ABC | Volume 112, Nº3, March 2019

Editorial Scanavacca Programmed ventricular stimulation in the management of BrS patients Arq Bras Cardiol. 2019; 112(3):217-219 whereas in the second condition, a milder substrate would be found, and hence the possibility of malignant arrhythmias would be lower, detected only in very special conditions. In this case, the substrate would be only identified by analysis of electrograms obtained from the epicardial surface or by infusion of potent sodium-channel blockers. In line with this hypothesis, recent studies on radiofrequency catheter ablation of the subepicardial substrate in BrS have shown that the induction of SVT or VF is common in patients with spontaneous type 1 pattern; these arrhythmias became noninducible after ablation of the arrhythmogenic substrate with normalization of the typical pattern. 11,13 The extension of the BrS substrate at the moment of the ES could then explain the differences in the results reported in several clinical studies and current controversies. 14 Therefore, patients with BrS recovered from cardiac arrest or patients with persistent type 1 electrocardiographic pattern would have a higher rate of induction of ventricular arrhythmias as comparedwith thosewithout electrocardiographicmanifestations. However, so far, there is not enough information regarding the EKG presentation at the time of the electrophysiological study. 15 The first study to use programmed ventricular stimulation for screening of asymptomatic BrS patients for ICD implantation involved 252 patients; 116 of them had a history of syncope or had recovered from cardiac arrest, and 136 were asymptomatic at diagnosis. Polymorphic ventricular tachycardia or VF were induced in 130 (51%) patients. induction of ventricular arrhythmias was more frequent (73%) in sympomtatic than asymptomatic (33%) patients (p=0.0001). Spontaneous arrhythmic event occurred in 52 individuals (21%) in a mean follow-up of 34 ± months, 45 (39%) of 116 symptomatic patients and 7 (5%) of 136 asymptomatic patients. On the other hand, only 1 patient in 91 (1.1%) of the asymptomatic group presented spontaneous arrhythmic event when the ventricular pacing was negative. 15 These data were corroborated by a second study by the same group, in which patients were followed for up to 20 years. Induction of SVT/VF in the ES had a sensitivity of 75% and specificity of 91.3% for spontaneous occurrence of malignant arrhythmias in asymptomatic patients. Despite the low positive predictive value (18.2%), the procedure had a negative predictive value of 98.3%. 16 Clinical studies by other authors did not reproduce these findings, generating a debate that persists up to the present days. The PRELUDE was a multicenter prospective study including 273 asymptomatic patients. During the clinical follow-up, with a median of 34 months, there was no significant difference in the rates of events between patients with and without induced ventricular arrhythmias in the ES. 17 In the FINGER BrS registry involving 654 asymptomatic patients, followed by 31.9 (14 to 54.4) months, there was a low rate of events (0.5%). Although this rate was higher in patients with induced ventricular arrhythmias in the ES, there was no statistical significance in the multivariate analysis. 18 In the meta-analysis by Kusumoto et al., 2 organized by the AHA/ACC/HRS, six studies on BrS patients were selected of a total of 236 titles retrieved from traditional databases. To minimize possible patient overlap, the primary analysis included five of six studies selected, with exclusion of one study conducted in the same institution. Of 1,138 patients included, SVT or sustained VF was induced in 390 (34.3%) with occurrence of major arrhythmic events (SVT, VF, cardiac MS or appropriate ICD therapy) in 13 (3.3%) patients, compared with 12 events (1.6%) in 748 patients without induced arrhythmia, resulting in an odds ratio (OR) of 2.3 (95%IC: 0.63-8.66; p = 0.2). A second analysis included all six studies, with potential data duplication. Of 1,401 patients, 481 (34.2%) had SVT or VF induced in the ES. In patients with induced SVT/VF, there were 23 arrhythmic events (5.0%), whereas among those without SVT/VF induction, 14 events occurred (1.5%), resulting in an OR of 3.3 (95%CI: 1.03–10.4; p = 0.04). Based on these data, the 2017 AHA/ACC/HRS guidelines issued a 2B recommendation with level of evidence B for indication of ES to asymptomatic BrS patients, using less aggressive ventricular stimulation protocols when performed (up to two extrastimulation). 2 In summary, these data do not establish the real role of SVT/VF induction in asymptomatic patients with BrS, probably due to the lack of homogeneity of samples and methods used in the studies. These data also indicate the need for prospective, multicenter studies involving a larger number of patients. 1. Halperin JL, Levine GN, Al-Khatib SM, Birtcher KK, Bozkurt B, Brindis RG, et al. Further evolution of the ACC/AHA clinical practice guideline recommendation classification system: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2016;67(13):1572-4. 2. European Heart Rhythm Association; Heart Rhythm Society, Zipes DP, Camm AJ, Borggrefe M, Buxton AE, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/ American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death). J Am Coll Cardiol. 2006;48(5):e247-346. 3. Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.. J Am Coll Cardiol. 2018;72(14):e91-220. References 218