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    • In contrast the prevalence of BS

    2019-05-16

    In contrast, the prevalence of BS or Brugada-type ECG in Asian countries is relatively high. Type 1 ECG has been identified in 0.17% of 3907 asymptomatic Filipinos [24] and in 0.13% of 20,652 Taiwanese patients who visited the hospital for non-cardiovascular reasons [25]. Brugada-type ECG has been observed in 0.9% of 10,867 young, healthy Korean men [26]. At a glutathione peroxidase rhythm clinic in Singapore, 12 of 392 male patients (3.1%) showed type 1 ECGs and 28 (7.1%) showed Brugada-type ECGs [27]. In Pakistan, the Brugada-type ECG pattern frequency was reported to be 0.8% [28]. The prevalence of BS in the southern Turkish population seems to show an intermediate value compared to that in Asian and Western countries. Bozkurt et al. reported that one of 1238 subjects (0.08%) demonstrated a type 1 ECG and five (0.74%) showed type 2 or 3 ECGs [29]. Overall, the prevalence of BS in adults is estimated to be around 0.15% in Asian countries, including Japan, between 0.1% and 0.02% in Middle Eastern countries, and less than 0.02% in Western countries. As for the reason why the prevalence is high in Asian people, it has been reported that common ethnic-related genetic polymorphisms might modulate the activity of the primary disease-causing mutation or influence susceptibility to arrhythmia. Bezzina et al. identified a haplotype variant consisting of six individual DNA polymorphisms, designated haplotype B, in near-complete linkage disequilibrium within the proximal promoter region of the SCN5A gene in Asians only and not in Caucasians or African-Americans [30]. They concluded that haplotype B does not give rise to BS, but it likely contributes to a higher incidence of BS in the Asian population.
    Incidence of Brugada syndrome in Japan Matsuo et al. reported that the incidence of Brugada-pattern ECG, including coved and saddleback ST elevation ≥1mm was 14.2 persons per 100,000 person-years in a 40-year survey of 4788 atomic bomb survivors <50 years of age in Nagasaki [11]. This rate was nine times higher among men than women (31.4 vs. 3.5 persons, respectively, per 100,000 person-years), and the average age at presentation was 45±10 years, although the peak incidence was observed in patients in their thirties.
    Gender difference in Brugada syndrome Despite the equal genetic transmission of the mutation between the sexes, the clinical phenotype is much more prevalent in men than in women. In Japan, community-based population studies have revealed that Brugada-pattern ECGs (coved or saddleback ST elevation ≥1mm) predominate in men (>90%). Miyasaka et al. reported that the prevalence in men was 0.38% in contrast to 0.03% in women [8]. In another cohort study in which 41% of the subjects were men, the percentage of men with Brugada-pattern ECG was 84% [11]. On the other hand, men with Brugada-pattern ECG comprised 97% of all Brugada subjects in a cohort study that included 79% men [13] and 100% in a study that included 89% men [10]. Tsuji et al. reported that the frequency of men with type 1 ECG was 84% in a survey in which 26% of all ECGs were obtained from men [9]. The data from multicenter BS registries indicate that the frequency of men with type 1 ECG was 94–96% [31,32]. Therefore, the sex-adjusted rate of type 1 ECG in adult men probably reaches 90–96% in Japan. The frequency of boys in the first grade with Brugada-pattern ECG was reported to be 50% [14] (two in 11,282 boys vs. two in 10,662 girls), but it became 90% after the fourth grade [15]. Regarding this gender difference in BS, Di Diego et al. suggested a cellular basis for the male predominance in BS using arterially perfused canine right ventricular (RV) wedge preparation [33]. They reported that the Ito-mediated phase 1 action potential notch in the RV epicardium, which was larger in male dogs than in female dogs, was responsible for the male predominance of the Brugada phenotype. Shimizu et al. suggested that the level of the male hormone, testosterone, which is reported to increase the outward potassium currents, was significantly higher and body mass index (BMI) was significantly lower in men with Brugada than in the controls [34]. In addition, Tsuji et al. reported that the BMI of subjects with the Brugada-pattern ECG was significantly lower than that of subjects without BS in a study with a large number of subjects [9]. The fact that the testosterone levels in males peak during the teen and early adult years and the incidence of Brugada-pattern ECG peaks in the thirties [11], even though the genders show a similar prevalence in childhood [14], may suggest that gender differences are linked to the testosterone level depending on age.