The Brugada Syndrome: Can We Predict the Risk?

Abstract

The Brugada syndrome (BS) is now recognized as an important condition predisposing individuals with a seemingly normal heart to sudden death due to ventricular fibrillation (VF).1 Mutations in the gene encoding the cardiac sodium channel (SCN5A) have been found in 18–30% of patients with BS.2 It is believed that abnormalities in regional repolarization and/or depolarization provide the electrophysiological milieu for VF.3,4 In a recent consensus statement,5 the electrocardiographic features have been categorized as follows: type 1 (diagnostic for BS): coved ST segment elevation of ≥2 mm followed by a negative T wave in more than one of leads V1–3; type 2 (not diagnostic for BS) saddleback shaped ST segment elevation with ST elevation of ≥2 mm and a trough ≥1 mm ST elevation; or type 3 (not diagnostic for BS) coved or Saddleback ST segment elevation of <1 mm. However, type 2 and 3 pattern are considered diagnostic, if the ST segment elevation converts to a type 1 pattern after administration of a cardiac sodium channel blocking drug. Data from the largest patient series6 have shown that the highest risk for clinical events (sudden death, syncope) occurs in those patients who have a prior aborted sudden death (62% at 54 ± 54 months follow-up), followed by those with syncope and spontaneously abnormal, type 1 pattern ECG (19% at 26 ± 36 months follow-up). However, the event rate among asymptomatic patients was still 8% (27 ± 29 months follow-up). Data from this series suggest that among these asymptomatic patients, the risk is highest in those with spontaneously diagnostic type 1 ECG pattern and lower if they develop this ECG pattern only after administration of a sodium channel blocking drug. The risk was also high in those with inducible VT/VF at electrophysiologic study. Other studies, however, report a much lower event risk in asymptomatic patients and found that VT/VF inducibility was not predictive of future events.7 This difference may in part relate to patient selection including only patients with type 1 pattern ECG versus including also those with type 2 and 3 ECG pattern as well as the electrophysiologic stimulation protocol used.8 Thus, risk stratification in asymptomatic individuals with the Brugada ECG is still a challenge. The diagnostic classification as well as risk stratification based on the three ECG patterns may be questionable since the ECG may spontaneously change from one pattern to another in the same individual.9