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Since its first clinical evidence in 2008, there have been only few clinical reports of ablation in early repolarization syndrome (ERS). What is still undetermined is whether the mechanism of the ablation effect is due to the suppression of the trigger or substrate modification. In idiopathic ventricular fibrillations (VFs), the triggering sources mainly arose from either the Purkinje system or, less commonly, from the ventricular muscle. In ERS, VF sources from right or left Purkinje tissue are dominant (83%), with the site of origin correlating with the electrocardiographic location of early repolarization. RF catheter ablation of ERS is feasible and can be used as a bailout therapy for drug-refractory VF storms. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

The role of an implantable cardioverter–defibrillator (ICD) in patients with ERS still needs to be considered, since there have been no prospective, randomized studies that have examined the effect of ICDs compared with antiarrhythmic drugs in patients with ERS and ventricular fibrillation (VF). However, theoretically, ICDs must be the first-line strategy for patients with ERS because ICDs are effective in patients with a high risk of sudden cardiac death, regardless of underlying heart disease. An essential problem of ICDs is that they cannot prevent the occurrence of tachycardia attacks, and this limits their clinical usefulness. Especially during an electrical storm, it induces multiple shocks to terminate VF and may deteriorate the patients’ outcome. Another unresolved problem of ICDs is inappropriate therapy which demonstrated a 10–20% incidence in the previous large clinical trials. To program relatively high tachycardia detection rate and long detection rate are possible strategy to reduce risks of inappropriate and unnecessary ICD shocks. Another attractive capability of ICD is that it stores electrograms during the episode of VF. Analyzing the mode of onset or electrocardiographic manifestations at the episodes of ventricular arrhythmia is an effective strategy to clarify the underlying mechanism of ER and VF.

Although early repolarization has generally been considered benign for decades, there is increasing evidence that early repolarization is associated with an increased risk of ventricular fibrillation and sudden cardiac death. Early repolarization pattern in the inferior and/or lateral leads has recently been associated with increased risk of sudden cardiac death, and early repolarization syndrome has been proposed as a new entity of idiopathic ventricular fibrillation. Diagnostic criteria for early repolarization syndrome proposed in the expert consensus statement is available, but there are still some controversies about the diagnosis. Early repolarization syndrome shares clinical characteristics with Brugada syndrome, but the unique characteristics may be helpful for diagnosis and risk stratification.

Early repolarization (ER) is a common electrocardiographic finding characterized by elevation of the J point with notching or slurring on the electrocardiogram (ECG) followed by ST-segment elevation. Although this condition has been considered benign, Haissaguerre et al. demonstrated that patients with J waves in the inferolateral leads were likely to be associated with idiopathic ventricular fibrillation (VF) and reported this entity as inferolateral early repolarization syndrome (ERS) in 2008. Brugada syndrome (BrS) is another clinical entity that causes sudden death due to VF in patients with apparently structurally normal hearts and is characterized by coved ST-segment elevation in the right precordial leads. ERS and BrS are considered to share a similar genetic background and to represent a continuous spectrum of phenotypic expression. However, the exact pathophysiological mechanisms underlying ERS and BrS remain unknown, and some clinical manifestations reportedly differ between these syndromes. In this chapter, we introduce our current understanding of ERS and BrS.

In patients with early repolarization syndrome (ERS), pharmacological therapy may be necessary in patients with frequent delivery of shocks from implantable cardioverter-defibrillator (ICD) due to ventricular fibrillation (VF). In cases of electrical storm, intravenous isoproterenol infusion has been shown to be most effective. Isoproterenol seems to be effective in restoring the action potential dome in the epicardium, because it markedly increases ICa secondary to elevation of intracellular levels of cyclic AMP. It is also effective by indirect suppression of Ito due to its ability to increase the heart rate. Following acute phase, oral quinidine has been reported to prevent the recurrence of VF. Quinidine is a class I antiarrhythmic agent. However, it potently blocks Ito, leading to the restoration of the action potential dome, a normalized ER, and prevents the occurrence of VF. An alternative therapy may be the administration of cilostazol and its combination with bepridil.

The early repolarization pattern and J wave were recognized during the very early period after the invention of the ECG. While the J wave has been reported to become prominent in particular circumstances, i.e., hypothermia, hypercalcemia, and brain damages, early repolarization has long been considered to be a benign finding, which is attributable to the definition of early repolarization during the period that included not only end-QRS notching/slurring but also ST segment elevation continuing to the upward concave ST segment and tall T wave. The prevalence of an early repolarization pattern and its predictive value has varied widely among the studies published more recently, which presumably were due to the diversity of the definitions. In the reports, either in case control studies or population studies, showing an association between an early repolarization pattern and cardiac or arrhythmic death, the definition has been based on J point elevation with notched or slurred J wave in the inferior or lateral leads, while early repolarization based on ST segment elevation seldom has shown any increased risk. The accumulated evidence has also demonstrated that even in those with J point elevation, the arrhythmic risk does not increase with a concave ST segment morphology. The definition of an early repolarization pattern should be unified and standardized to better stratify the risk of arrhythmic death.