Response to Avi Shimony and Guy Amit: Right ventricular outflow tract pacing: the suitable technology, the accurate place, and the right patient

Co-First Author. We really appreciate your interest in our article published in the March 2012 issue of the Europace.1 We would like to thank you for your comments and opinions on right ventricular outflow tract (RVOT) pacing.2 The right ventricular apex (RVA) has been the elective pacing site in patients with potentially life-threatening bradycardias since 1959, because it is easily accessible, readily identified, and associated with a stable position and reliable chronic pacing parameters. Nevertheless, the conventional RVA pacing may have detrimental effects on atrial fibrillation, cardiac structure, and left ventricular (LV) function, which are associated with the development of heart failure.3 These harmful effects led to an interest in alternative right ventricular pacing sites aiming to achieve a more ‘physiological’ pattern of ventricular activation. Alternate site pacing may involve the His bundle and para-Hisian tissues, the mid-septum or the low septum, RVOT, and in particular, the RVOT septum. Although several recent studies have found favourable effects on alternative site pacing, the results are still controversial and unable to draw a clear conclusion. As mentioned in your letter and review,4 non-apical pacing had significant beneficial effect on LV ejection fraction (LVEF) at the end of follow-up in patients who had low LVEF at baseline as compared with RVA pacing, but not in patients in whom LVEF at baseline was ≥40–50%. Your opinion is consistent in our results that RVOT pacing in atrioventricular block patients over 1 year is superior to RVA pacing as regards regional LV performance, LV global electromechanical delay, and interventricular mechanical delay, but not on LVEF and LV volumes.1 However, we cannot reach exactly the same conclusion as yours, which might be due to the small sample size, short-term follow-up (12 months), and without comparison with patients who have low LVEF at baseline in our study. It is true that the results we obtained so far have not shown superiority for alternative site pacing in terms of important clinical endpoints such as mortality, so that large-scale multicentre clinical trials with clinical endpoints are warranted to conclusively define the usefulness of RVOT or RV septal pacing. Furthermore, the question remains as to whether these lead positions in RVOT are anatomically correct and concerns about the long-term stability and the safety of the leads, so that RVOT pacing is still not widely recommended in patients requiring permanent cardiac pacing. It has been demonstrated that lead placement and stability in the RVOT are no longer a problem with active fixation techniques and tools for placement of pacing leads onto the accurate site.5 Thus, we advocate the overwhelming majority of implanters to adopt RVOT pacing to minimize the potential of harm to their patients. Conflict of interest: none declared.