Early repolarization is associated with symptoms in patients with type 1 and type 2 long QT syndrome

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Sex-related differences in incidence, phenotype and risk of sudden cardiac death in inherited arrhythmia syndromes

Inherited Arrhythmia Syndromes (IAS) including long QT and Brugada Syndrome, are characterized by life-threatening arrhythmias in the absence of apparent structural heart disease and are caused by pathogenic variants in genes encoding cardiac ion channels or associated proteins. Studies of large pedigrees of families affected by IAS have demonstrated incomplete penetrance and variable expressivity. Biological sex is one of several factors that have been recognized to modulate disease severity in IAS. There is a growing body of evidence linking sex hormones to the susceptibility to arrhythmias, yet, many sex-specific disease aspects remain underrecognized as female sex and women with IAS are underinvestigated and findings from male-predominant cohorts are often generalized to both sexes with minimal to no consideration of relevant sex-associated differences in prevalence, disease manifestations and outcome. In this review, we highlight current knowledge of sex-related biological differences in normal cardiac electrophysiology and sex-associated factors that influence IAS phenotypes.

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.

Latent Causes of Sudden Cardiac Arrest

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

Congenital Long QT Syndrome

Congenital long QT syndrome (LQTS) encompasses a group of heritable conditions that are associated with cardiac repolarization dysfunction. Since its initial description in 1957, our understanding of LQTS has increased dramatically. The prevalence of LQTS is estimated to be ∼1:2,000, with a slight female predominance. The diagnosis of LQTS is based on clinical, electrocardiogram, and genetic factors. Risk stratification of patients with LQTS aims to identify those who are at increased risk of cardiac arrest or sudden cardiac death. Factors including age, sex, QTc interval, and genetic background all contribute to current risk stratification paradigms. The management of LQTS involves conservative measures such as the avoidance of QT-prolonging drugs, pharmacologic measures with nonselective β-blockers, and interventional approaches such as device therapy or left cardiac sympathetic denervation. In general, most forms of exercise are considered safe in adequately treated patients, and implantable cardioverter-defibrillator therapy is reserved for those at the highest risk. This review summarizes our current understanding of LQTS and provides clinicians with a practical approach to diagnosis and management.

Early repolarization in the inferolateral leads predicts the presence of vasospastic angina: a novel predictor in patients with resting angina

BACKGROUND

An association between early repolarization and ventricular fibrillation has recently been reported in patients with vasospastic angina (VSA). However, no studies have clarified whether the presence of early repolarization can predict VSA.

METHODS

Participants comprised 286 patients (136 males) with clinically suspected VSA who underwent intracoronary provocation tests using acetylcholine or ergonovine. Patients were divided into a VSA group [n = 94, positive provocation test as induction of coronary arterial spasm (>90% stenosis)] and a non-VSA group (n = 192). Detailed early repolarization data were compared between groups.

RESULTS

The VSA group showed a higher frequency of smokers (28.7%) than the non-VSA group (17.2%; P = 0.02). On baseline 12-lead ECG, early repolarization (defined as a J-point elevation ≥0.1 mV from baseline in both or either of inferolateral leads) was found in 39 patients (inferior leads, n = 27; inferolateral leads, n = 12). Early repolarization was found more frequently in the VSA group (28.7%) than in the non-VSA group (6.2%, P < 0.01). Multivariate analysis revealed early repolarization as an independent predictor of VSA (odds ratio, 5.22; 95% confidence interval, 2.41-11.2; P < 0.01). Early repolarization pattern features including inferior lead, higher amplitude, notched type and horizontal/descending ST segments were associated with increased risk of VSA.

CONCLUSION

In patients with resting chest pain, early repolarization was a predictor of VSA that could be particularly related to the inferior lead, higher amplitude, notched type and horizontal/descending ST segment.

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.

J-Wave Syndromes: Electrocardiographic and Clinical Aspects

Early repolarization, Brugada syndrome, and pathologic J waves have been described for decades, but only recently experimental and clinical data have allowed reconciliation of Brugada and Early Repolarization under the common definition of J-wave syndromes. The concept was derived from studies showing, in both conditions, the presence of transmural dispersion of repolarization, localized conduction abnormalities, and abnormal transition between QRS and ST segment on electrocardiogram. Although several clinical studies have addressed the clinical presentation and epidemiology of J-wave syndromes, relevant knowledge gaps exist. Incomplete pathophysiologic understanding and uncertain electrocardiographic definitions limit effective risk stratification. Here, we review the current knowledge and recommendations for diagnosis and clinical management of these arrhythmogenic disorders.

J Waves for Predicting Cardiac Events in Hypertrophic Cardiomyopathy

OBJECTIVES

This study sought to investigate whether the presence of J waves was associated with cardiac events in patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

It has been uncertain whether the presence of J waves predicts life-threatening cardiac events in patients with HCM.

METHODS

This study evaluated consecutive 338 patients with HCM (207 men; age 61 ± 17 years of age). A J-wave was defined as J-point elevation >0.1 mV in at least 2 contiguous inferior and/or lateral leads. Cardiac events were defined as sudden cardiac death, ventricular fibrillation or sustained ventricular tachycardia, or appropriate implantable cardiac defibrillator therapy. The study also investigated whether adding the J-wave in a conventional risk model improved a prediction of cardiac events.

RESULTS

J waves were seen in 46 (13.6%) patients at registration. Cardiac events occurred in 31 patients (9.2%) during median follow-up of 4.9 years (interquartile range: 2.6 to 7.1 years). In a Cox proportional hazards model, the presence of J waves was significantly associated with cardiac events (adjusted hazard ratio: 4.01; 95% confidence interval [CI]: 1.78 to 9.05; p = 0.001). Compared with the conventional risk model, the model using J waves in addition to conventional risks better predicted cardiac events (net reclassification improvement, 0.55; 95% CI: 0.20 to 0.90; p = 0.002).

CONCLUSIONS

The presence of J waves was significantly associated with cardiac events in HCM. Adding J waves to conventional cardiac risk factors improved prediction of cardiac events. Further confirmatory studies are needed before considering J-point elevation as a marker of risk for use in making management decisions regarding risk in patients with HCM.

Advances in the diagnosis and treatment of catecholaminergic polymorphic ventricular tachycardia

Since the sentinel description of exercise-triggered ventricular arrhythmias in 21 children, our recognition and understanding of catecholaminergic polymorphic ventricular tachycardia has improved substantially. A variety of treatments are now available, but reaching a diagnosis before cardiac arrest remains a challenge. Most cases are related to variants in the gene encoding for ryanodine receptor-2 (RyR2), which mediates calcium-induced calcium release. Up to half of cases remain genetically elusive. The condition is presently incurable, but one basic intervention, the universal administration of β-blockers, has improved survival. In the past, implantable cardioverter-defibrillators (ICDs) were frequently implanted, especially in those with a history of cardiac arrest. Treatment limitations include under-dosing and poor compliance with β-blockers, and potentially lethal ICD-related electrical storm. Newer therapies include flecainide and sympathetic ganglionectomy. Limited data have suggested that genotype may predict phenotype in catecholaminergic polymorphic ventricular tachycardia, including a higher risk of life-threatening cardiac events in subjects with variants in the C-terminus of ryanodine receptor-2 (RyR2). At present, international efforts are underway to better understand this condition through large prospective registries. The recent publication of gene therapy in an animal model of the recessive form of the disease highlights the importance of improving our understanding of the genetic underpinnings of the disease.

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.