ABC | Volume 111, Nº1, July 2018

Original Article Warpechowski Neto et al Brugada syndrome – cohort and 19-year registry Arq Bras Cardiol. 2018; 111(1):13-18 Methods This is a cohort study of patients referred for electrophysiological study at the ICFUC electrophysiology laboratory between January 1998 and March 2017. Of the 5506 studies performed in that period, 35 (0.67%) corresponded to assessment of patients with electrocardiographic pattern compatible with BrS (Brugada pattern), who were followed up from that study on. The inclusion criteria were: absence of structural heart disease, absence of personal history of aborted sudden death, electrocardiogram (ECG) compatible with type I, II or III Brugada pattern, and electrophysiological study under a preestablished protocol of ventricular stimulation with three baseline cycles (600, 500 and 400 ms) and introduction of up to three extra stimuli. Diagnostic challenge with infusion of class IA antiarrhythmic drugs according to the Vaughan Williams classification (ajmaline at the dose of 1 mg/kg for 10 minutes or procainamide 10 mg/kg for 10 minutes) was performed in type II electrocardiographic presentations, in accordance with the most used drugs in European and American studies. 8 From the electrophysiological study on, the patients were followed up throughmedical appointments at regular six-month intervals, medical record review and/or telephone contact. Statistical analysis Our data bank was stored in Microsoft Excel sheets and analyzed by use of the Statistical Package for Social Sciences (SPSS) software, version 20.0 (Armonk, NY, USA: IBM Corp). The continuous variables were expressed as mean (± standard deviation) and compared by use of independent samples t test. The continuous variables of non-gaussian distribution were expressed as median [interquartile range (IQR)] and compared by using Mann-Whitney U test. The categorical variables were expressed as percentages and compared by use of chi-square test. The comparisons between groups were performed by using z test, with post-hoc Bonferroni analysis to identify the statistical difference. Kaplan-Meyer event-free survival analysis was performed, with percentage survival and standard error. Differences between the frequency of events over time according to the variables identified were compared by use of log-rank test. A p value < 0.05 was considered statistically significant. Follow-up outcomes By use of electronic medical record review or telephone call, the occurrence of the following events was investigated: death, syncope, hospitalization due to arrhythmia, and recurrent palpitations requiring medical care. In patients receiving an implantable cardioverter defibrillator (ICD), the occurrence of shock was investigated, and, when present, the appropriateness (shock due to ventricular arrhythmia) or inappropriateness (shock due to supraventricular tachycardia, increased T-wave sensitivity or electromagnetic interference) of the event was assessed. Results Of the 35 patients included in the cohort, 22 (62.85%) showed a type I electrocardiographic pattern, 12 (34.30%) showed a type II, and 1 patient (2.85%), a type III pattern. Regarding sex, 25 patients (71.42%) were of the male sex. The mean age was 43.89 ± 13.1 years, and most patients (65.71%) were asymptomatic at the time of inclusion. Regarding the symptoms, 6 patients (17.14%) had palpitations, 5 (14.28%) reported syncope, and 3 (8.57%) reported sudden death of a first-degree relative. Sixteen patients (45.7%) had induced ventricular tachyarrhythmias on stimulation – mean refractory ventricular period of 228 ± 36 ms. Eleven patients (31.4%) with type II ECG pattern received ajmaline or procainamide, and 7 of them (63.6%) changed to type I ECG pattern. Table 1 summarizes the clinical, electrocardiographic and electrophysiologic characteristics of the patients included in this study. No difference was observed between the groups with and without induced arrhythmia (Table 2). Sixteen patients (45.7%) received an ICD. Of those patients, only 2 had no arrhythmia triggered (reason for implantation: history of sudden death and syncope). Two patients with ventricular arrhythmia (1 with nonsustained ventricular tachycardia and another with ventricular fibrillation) refused to receive the ICD despite the clinical indication. In a mean follow-up of 5 years, 1 of the 16 patients (6.25%) who received the ICD had appropriate therapy for ventricular fibrillation, and 1 (6.25%) attended no consultation after implantation (Figure 1). No death was reported during follow-up. Four patients (11.4%) had other arrhythmic events, such as episodes of nonsustained supraventricular tachyarrhythmias and frequent premature ventricular complexes. Figure 2 shows the discrimination of events in patients with ICD. Discussion The long-term event rate of patients diagnosed with BrS or electrocardiographic pattern of BrS is little known, because of the relative short time since that syndrome initial description in 1992, 1 in addition to the limited follow-up duration of current studies, most of which no longer than 3 years. Table 1 – Clinical, electrocardiographic and electrophysiological study characteristics Clinical presentations N = 35 Men 25 (71.42%) Age 43.89 ± 13.1 years Asymptomatic 23 (65.7%) Syncope 5 (14.3%) Palpitation 6 (17.14%) Electrocardiographic presentations Type I 22 (62.85%) Type II 12 (34.30%) Type III 1 (2.85%) Electrophysiological study Ventricular tachyarrhythmia 16 (45.7%) Refractory period 228 ± 36 ms HV interval 49 ± 8.6 ms Ajmaline / Procainamide 11 (31.4%) 14