ABC | Volume 112, Nº3, March 2019

Editorial Programmed Ventricular Stimulation in the Management of Brugada Syndrome Patients Mauricio Ibrahim Scanavacc a and Denise Tessariol Hachul Instituto do Coração (Incor), São Paulo, SP – Brazil Mailing Address: Mauricio Ibrahim Scanavacca Av. Joaquim C. A. Marques, 1205. Postal Code 05688-021, Morumbi, SP – Brazil E-mail: mibrahim@cardiol.br , mauricio.scanavacca@gmail.com Keywords Brugada Syndrome; Tachycardia, Ventricular; Ventricular Fibrillation; Death, Sudden, Cardiac/prevention & control; Risk Factors; Defibrilators, Implantable/utilization. DOI: 10.5935/abc.20190047 Since 1980, the American College of Cardiology (ACC) and the American Heart Association (AHA), by means of a systematic methodology, have incorporated and adapted scientific evidence into practical recommendations aiming to improve preventive and therapeutic measures for cardiovascular diseases. These guidelines have become the current reference for cardiology practices and been adopted by many societies, which adapt them according to local realities. 1 In 2006, the AHA/ACC, together with the Heart Rhythm Society (HRS), published the first guidelines for the management of patients with ventricular arrhythmias and prevention of sudden death (SD). In 2017, this first document was updated by the same societies and published in October 2018. 2,3 Despite considerable advances in knowledge of risk stratification, prevention and treatment of SD, many gaps in its understanding still exist. Among many issues raised by the authors of the last review, two were addressed by an independent commission and recently published in an additional document. 4 One of the issues is the subject of the present editorial and refers to the role of the electrophysiological study in risk stratification of asymptomatic patients with Brugada syndrome (BrS). BrS was described in 1992 in individuals with structurally normal hearts who had recovered from a cardiac arrest from ventricular fibrillation showing a unique electrocardiographic pattern, characterized by a right bundle-branch block with ST-segment elevation in the right precordial leads V1 -V3. 5 In the last 25 years, several clinical studies have shown that the BrS is a genetically determined disease, affecting one in 2,000 – 10,000 individuals with apparently normal hearts. The risk of SD is knowingly high in patients who had already had arrhythmic syncope or had recovered from cardiac arrest. There is a consensus that implantation of an automated implantable cardioverter defibrillator (ICD) is the most effective method to prevent SD in these patients. 6 On the other hand, the risk of SD is apparently low in asymptomatic BrS patients, which makes the decision-making about the use of ICD in these patients difficult. Besides, most of these patients are young and at risk of receiving inappropriate shocks, and experience technical problems with generators and electrodes over the years. 7 Several clinical, familial, electrophysiological and genetic aspects have been investigated in attempt to determine the risk of SD in asymptomatic individuals with BrS, who may benefit from an early ICD implantation. However, the discriminating ability of these methods is still a matter of controversy. 6,8 Sustained ventricular tachycardia (SVT) induced by programmed ventricular stimulation (PVS) has been used for many years to identify patients at risk of spontaneous occurrence of SVT/ventricular fibrillation (VF) in patients with structural heart diseases, who may benefit from a prophylactic use of ICD. 2,3 This approach was based on the efficacy of the method in reproducing SVT in a laboratory setting. 9 Clinical observations have revealed that the capacity of the planned ventricular stimulation in reproducing ventricular arrhythmias, particularly SVT, is very high in the chronic phase of myocardial infarction, lower in non-ischemic heart diseases, and almost absent in cardiac channelopathies. 2,3,9 This distinctive behavior is explained by characteristics of the arrhythmogenic substrate in sustained ventricular arrhythmias. In structural heart diseases, it depends on reentries into stable anatomic substrates, mostly represented by scars caused by diseases. Conditions that cause dense myocardial scars with preserved myocardial tissue channels favor the occurrence of reproducible SVTs. In contrast, EP has low reproducibility in conditions where these characteristics are not present. 9 Therefore, the initial suggestion of using PVS for risk stratification of SD in patients with BrS caused surprise among traditional electrophysiologists, 10 since BrS was until then considered a channelopathy without anatomic substrate based on gadolinium-enhanced magnetic resonance. Subsequent studies revealed that BrS patients have an arrhythmogenic substrate characterized, by invasive electrophysiological mapping, by late electrical potential, identified predominantly in subepicardial fibers in the right ventricular outflow tract. 11 Although in some cases, these electrical features have been associated with persistent anatomical changes, 12 in most of the cases, electrophysiologic changes are transient, modulated or induced by hormonal, autonomic, metabolic and drug-related conditions. 6 This could explain why patients with persistent, spontaneous type 1 Brugada electrocardiographic pattern have higher risk of events compared with patients in whom the BrS pattern occurs occasionally. 5 The possible explanation for that is the fact that, in the former patients, the arrhythmogenic substrate is more extensive and stable, detectable in the ECG, and thereby more suitable to SVT and VF in external modulation, 217