Is the anatomical relationship between the membranous septum and transcatheter valve truly associated with conduction disturbances after TAVR? a postprocedural CT-based analysis

Background Previous studies have suggested the relative relationship between membranous septum (MS) length and device implantation depth is associated with conduction disturbances following transcatheter aortic valve replacement (TAVR). However, no study has evaluated the actual anatomical relationship between the implanted transcatheter valve and the MS using postprocedural imaging modalities, nor its association with new conduction disturbances. Purpose The aim of this study was to determine whether the transcatheter valve position relative to the MS assessed by postprocedural contrast-enhanced cardiac computed tomography (CCT) is associated with the incidence of conduction disturbances. Methods This single-center retrospective observational study included consecutive patients who underwent TAVR at our institution and had postprocedural CCT available between March 2018 and December 2024. A total of 235 patients were analyzed (age 83 ± 5 years; 156 women ［66%］; self-expanding valves in 145 patients ［62%］). The transcatheter valve position relative to the MS was evaluated at the commissural plane between the non-coronary and right-coronary cusps. Patients were classified into the Within-MS group which is the transcatheter valve edge located within the MS region, and the Outside-MS group which is the transcatheter valve position below the MS as shown in Figure. The primary outcome measure was the incidence of new permanent pacemaker implantation (PPI) within 1 month following TAVR. Results Valves were positioned within the MS in 167 patients (71%), including 70 balloon-expandable valves (78%) and 97 self-expanding valves (67%) cases. New-onset complete left bundle branch block (LBBB) immediately after TAVR occurred in 87 patients (37.0%). The incidence decreased to 29 patients (12.3%) at 48 hours and only 14 patients (6.0%) had persistent complete LBBB at 1 month. There were no significant differences between the Within-MS (n=167) and the Outside-MS (n=68) groups at any time point. New PPI within 1 month was required in 4 patients (2.4%) in the Within-MS, whereas it was in 7 patients (10.3%) in the Outside-MS groups (P=0.03). Conclusion(s) The current study firstly confirmed that implantation of the transcatheter valve beyond the MS was associated with a significantly higher incidence of new PPI using postprocedural CCT, further supporting the practice of preprocedural assessment of MS length and individualized planning of valve implantation depth for minimizing conduction complications.