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 follow-up, with higher risks for patients induced with one or two extra stimuli. 18 The overall analysis of data indicates that the electrophysiological study is useful, mainly in patients at intermediate risk, to whom the clinical characteristics cannot provide a dichotomous classification of high or low risk. In 2017, Sieira et al. 19 proposed a model of risk classification based on a cohort of 400 patients from a single Belgian center, with mean age and percentage of asymptomatic individuals similar to those of our cohort, in which the clinical factors associated with outcomes were categorized into a score model including the following variables: type I electrocardiographic pattern, history of sudden death of a first-degree relative younger than 35 years, arrhythmia induced on electrophysiological study, syncope, sinus node disease and history of sudden death. In the model proposed, a score equal to or greater than 2 represents high risk for outcome, with positive predictive value of 90%, maintained at 81% when having external validity. In the present study, the rate of the implantable device events was lower than that reported in the literature, including national studies with patients with BrS, 20 and the one patient with appropriate therapy received it in the first year of follow-up. Nevertheless, the mean 5-year follow‑up showed a temporal gain as compared to many similar studies, allowing for the analysis of events in a larger time window – knowing that the risks are continuous throughout life – with the potential advantage of overcoming occasional inaccurate clinical data, manly family history, because the information is patient-dependent and previous data might not be well characterized in the generation immediately before the proband. Although controversial, the use of electrophysiological study for stratification has shown to be a useful tool to identify high-risk patients, representing a clear signal that the ventricle is more excitable, and, thus, prone to arrhythmic events. 21 Limitations This study has limitations such as the fact that the cohort is not constituted by patients identified by ECG, but by those, who, according to their attending doctors would benefit from an electrophysiological study for risk stratification, a fact that limited the sample size and can be a bias by selecting patients that raise more concern about future events. Another fact is that, of the 35 patients, 5 did not undergo follow-up at the same institution where the electrophysiological study was performed. In such cases, data were limited to information collected via telephone, with checking up on neither the electronic medical records nor the devices. Moreover, we performed no genetic study of the population assessed, because it is not routinely available in the healthcare system in addition to its costs. Conclusion Brugada syndrome is a potentially fatal arrhythmic condition, and reports on it increased substantially in past years. In this cohort, similarly to the world literature, most patients are of the male sex and had spontaneous type I electrocardiographic pattern. Class IA antiarrhythmic drugs of the Vaughan Williams classification have high rates of electrocardiographic conversion when used for diagnostic challenge. The rate of arrhythmic event was 6.25%, and mortality was lower than that in the literature. The electrophysiological study for risk assessment, although controversial, is currently a useful tool for patient’s stratification, mainly when the clinical characteristics are poor and do not allow for estimating accurately the risks of future events. Author contributions Conception and design of the research, Acquisition of data, Analysis and interpretation of the data, Statistical analysis, Obtaining financing, Writing of the manuscript and Critical revision of the manuscript for intellectual content: Warpechowski Neto S, Lima GG, Ley LLG, Ley ALG, Dutra LZ, Pires LM, Kruse ML, Leiria TLL. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This study is not associatedwith any thesis or dissertationwork. Ethics approval and consent to participate This study was approved by the Ethics Committee of the Instituto de Cardiologia do Rio Grande do Sul under the protocol number UP 5374/17. All the procedures in this study were in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study. 17