From Anatomy to strategy: Using Bicuspid Aortic Valve Morphology and Membranous Septal Length to Predict Conduction Disturbances After Surgical Aortic Valve Replacement

All articles of this category (opens in new window) Background: Conduction disturbances—particularly permanent pacemaker implantation (PPI) and new-onset left bundle branch block (LBBB)—remain clinically relevant after surgical aortic valve replacement (SAVR). Bicuspid aortic valve (BAV) morphology and a short membranous septum length (MSL) increase vulnerability to conduction disturbances, as shown in transcatheter aortic valve replacement cohorts. Methods: We retrospectively screened 1,243 consecutive SAVR cases between 2018 and 2024. Patients undergoing concomitant procedures (coronary artery bypass grafting or mitral/tricuspid valve surgery), as well as having tricuspid aortic valves, were excluded. A total of 136 BAV patients were included. Morphology distribution according to Sievers’ classification was: right–left (R/L) fusion n = 72, right noncoronary (R/N) fusion n = 42, left noncoronary (L/N) fusion n = 10, and type 0 n = 12. To optimize statistical comparability for outcomes, type 0 and L/N were excluded from the comparative analysis, focusing on R/N vs. R/L. Preoperative ECG-gated CT was used to measure MSL. The primary endpoint was new PPI within 30 days; the secondary endpoint was persistent LBBB at discharge. Propensity-score matching yielded 40 R/N–R/L pairs ( n = 80). Results: Across BAV subtypes (descriptive anatomy), R/N fusion had the shortest MSL (4.1 ± 1.0 mm) compared with R/L (5.3 ± 1.1 mm) and the combined type 0/L–N group (5.7 ± 1.2 mm), p < 0.001. In the matched R/N vs. R/L cohort ( n = 80), PPI occurred in 9/40 (22.5%) R/N vs. 2/40 (5.0%) R/L; odds ratio (OR) 5.52 (95% CI: 1.11–27.43), p = 0.03. LBBB was more frequent in R/L than R/N: 14/40 (35.0%) vs. 5/40 (12.5%); OR 3.77 (95% CI: 1.21–11.79), p = 0.02. In adjusted models, each 1-mm shorter MSL increased PPI odds by 44% (adjusted OR 1.44 per mm; 95% CI: 1.13–1.84; p = 0.003) and increased LBBB odds (adjusted OR 1.42 per mm; 95% CI: 1.03–1.97; p = 0.033). R/N morphology was independently associated with PPI (adjusted OR 2.96; 95% CI: 1.05–8.36; p = 0.04). Conclusion: In this BAV-only cohort, R/N fusion exhibited the shortest CT-measured membranous septum and the highest risk of pacemaker implantation, while R/L fusion more frequently developed LBBB. Membranous septum length emerged as a strong, independent predictor of PPI and LBBB. These data argue for strategy adaptation: preoperative integration of BAV fusion pattern and septal length should directly inform operative planning and prosthesis selection, especially in the context of evolving guidelines that extend TAVI to younger patients. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany