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  • br Demographic and arrhythmia characteristics gender

    2019-06-26


    Demographic and arrhythmia characteristics: gender, circadian pattern of VF, and atrial arrhythmias The prevalence and arrhythmic risk of BS and ERS differ considerably. The BS ECG pattern occurs rarely in the general population, while the ER pattern is a common ECG phenomenon, especially in young men and athletes (Fig. 1). The BS pattern portends a high risk of developing arrhythmias, while the ER pattern portends a relatively low risk of sudden death. In a Japanese Ritodrine HCl study, the prevalence of the typical coved-type BS ECG is estimated to occur in approximately 0.12% of the general population [15]. The odds ratio of sudden unexpected death in this BS ECG group was 52.63, relative to that of control subjects [16]. The prevalence of the ER pattern depends on the definition of ER. When the traditional definition of ER (more emphasis on the ST segment elevation with or without the J wave) is used, the prevalence is approximately 2% [17,18]. When defined as J wave>1mm regardless of the ST segment elevation (a new definition), the prevalence is approximately 5–12% [19–23]. The suggestion that ER may be associated with fatal ventricular tachyarrhythmia (VTA) resulted in considerable confusion in clinics because of the high prevalence of ER in the general population. Over the past several years, numerous case-control and population studies have introduced a renewed concept on the prognosis of individuals with the ER pattern [17–23]. In brief, ER can be categorized into several types. The traditional definition of ER that emphasizes on the ST segment elevation is not associated with adverse outcome [17,18]. The new definition of ER includes J wave with or without ST segment changes. ER with “J wave and rapidly ascending ST segment” is considered a benign variant. However, “J waves with horizontal/descending ST segment” changes have been associated with an increased risk of arrhythmic death [22]. There is confusion because of the marginally increased risk of arrhythmic deaths. Although statistically significant, the absolute value of the risk of arrhythmic death in this group is still extremely low, with an odds ratio of 13.8 for developing idiopathic VF in a case-control study [24] and a relative risk of 1.43 for arrhythmic death in a population study [22]. Before the publication of these studies, ER pattern was regarded as “forme fruste” BS because of their similar electrocardiographic and electrophysiologic background in basic experimental studies [25,26]. Considering the low odds of malignant arrhythmia, it is yet too premature to assume that all the subjects with ECG ER pattern (even those with the malignant form of ER) require medical attention for a risk of SCD. Both ERS and BS show a strong male preponderance. In papers published on BS, men account for approximately 70–90% of patients. In the experimental model of canine wedge preparation, the spike-and-dome morphology of the action potential (AP) was more prominent in the male than in the female dog preparations [27]. The prominent epicardial notch was caused by higher ITo density in the male ventricular epicardial cells than in the female preparations. This provides the electrophysiologic background for male dog wedges to develop tachyarrhythmias (phase 2 reentry) in response to class IC antiarrhythmic agents, the combined blockade of Na+ and Ca2+ currents induced by terfenadine or increased outward K+ current induced by pinacidil [27]. This difference in AP morphology is thought to underlie the gender-associated differences in the prevalence of ER pattern in the general population. The difference in ventricular AP morphology observed between male and female subjects may be related to the presence of different sex hormones. Experiments in ovariectomized rats show that estrogen may be involved in one of the mechanisms responsible for the reduction in Kv4.3 expression and function in the myometrium. Testosterone has been reported to shorten the AP duration by enhancing slowly activating delayed rectifier K+ current (IKs) and suppressing the L-type Ca2+ current (IcaL) [28]. Shimizu et al. showed a strong positive association between BS and higher testosterone levels (hypertestosteronemia) and a strong inverse association between BS and body mass index [29]. The disappearance of the Brugada phenotype after surgical castration is a direct evidence of the role of sex hormones. Typical Brugada-type ECG patterns that had persisted over several decades were eliminated after surgical castration [30]. In addition, it was reported that electrocardiographic ST segment levels were significantly decreased after androgen-deprivation therapy, which suggests that testosterone may modulate the early phase of ventricular repolarization, as seen in patients with BS and ERS [31].