New Risk Stratification Markers in Brugada Syndrome

Abstract

Although spontaneous type 1 ECG has been reported as a predictor of the Brugada syndrome, many patients without documented ventricular fibrillation (VF) have this ECG type and detailed risk stratification will be required. Recently, we proposed new two ECG markers to predict patients’ risk: fragmented QRS (fQRS) and spontaneous ECG alterations (ECG-alt). The fQRS is defined as multiple spikes within QRS complex in leads V1–V3 (≥4 spikes in one lead). The ECG-alt is defined as day-by-day spontaneous ECG type change or changes in ST level ≥0.2 mV. Both fQRS and ECG-alt were frequent in patients with VF, but less frequent in patients without any symptoms (fQRS: asymptomatic patients 34%, VF patients 95%, p<0.01; ECG-alt: asymptomatic patient 44%, patients with VF 97%, p<0.01). Multivariate analysis showed both fQRS and ECG-alt were associated with occurrence of VF. Experimental studies using canine wedge preparation model of Brugada syndrome showed that the fQRS and the ECG-alt represented delayed conduction and unstable repolarization at right ventricular epicardium, respectively. Existence of both repolarization and depolarization abnormalities will be associated with initiation of the VF. Because new onset of VF is less frequent in asymptomatic patients with Brugada syndrome, these two markers should be verified by future prospective study. A recent prospective study in Italy (PRELUDE) that was reported in HRS2011 showed QRS fragmentation as significant and independent predictors of arrhythmic events (hazard ratio: 4.94).