/5, 100%), whereas ST-segment elevation was augmented in the right precordial leads in the BS group. The rates of positive late potentials were significantly higher in the BS group (60%) than in the ERS group (7%) (P <.01).

CONCLUSIONS

Some similarities were observed between ERS and BS, including gender, arrhythmia triggers, and response of ER to sodium-channel blockers. Unlike the ST segment in the right precordial leads in BS, ER was attenuated in patients with both ERS and BS, suggesting a differential mechanism between ER in the inferolateral leads and ST elevation in the right precordial leads.

ECG repolarization syndrome abnormalities (J wave syndromes) and idiopathic ventricular fibrillation: diagnostic and management

Early repolarization (ER) pattern has been recognized for several decades and was interpreted as a variant of the normal electrocardiogram (ECG) as it was frequently observed in young healthy subjects or athletes. It is characterized by a J point elevation and ST-segment elevation inscribed as a QRS slurring or a notch of the S wave in the inferior leads or/and the lateral leads. The ER pattern has been the subject of increased interest since the report of its higher prevalence in subjects resuscitated from cardiac arrest related to idiopathic ventricular fibrillation (VF). Furthermore, population-based studies showed in healthy young adults that ER pattern was associated with an increased cardiovascular mortality and total mortality. A relationship between ER pattern and malignant arrhythmias is also supported by the experimental work of Antzelevitch et al. which provided the cellular and ionic basis for the J point elevation and its arrhythmogenic potential. The ER pattern may coexist with a number of cardiac or extracardiac conditions such as hypothermia. But this review will focus attention on the "isolated ER pattern" in healthy individuals. Antzelevitch and Yan proposed because of a number of similarities between the "ER syndrome" and the Brugada syndrome to group both syndromes under the heading of "J wave syndromes". The management of ER syndrome (associated with idiopathic VF) is clearly the insertion of an implantable cardioverter defibrillator (ICD). The ER pattern associated with symptoms such as syncope or a familial history of sudden cardiac death requires a complete work-up. Caution should be raised not to generate anxiety in the subject with asymptomatic "isolated ER pattern" as the odds of developing malignant ventricular arrhythmias or to suffer sudden death in this case are extremely low.

First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study

AIMS

First-degree atrioventricular block (AVB) has traditionally been considered a benign electrocardiographic finding in healthy individuals. However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease. We investigated whether first-degree AVB is associated with heart failure (HF) and mortality in a prospective cohort study of outpatients with stable coronary artery disease (CAD).

METHODS AND RESULTS

We measured the P-R interval in 938 patients with stable CAD and classified them into those with (P-R interval ≥ 220 ms) and without (P-R interval <220 ms) first-degree AVB. Hazard ratios (HRs) and 95% confidence intervals were calculated for HF hospitalization and all-cause mortality. During 5 years of follow-up, there were 123 hospitalizations for HF and 285 deaths. Compared with patients who had normal atrioventricular conduction, those with first-degree AVB were at increased risk for HF hospitalization (age-adjusted HR 2.33: 95% CI 1.49-3.65; P= 0.0002), mortality [age-adjusted HR 1.58; 95% CI (1.13-2.20); P = 0.008], cardiovascular (CV) mortality [age-adjusted HR 2.33; 95% CI (1.28-4.22); P= 0.005], and the combined endpoint of HF hospitalization or CV mortality (age-adjusted HR 2.43: 95% CI 1.64-3.61; P ≤ 0.0001). These associations persisted after multivariable adjustment for heart rate, medication use, ischaemic burden, and QRS duration. Adjustment for left ventricular systolic and diastolic function partially attenuated the effect, but first-degree AVB remained associated with the combined endpoint of HF or CV death (HR 1.61, CI 1.02-2.54; P= 0.04).

CONCLUSION

In a large cohort of patients with stable coronary artery disease, first-degree AVB is associated with HF and death.

Risk of sudden death among young individuals with J waves and early repolarization: putting the evidence into perspective

The presence of J waves and ST-segment elevation on the electrocardiogram (ECG), jointly termed "the early repolarization pattern," has traditionally been considered a marker of "good health." However, recent case control series and long-term population studies have established a statistically significant association between this ECG pattern and an increased risk for arrhythmic death. This finding has raised concern among physicians, who now are asked to estimate the "arrhythmic risk" following the incidental discovery of J waves on routine ECG. Therefore, we review the literature linking early repolarization with arrhythmic risk to place this "fear of J waves" in the right perspective. We found five case control studies (involving 331 patients with idiopathic ventricular fibrillation [VF] and 8,649 controls). All of these studies showed that J waves, particularly of large amplitude and recorded in multiple leads, are more prevalent among patients with idiopathic VF. We also found three large population studies (involving >17,000 individuals) looking at the prognostic value of early repolarization. Two of these studies showed that the presence of J waves >2 mm in amplitude in asymptomatic adults is associated with a threefold increased of arrhythmic death during very long-term follow-up. Individuals with J waves do have some degree of increased dispersion of repolarization that places them at increased risk for arrhythmic death, but only in the presence of additional proarrhythmic factors or triggers. A sensible approach for the asymptomatic patient with J waves is proposed.

Heritability of early repolarization: a population-based study

BACKGROUND

Early repolarization (ER), defined by J-point elevation in 12-lead ECG, was recently associated with increased risk for idiopathic ventricular fibrillation and cardiovascular mortality. The determinants of ER are unknown. We investigated its heritability in a large, family-based cohort.

METHODS AND RESULTS

The study sample comprised 1877 individuals from 505 white nuclear families representative of the British general population. Standard 12-lead ECGs were evaluated for the presence of ER, defined as J-point elevation of ≥0.1 mV in at least 2 adjacent inferior (II, III, and aVF) or anterolateral (I, aVL, and V(4) through V(6)) leads. Narrow sense heritability estimates were computed adjusting for age, age(2), and sex. The prevalence of ER was 7.7% (n=145) in the whole cohort, 5.9% (n=56) in parents, and 9.6% (n=89) in offspring. Heritability estimate for the presence of ER was calculated at h(2)=0.49 (standard error=0.14; P=2.7*10(-4)) and was higher when restricted to its presence in inferior leads (h(2)=0.61, standard error=0.18, P=4.3*10(-4)) or for the notching ER morphology (h(2)=0.81, standard error=0.19, P=2.4*10(-5)). Individuals with at least 1 affected parent had a 2.5-fold increased risk for presenting with ER on ECG (odds ratio, 2.54; 95% confidence interval, 1.33 to 4.84; P=0.005). Familial transmission was more frequent when the mother was affected (odds ratio, 3.84; 95% confidence interval, 1.41 to 10.43; P=0.008) than when the father was affected (odds ratio, 1.82; 95% confidence interval, 0.82 to 4.03; P=0.141), although this difference was not statistically significant (P=0.18).

CONCLUSIONS

ER is a heritable phenotype. Offspring of ER-positive parents have a 2.5-fold increased risk of presenting with ER on their ECG.

Short and long QT syndromes: does QT length really matter?

The short and long QT syndromes are inherited diseases associated with an increased risk for life-threatening arrhythmias. The first case of long QT syndrome (LQTS) was reported more than 150 years ago, and the study of this disease led to crucial advancement of our understanding of channelopathies and associated ventricular arrhythmias. Ten years ago, Gussak et al. reported four cases of idiopathic ventricular fibrillation in individuals from a family with a history of sudden cardiac death exhibited very short QT interval and labeled the disease: short QT syndrome (SQTS). Over this decade, the SQTS was found to be a rare inherited syndrome with the potential to provide novel insights into the main mechanisms of cardiac arrhythmogenicity. In this review, we discuss these mechanisms and provocatively question the role of the QT interval duration as a surrogate marker of increased risk for arrhythmia in both the LQTS and the SQTS.

Clinical and mechanistic issues in early repolarization of normal variants and lethal arrhythmia syndromes

Early repolarization, involving ST-segment elevation and, sometimes, prominent J waves at the QRS-ST junction, has been considered a normal electrocardiographic variant for over 60 years. A growing number of case reports and case-control studies indicate that in some instances, early repolarization patterns are associated with increased risk of idiopathic ventricular fibrillation. Epidemiological evidence indicates a dose effect for the risk of cardiac and sudden death with the extent of J-point elevation. This paper reviews present knowledge regarding the epidemiology, presentation, therapeutic response, and mechanisms characteristic of early repolarization. We highlight major unanswered questions relating to our limited ability to determine which individuals with this common electrocardiographic variant are at risk for sudden death, our incomplete understanding of underlying mechanisms, the inadequate information regarding genetic determinants and therapeutic responses, and the unclear relationship between early repolarization and other conditions involving accelerated repolarization and sudden arrhythmic death such as Brugada and short-QT syndromes. This review paper intends to inform the practicing physician about important clinical issues and to stimulate investigators to address the many unresolved questions in this rapidly evolving field.

Early repolarization syndrome – a new electrical disorder associated with sudden cardiac death –

Early repolarization (ER), consisting of a J-point elevation, notching or slurring of the terminal portion of the R wave (J wave), and tall/symmetric T wave, is a common finding on the 12-lead electrocardiogram. For decades, it has been considered as benign, barring sporadic case reports and basic electrophysiology research that suggested a critical role of the J wave in the pathogenesis of idiopathic ventricular fibrillation (VF). In 2007-2008, a high prevalence of ER in patients with idiopathic VF was reported and subsequent studies reinforced the results. This review summarizes the current state of knowledge concerning ER syndrome associated with sudden cardiac death.