Impact of premature activation of the right ventricle with programmed stimulation in Brugada syndrome
Brugada syndrome (BrS) is associated with sudden cardiac death because of polymorphic ventricular tachycardia and/or ventricular fibrillation (PVT/VF) in patients without apparent structural heart disease. Typical coved‐type ST segment elevation in right precordial leads on electrocardiogram (type‐1 ECG) is crucial for the diagnosis of BrS and link to the development of PVT/VF.1 On the other hand, saddle‐back type ST segment elevation (type‐2 or type‐3 ECG) is not diagnostic of BrS and at a low‐risk for PVT/VF unless converted to type‐1 ECG with sodium‐channel blocker challenge or fever. Despite considerable research, it is still controversial whether repolarization or depolarization abnormalities (conduction delay) are responsible for physiological mechanism of type‐1 BrS ECG. Some reports have indicated a relationship between the development of type‐1 ECG and conduction delay in the RV.2 Tukkie et al. reported that later onset of contraction in RV than that in LV is associated with ST‐segment elevation and type‐1 ECG analyzed with echocardiography.8 Postema et al. also reported the association between type‐1 ECG and conduction slowing of RV with noninvasive electrocardiographic techniques.9 Furthermore, Nademanee et al. recorded epicardial electrograms of the RV outflow tract (RVOT) directly and found delayed and fragmented potentials.11 They reported that type‐1 ECG converted to type‐2, type‐3, or normal ECG after elimination of delayed or fragmented potential with catheter ablation. On the other hand, complete right bundle‐branch block (CRBBB), which also causes delayed activation in the RV, can mask the typical BrS ECG and sometimes make it difficult to diagnose BrS.12
We assumed that premature RV stimulation on electrophysiological study (EPS) allows artificial premature RV activation and can unmask the influence of delayed activation in the RV including CRBBB. The purpose of the present study was to investigate the impact of gradually premature activation in the RV on morphological change of ECG using single premature stimulation of the RV in BrS patients including those with concomitant CRBBB.