Abstract 4367976: Aortic Tortuosity Predicts Conduction Disturbances After TAVR via Aortic Angle and Membranous Septum Length: A Structural Equation Modeling Approach

Background: Transcatheter aortic valve replacement (TAVR) has broadened treatment options for elderly patients with severe aortic valve stenosis (AVS), including those with challenging vascular anatomy such as increased aortic tortuosity. We previously demonstrated that a higher aortic tortuosity index (ATI), defined as the ratio of aortic length (from the sinotubular junction to the terminal aorta) to body height measured by 3D-computed tomography, was associated with complete atrioventricular block (CAVB). However, the anatomical mechanisms linking ATI to conduction disturbances (CD) requiring pacemaker implantation (PMI) remain unclear. Purpose: To investigate whether anatomical variations—specifically, aortic angle and membranous septum (MS) length—mediate the association between ATI and CD requiring PMI after TAVR. Methods: We analyzed 198 consecutive patients with severe AVS who underwent TAVR. ATI, aortic angle, and MS length were quantified using pre-procedural 3D-CT imaging. CD requiring PMI within 30 days post-TAVR was observed in 20 patients (10.2%). Patients were stratified by median ATI (3.24), aortic angle (49°), and MS length (3.3 mm). Structural equation modeling (SEM) was applied to evaluate both direct and indirect effects of ATI on CD through aortic angle and MS length. Results: Patients with higher ATI (>3.24) had a significantly greater incidence of CD requiring PMI than those with lower ATI (18.2% vs. 3.0%, p = 0.001). SEM demonstrated a significant direct effect of higher ATI on CD (path coefficient = 0.26, p < 0.01), along with a significant indirect effect mediated by aortic angle and MS length (path coefficient = 0.15, p < 0.05). Conclusion: Higher ATI is associated with increased risk of CD requiring PMI after TAVR, and this relationship is mediated by steeper aortic angle and shorter MS length. Aortic tortuosity may reflect age-related anatomical remodeling that predisposes patients to conduction injury during TAVR.