Introduction Brugada syndrome is severe arrhythmia character
Brugada syndrome is severe arrhythmia characterized by specific ST elevations in precordial leads and sudden ventricular fibrillation (VF), and the condition may result in sudden cardiac death [1–5]. By implanting defibrillation devices, also known as implantable cardioverter-defibrillators (ICDs), sudden death by VF can be effectively avoided [6–7]; however, the indication of ICD in asymptomatic Brugada syndrome is controversial [2,4,5]. In accordance with the consensus report on Brugada syndrome, asymptomatic Brugada syndrome is defined as the presence of typical coved-type ST elevations in precordial leads in patients lacking a history of spontaneous VF [4,5]. ICD therapy guidelines  emphasize the importance of having only few risk factors, such as family history of Brugada syndrome, episodes of syncope, and VF inducibility [3,4,9–11]. However, in clinical practice, risk compund w is often challenging, mainly because of the difficulties in objectively evaluating ST elevations. In the consensus report, ST elevations were classified as types 1–3 on the basis of morphology and degree of ST elevation, but quantitative evaluation would often be difficult because these factors may change in different physiological situations. Additionally, several investigations have shown that patients with Brugada syndrome and spontaneous VF episodes exhibit ST elevations only on a specific area on the chest surface, such as readings obtained when the ECG leads were placed 1–3 ribs higher [12,13]. Therefore, systematic evaluation of ST elevation obtained in multiple leads is necessary for characterizing the ST elevation.
Conflict of interest
Acknowledgments This study was partly supported by a grant for scientific research from the Ministry of Education, Science and Culture of Japan (Grant no.: 23591061), and a grant of Project Research of Kitasato University Graduate School of Medical Sciences (Grant no.: 2101).
Introduction Right ventricular apical (RVA) pacing can result in ventricular dyssynchrony and decreased ejection fraction (EF), thereby leading to increased hospitalizations and mortality [1–4]. In contrast, pacing at the right septum and right ventricular outflow tract (RVOT) may result in more physiologic pacing . While echocardiographic studies suggest that right ventricular septal (RVS) pacing can improve short-term outcomes and left ventricular systolic performance [6–8], there is no definitive evidence that RVS pacing is superior to RVA pacing in the long term. This may be because there is no consistency in lead placement among studies. Most studies are potentially flawed in that the leads were positioned in the RVOT and not necessarily in the septal position [6,7–11]. Furthermore, many short-term studies have reported a physiologic benefit of RVS pacing, and the negative remodeling effect of RVA pacing can take a year or more to manifest in patients with previously normal or near-normal ventricles. Some studies have investigated the long-term effect of RVS pacing, but the duration of follow-up was limited to 18 months, and the patient population included patients with atrial fibrillation or patients with ventricular pacing. Another reason for the reluctance to accept RVS pacing among physicians may be their concerns regarding long-term lead performance (e.g., R-wave sensing, stimulation threshold, and impedance) and complications. Thus, the goal of this study is to compare the long-term effectiveness of RVS pacing vs. RVA pacing in patients with atrioventricular block.
Discussion Previous reports have suggested that prolongation of the QRS interval results in decreased LVEF and a higher risk of CHF [15,16]. Thus, there has been increasing interest in RV pacing sites that are associated with more favorable physiologic function. Some studies suggest that pacing from a septal stimulation site may produce such favorable physiologic atrioventricular conduction [6,7]. However, the absence of definitive data showing the superiority of RVS-pacing over RVA-pacing has limited the adoption of this strategy.