Author + information
- Pattara Rattanawong, MD,
- Tachapong Ngarmukos, MD∗ (, )
- Eugene H. Chung, MD,
- Wasawat Vutthikraivit, MD,
- Prapaipan Putthapiban, MD,
- Weera Sukhumthammarat, MD,
- Prin Vathesatogkit, MD and
- Piyamitr Sritara, MD
- ↵∗Division of Cardiology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, 270, Rama VI Road, Bangkok, Thailand 10400
Brugada syndrome is an inherited arrhythmic disease associated with sudden cardiac death. The clinical manifestations of Brugada syndrome vary and include ventricular fibrillation, ventricular tachycardia, sudden cardiac death, syncope, nocturnal agonal respiration, palpitations, or chest pain. The symptoms usually present before the 4th decade of life. The Brugada electrocardiogram (ECG) pattern (BrP) is characterized by coved type (type-1 BrP) ST segment elevation ≥2 mm in right precordial leads and saddleback type (type-2 BrP) (1).
The prevalence of type-1 BrP has been reported from Asian and Southeast Asian countries to be between 0.15% and 0.27% (1). However, the prevalence of BrP from a population-based study in Thailand has not been reported.
In this study, we evaluated the prevalence of BrP in Thailand from the Electricity Generating Authority of Thailand (EGAT) study, which is a population-based longitudinal cohort study to identify cardiovascular risk factors in Thailand (2). The Ethics Committee of studies involving human subjects of the Faculty of Medicine Ramathibodi Hospital, Mahidol University, approved the study.
Baseline and follow-up ECGs from patients enrolled in the EGAT cohort study from 2009–2014 (n = 2,584) were retrospectively analyzed by 2 cardiac electrophysiologists. A third cardiologist adjudicated any disagreements. Basic characteristics were compared between type-1 BrP, type-2 BrP, and non-BrP subjects. Those with incomplete data collection (n = 23), no ECG (n = 47), and poor baseline ECG (n = 68) were excluded from our study. Statistical analyses were performed using SPSS 23.0 software (IBM Corp, IBM SPSS Statistics for Macintosh, Version 23.0. Armonk, New York). Confidence interval was calculated by Wilson’s procedure (3).
The study group thus consisted of 2,446 subjects (74.3% males; mean age 40.8 ± 7.0 years). Ten subjects from initial ECG screening in 2009 were diagnosed with type-1 BrP (prevalence: 0.41%; 95% confidence interval [CI]: 0.21% to 0.78%). Twenty-one subjects (0.86%; 95% CI: 0.58% to 1.38%) had type-2 BrP. In males, the prevalence of type-1 BrP and type-2 BrP were 0.55% (95% CI: 0.28% to 1.05%) and 0.83% (95% CI: 0.48% to 1.40%), respectively. Basic characteristics and ECG parameters of type-1 BrP and type-2 BrP subjects are shown in Table 1. The mean age of type-1 BrP subjects was higher when compared to type-2 BrP and control groups. Interestingly, hypertension was more common in type-1 BrP subjects. The frequencies of cardiac symptoms (syncope, palpitations, or chest pain), acute coronary syndrome, and history of other heart disease in first-degree relatives were similar between type-1 BrP, type-2 BrP, and control groups. One of the symptomatic type-1 BrP patients has been managed with an implantable cardioverter-defibrillator since 2012 but no arrhythmias have been recorded. There were no documented episodes of ventricular fibrillation, ventricular tachycardia, sudden cardiac death, or deaths in either the type-1 BrP or type-2 BrP groups after 5 years. One subject from each of the type-1 BrP and type-2 BrP groups was lost to follow up but confirmed alive by Ministry of Public Health records. Two subjects from the type-1 BrP group had no ECGs at follow up. Two of the 7 type-1 BrP subjects with follow-up ECGs had persistent type-1 BrP, whereas the other type-1 BrP subjects revealed a type-2 BrP (2 subjects) or normal ECG (3 subjects). Interestingly, 11 more subjects were later identified with a type-1 BrP (cumulative prevalence: 0.86%; 95% CI: 0.55% to 1.34%) at the 5-year follow-up visit.
Our study is not without limitations. By using a retrospective ECG database, we were unable to diagnose individuals with definitive Brugada syndrome since genetics, electrophysiology studies, and drug provocation tests could not be performed. We also do not have imaging such as echocardiography to rule out structural heart disease.
In conclusion, we have found a higher prevalence of type-1 BrP in the Central Region of Thailand than reported in other Asian countries. Larger multicenter studies of prevalence, ECG screening, risk stratification and management of type-1 BrP should be explored.
Please note: This work was supported by the Cooperative Research Network (CRN) scholarship, the project for Higher Education Research Promotion and National Research University Development, Office of the Higher Education Commission, Ministry of Education, Thailand, and The Thailand Research Fund. Dr. Ngarmukos is a speaker for Boston Scientific, Medtronic, St. Jude Medical, Johnson & Johnson, Bayer, and Daiichi-Sankyo. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors express their gratitude to all EGAT research staffs, especially Miss Nisakron Thongmung, as well as the Office of Research Academic and Innovation, Faculty of Medicine Ramathibodi Hospital, for providing ECG and subjective data.
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