Ct-derived basal septal thickness predicts Post-TAVR pacemaker implantation in patients with preexisting right bundle branch block.

Background: Conduction disturbances requiring permanent pacemaker implantation (PPI) remain common after transcatheter aortic valve replacement (TAVR). This study evaluated whether pre-procedural CT-derived basal muscular interventricular septal (IVS) thickness predicts PPI within 1 month post-TAVR in patients with preexisting right bundle branch block (RBBB). Methods: In 66 TAVR patients with severe aortic stenosis and preexisting RBBB, IVS thickness was measured at 2, 4, 6 and 8 mm below the membranous septum (MS) on CT coronal views. Univariate /multivariate logistic regression were used to identify predictors, and receiver operating characteristic (ROC) analysis evaluated predictive performance. Results: PPI was required in 28 patients (42.4%). The PPI group exhibited significantly thinner IVS across all measured levels (all P < 0.05). Univariate analysis revealed that every 1-mm increase in IVS thickness at 2 mm below MS, the risk of PPI was markedly reduced (OR 0.003, 95% CI: 0.001-0.059). Multivariate analysis adjusting for age, implantation depth, and membranous septum length (MSL) confirmed that IVS thickness < 4.35 mm at 2 mm below MS (adjusted OR 0.05, 95% CI: 0.01-0.32, P = 0.002) and lower MSL-implantation depth difference (MSL-ID) were independent predictors of PPI. The model incorporating IVS thickness showed excellent discrimination (AUC 0.91, 95% CI: 0.84-0.98), superior to the model without it (AUC 0.82, 95% CI: 0.71-0.92). Conclusions: Pre-procedural CT-derived basal IVS thickness independently predicts post-TAVR PPI in patients with preexisting RBBB. Thinner IVS may reflect less anatomical protection for the conduction system during valve deployment. Integrating IVS thickness into risk assessment could improve patient stratification and procedural planning.