Ajmaline-induced epsilon wave: as a potential interim risk factor between the spontaneous- and drug-induced type 1 Brugada electrogram?

We read the two risk stratification articles in Brugada syndrome (BrS) patients with a great interest by Delise et al.1 the article about the prognosis the prognosis is fairly good in patients with the BrS type 1 electrocardiogram (Br type 1 ECG) without prior sudden cardiac arrest (SCA) who do not undergo implantable cardioverter-defibrillator (ICD) implantation, and by the Takagi et al.2 about the stimulation protocol with a single extra-stimulus might be useful in stratifying risk in BrS patients with spontaneous type 1 ECG and syncope. We want to address some points that merit more attention. Although the BrS entity has been described more than 20 years ago, the prognosis, risk stratification, and management of asymptomatic individuals remain the most controversial issues. Whereas the early identification of at-risk individuals is crucial to prevent a lethal episode, the overtreatment by ICD implantation is another problem in daily clinical practice. Patients with the Br type 1 ECG without previous aborted SCD who do not undergo prophylactic ICD implantation constitute a large population. The current ESC guidelines recommend ICD implantation in patients with a Br type 1 ECG pattern if they have suffered a previous resuscitated SCA (Class I recommendation) or if they have syncope of presumed cardiac origin (Class IIa recommendation). Implantable cardioverter-defibrillator therapy is an effective therapy in high-risk patients with BrS. However, it is also associated with a significant risk of device-related complications. In clinical practice, however, many other patients undergo ICD implantation despite the suggestions of the guidelines since the many cardiology centres adopt an aggressive treatment in subjects with a Brugada type 1 ECG pattern who are not at high risk. Recently, the only 75% of patients who exhibited an arrhythmic event after receiving a prophylactic ICD complied with the HRS/EHRA/APHRS expert consensus statement in 2013 Class II indications, suggesting that efforts are still required for improving risk stratification.3 Conflicting results have been suggested from international registries, which enrolled non-consecutive cases, studied with different programmed electrical stimulation protocols.4 Indeed, the surviving cells surrounded by fibrosis has demonstrated to be responsible of slow conduction and re-entry in inhomogeneous scars detected by as delayed or isolated electrograms, fragmented, late potentials or diastolic electrograms. It has been reported that the baseline fragmented QRS increased major arrhythmic events up to three-fold. However, it is well known that these diagnostic features can be concealed or can fluctuate even to the point of complete normalization.5 Moreover, it has been reported that not all patients with a drug-induced BrS type1 are at low risk of future events; the Ajmaline might unmask not only typical type 1 ST elevation in diagnosis but also concealed electrocardiographic slow conduction features (Figure 1); therefore, we consider that it drug-induced fragmented or epsilon waves as an interim risk stratification tool between the spontaneous- and drug-induced BrS type 1 ECG would have a potential role in risk stratification of asymptomatic BrS patients and would like to hear authors opinions about its potential role of risk stratification of asymptomatic patients. The 12 lead electrocardiogram shows the incomplete RBBB before the Ajmaline test and the classical type 1 Brugada ST elevation in V1 and an epsilon wave in V2 after Ajmaline test. Conflict of interest: none declared.