Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp diopathic ventricular fibrillation (VF) has been recognized as a cause of unexplained nocturnal sudden death in middle-aged men, especially in South-East Asian countries. In some of these patients with idiopathic VF, a high takeoff ST segment and prominent J wave in the right precordial ECG leads (Brugada type) or inferolateral leads (J-wave type) have been reported. 1,2 A prominent transient outward current (Ito) may play an important role in the genesis of the J wave. 3 Both the Brugada type and J-wave type of idiopathic VF have some similar clinical characteristics, such as VF episodes at night, male predominance, familial occurrence, triggered by high fever, suppression by isoproterenol, and exacerbation by β-blockers. Because of the similarities between the 2 types, "J-wave syndromes" was proposed by Antzelevitch and Yan. 3
Article p 624Cardiologists may be consulted about the risk of arrhythmic death after an incidental discovery of the Brugada or J-wave type ECG during a routine healthcare examination. The probabilities of induced VF by electrophysiological study (EPS) in patients with Brugada syndrome (BS) are highest for cardiac arrest survivors and lowest for asymptomatic patients. Thus, most cardiologists recommend an EPS for risk stratification of patients presenting with a Brugada-like ECG. However, the reliability of VF induction during EPS as a predictive indicator of a future spontaneous VF episode remains controversial.There is general agreement on the excellent negative predictive value of EPS but not on the positive predictive value. In the Brugada series, 34% of 263 asymptomatic patients had inducible VF and 12% of them developed spontaneous VF. 4 But in the meta-analysis by Paul et al, 25% of 720 asymptomatic patients had inducible VF and only 7% of them developed spontaneous VF, with a mean follow-up 34 months. 5 The clinical significance of VF induction in asymptomatic patients with triple extrastimuli and shorter coupling intervals is problematic. As the number of asymptomatic patients who have inducible VF increases, many cardiologists have wondered whether or not such patients should undergo implantable cardioverter defibrillator (ICD) implantation. Unfortunately we do not know how to predict the true risk of a future VF episode in asymptomatic BS patients.In this issue of the Journal, Hiratsuka et al compare the characteristics of induced VF cycle length between symptomatic and asymptomatic BS patients using fast Fourier transformation (FFT) analysis. 6 Symptomatic BS had a significantly shorter effective refractory period (ERP) at a basic cycle length (BCL) of 600 ms at the right ventricular outflow tract (RVOT) compared with asymptomatic patients. The mean VF duration induced by EPS was 14.6 s, most of them terminated electrically, and the dominant frequency (DF) of VF significantly increased with the duration of VF. Symptomatic BS patients had a higher DF of VF compared with asymptomati...