Progression of electrocardiographic abnormalities associated with initial ventricular fibrillation in asymptomatic patients with Brugada syndrome.

BACKGROUND: Various risk stratifications in asymptomatic patients with Brugada syndrome (BrS) have been proposed, but the electrophysiological change that promotes ventricular fibrillation (VF) is still unknown.

OBJECTIVE: The aim of this study was to clarify the changes in electrocardiographic (ECG) markers at the onset of VF from ECGs recorded when patients were still asymptomatic.

METHODS: The subjects of this study included 14 patients with VF and 48 consecutive asymptomatic patients with BrS. We compared ECGs before the initial VF events (>6 months; early phase) with ECGs at the initial VF events (late phase). In asymptomatic patients, we evaluated ECGs at 2 time points with an interval of >6 months. We evaluated various ECG markers including type 1 ECG and fragmented QRS (fQRS; multiple spikes within the QRS complex).

RESULTS: ECG parameters of the early and late phases were not different except for decreased ST voltage and low incidence of type 1 ECG in asymptomatic patients. There were no differences in ECG parameters of the early phase between patients with VF and asymptomatic patients. In patients with VF, ECGs at the late phase had longer QRS intervals and intervals between the peak and the end of the T wave and more frequent type 1 ECG and fQRS than did ECGs at the early phase. Those changes were associated with initial VF events (QRS widening: odds ratio [OR] 11.5, P < .01; interval between the peak and the end of the T wave: OR 11.6, P < .01; fQRS: odds ratio 15.3, P < .01; type 1 ECG: OR 6.6, P < .05).

CONCLUSION: QRS and ST-T wave abnormalities developed in association with the initial VF events. Aggravation of the conduction disturbance in addition to BrS-ECG promotes VF.