In patients with syncope episodes detecting type ECG
In patients with syncope episodes, detecting type 1 ECG (spontaneous or drug-induced) and evaluating the characteristics of symptoms are important for determining the indication for ICD implantation. The result of EPS is supportive; however, it should be noted that VF is not induced during EPS in all patients who have spontaneous VF episodes and that syncope is an important symptom preceding VF. The existence of fQRS, ER, and exercise-induced ST augmentation should also be considered (Table 3).
Conflict of interest
Acknowledgments This work was supported by a Grant-in-Aid for Scientific Research (C, 50322227) of Japan Society for the Promotion of Science (JSPS) and a research grant for cardiovascular diseases (H24-033) from the Ministry of Health, Labor, and Welfare of Japan.
Introduction Brugada syndrome is a condition associated with right bundle-branch block, ST elevation in the right precordial leads, [1–5] and ventricular fibrillation (VF) in patients without any apparent molarity calculation disease, [1–5] it is relatively frequent in Japan [6,7] and Asia . Although the abnormalities of the so-called Brugada-type (type 1 or coved type) electrocardiograph (ECG) are the most useful parameters for the diagnosis of Brugada syndrome, the ST elevation is not constant in some patients with this syndrome and presents as an intermittent or concealed Brugada syndrome . Therefore, the exact event rate is unclear. The incidence of sudden cardiac death is considered to be the highest at least in patients with documented VF. Placement of implantable cardioverter–defibrillators (ICDs) is known to be the only and most powerful treatment modality for the prevention of sudden cardiac death in patients with a history of VF and/or aborted sudden cardiac death, i.e., for the so-called secondary prevention of sudden cardiac death . The recurrence rate of VF in patients with Brugada syndrome is significantly higher, at 10% per year,  than other types of idiopathic VF [6,10]. On the other hand, the incidence of de novo VF occurring in patients with asymptomatic Brugada syndrome is very low [10–13]. However, the cardiac events caused by this disease are very harmful and lethal. In the light of the final cardiac event in asymptomatic patients with Brugada syndrome, it appears that these patients appear to have a poor prognosis . However, ICDs can be used to completely prevent sudden cardiac death in such patients. Therefore, it is important to define the criteria for identifying high-risk patients among those without severe Brugada-type ECG changes.
General aspects of the prognosis in patients with Brugada syndrome The prognosis of patients with a Brugada-type ECG naturally depends on the clinical types, on the basis of which the patients can be classified into the following groups: those with documented VF (symptomatic group), a syncope group, and an asymptomatic group. It is very difficult to accurately determine the distribution of these three groups among patients with the Brugada syndrome in the general setting, and according to major studies, it varies from 6.0–21.2% in the symptomatic group [11,15], 18.8–30.7% in the syncope group, [11,16] and 56.9–63.6% in the asymptomatic group [4,15] (Table 1) [4,11,15,16]. The annual cardiac event rate also varies and is 5.0–11.5% in the symptomatic group [4,16], 0.6–5.4% in the syncope group [4,11] and 0.24–3.6% in the asymptomatic group [4,16] (Table 1). A multicenter study on patients with Brugada syndrome  included 220 patients (46±12 years) with the type 1 Brugada ECG pattern who underwent ICD placement at14 centers, between 1993 and 2005. During a mean follow-up period of 38±27 months after the ICD implantation, no deaths occurred. Eight patients (3.6%) form this population experienced appropriate shocks. The three groups defined according to the ICD indications differed significantly in the rate of appropriate shocks (aborted sudden cardiac death, 22%; syncope, 10%; asymptomatic, 4%; p<0.025) during the follow-up. During the time to the first appropriate shock depending on the symptoms, two patients had shocks for monomorphic ventricular tachycardia (VT) (cycle length, 350 and 280 ms), and 16 had shocks for polymorphic VT or VF (mean cycle length, 199±37ms [range 160–260ms]). Patients with appropriate therapy had 10±15 shocks occurring 26±33 months after the ICD implantation. Seven patients (3.2%) presented with an arrhythmic storm and were treated with quinidine or ablation (4 patients) in the event of quinidine failure .