Paced QRS fragmentation is associated with spontaneous ventricular fibrillation in patients with Brugada syndrome

Background Conduction abnormalities are involved in the pathogenesis of ventricular fibrillation (VF) in patients with Brugada syndrome (BrS). Objective We investigated whether right ventricular apical pacing (RVAP) could enhance the conduction abnormality and predict the susceptibility to VF in patients with BrS. Methods Twenty patients with BrS (n = 15) or early repolarization syndrome (ERS) (n = 5) having an implantable cardioverter-defibrillator and 11 patients with complete atrioventricular block having a pacemaker were studied. Results In BrS, 7 patients had a history of spontaneous VF [VF(+) group] and the remaining 8 did not [VF(–) group]. The number of spikes in fragmented QRS was counted during sinus rhythm and RVAP at rates of 80 and 110 beats/min, respectively. Patients with complete atrioventricular block had no spikes during RVAP. During sinus rhythm, no significant difference was observed in QRS spike numbers among VF(+), VF(–), and ERS groups. During RVAP at 110 beats/min, the sum of spike numbers in leads V1 and V2 increased and the duration of QRS fragmentation increased in the VF(+) group as compared with VF(–) and ERS groups [VF(+): 10.7 ± 3.7, 2.4 ± 3.2, and 2.4 ± 1.8 ms; P < .001; VF(−): 173 ± 32, 45 ± 44, and 49 ± 45 ms; P < .001]. According to the receiver operating characteristic analysis, the cutoff value of the sum of spike numbers in leads V1 and V2 to best discriminate between VF(+) and VF(–) groups was 4 in patients with BrS. Conclusion RVAP manifested QRS fragmented spikes, which could be associated with spontaneous VF in patients with BrS.