br Clinical characteristics Brugada syndrome is
Clinical characteristics Brugada syndrome is more common in Southeast Asia, including Japan, with an estimated prevalence of 12 in 10,000 individuals, compared with Western countries where the estimated prevalence is 1 to 5 in 10,000 individuals. However, the incidence of early repolarization syndrome and the regional variation in incidence are not known . In both Brugada and early repolarization syndromes, the age at diagnosis is around 40 years, and 70% to 80% of patients are men (Table 1).[14–17] A family history of unexplained sudden death is present in 20% to 30% of patients with Brugada syndrome and in 10% to 20% of patients with early repolarization syndrome [14–17]. In Brugada syndrome, arrhythmia events resulting from ventricular fibrillation mainly occur during sleep, while resting, or after meals . However, cardiac arrest occurs during sleep in only 19% and 26% of patients with early repolarization syndrome in the reports by Haissaguerre et al.  and us,  respectively, and also occurs during physical exertion in 9% to 19% of patients. The frequency of arrhythmia recurrences in survivors of ventricular fibrillation or cardiac arrest seems similar; the annual incidence of ventricular fibrillation is 7% to 8% in patients with Brugada syndrome and 6% to 7% in those Anisomycin with early repolarization syndrome [14–17]. In addition to their susceptibility to ventricular fibrillation, atrial fibrillation has also been found in 10% to 20% of patients with Brugada syndrome and in 23% of patients with early repolarization syndrome [17,19].
Electrophysiological characteristics In the 12-lead ECG, Brugada syndrome is characterized by a unique “coved-type” J-point and ST-segment elevation in the right precordial leads V1 to V3, whereas early repolarization syndrome is characterized by an elevation of the J-point, either as QRS slurring or notching of ≥0.1mV in ≥2 consecutive inferior leads (II, III, and aVF) or lateral leads (I, aVL, V5, and V6). However, the diagnostic criteria for early repolarization syndrome, such as the morphology and amplitude of J-point elevation, are still controversial . However, in early repolarization syndrome, J-point elevation in the right precordial leads can also be found in up to ∼20% of patients (Table 2), [17,20] and early repolarization appearing globally in the inferior, lateral, and right precordial leads has been associated with the highest risk of ventricular fibrillation [12,20]. Similarly, the presence of inferolateral early repolarization is associated with an increased risk of arrhythmia events in patients with Brugada syndrome. In both Brugada and early repolarization syndromes, the characteristic electrocardiographic changes are dynamic, and the amplitude and the existence of the characteristic J-point/ST-segment or early repolarization varies. J-point elevation becomes most prominent just before the development of ventricular fibrillation, supporting the arrhythmogenicity of J-point abnormalities [6,11]. Both syndromes share pause- and bradycardia-dependent augmentation of the J-point amplitude (Figure), which has been suggested useful in distinguishing persons with an increased risk of arrhythmia events from those with benign early repolarization . Because the electrocardiographic changes can occasionally disappear, efforts to provoke electrocardiographic changes have been attempted. In Brugada syndrome, sodium channel blockers are used to detect the diagnostic Brugada electrocardiographic pattern. However, sodium channel blockers attenuate J-point elevation in early repolarization syndrome, and to date, there is no established test for the diagnosis . Fig. 1 Conduction abnormalities at the His–Purkinje system and the right ventricular outflow tract are sometimes evident in Brugada syndrome. In our recent report, the PR interval and QRS duration are also longer in patients with early repolarization syndrome than in matched controls (Table 2) . Table 3 shows a comparison of the electrocardiographic parameters between patients with early repolarization syndrome and those with Brugada syndrome. The incidence of late potential in signal-averaged ECG is higher in patients with Brugada syndrome (60%) than in those with early repolarization syndrome (7%) . The QT interval is relatively short in patients with early repolarization syndrome [6,23]. The QT interval is unusually short in patients with Brugada syndrome Kinetic complexity are affected by specific genetic defects (mutations in calcium channel genes), as described below . The early repolarization pattern is frequently found and is associated with an increased risk of arrhythmia events in patients with short QT syndrome .