Several mechanisms are responsible for heart block complications during and after transcatheter aortic valve replacement (TAVR) for the treatment of aortic stenosis (AS), a new cohort study shows. Mechanisms differed between periprocedural heart block and post-TAVR or delayed heart block. Jonathan W. Waks, MD, of the Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, and colleagues, reported these results in a manuscript published Wednesday online in JAMA Cardiology. At least 10% of patients who receive TAVR for AS end up needing a permanent pacemaker due to heart block. The mechanisms behind heart block may differ between patients depending on the type of heart block. The investigators in this single-center cohort study, which took place from May 2021 through January 2024, examined the mechanisms behind heart block as a complication of TAVR. Follow-up occurred 1 year after TAVR. Data were analyzed between March 2023 and May 2025. A total of 409 patients (median age=78.5 years, 44.5% female; 95.4% White) were studied prospectively, and an electrophysiologic study was performed before and after the TAVR procedure. The patients had electrocardiogram (ECG) recordings monitored while undergoing TAVR. Patients who had prior right bundle brand block (RBBB) or conduction abnormalities during the procedure were given an ECG monitor upon leaving the hospital. Permanent pacemakers were required in 40 (9.7%) of TAVR patients, 15 of which developed heart block during the procedure and 25 of which developed heart block after TAVR. Block was paroxysmal in 20 of the 25 patients with post-TAVR block. Heart block localized to the atrioventricular (AV) node in six patients, and all were resolved, while three patients had delayed block. Heart block was infranodal in the rest of the patients (nine who had intraprocedural block and 22 patients with postprocedural block). Intraprocedural block was only predictable by ECG through preexisting RBBB. Postprocedural block was not predictable with preexisting RBBB. Delayed heart block was best predicted by His-ventricular interval longer than 80 milliseconds after TAVR, PR interval longer than 300 milliseconds or AV Wenckebach cycle length that was longer than 500 milliseconds after TAVR. Overall, several factors influence the development of heart block in patients with AS undergoing TAVR. Some factors include anatomic, procedural and electrocardiographic measures. In an accompanying editorial, Kristen K. Patton, MD, from the University of Washington, Seattle, and Stephan Windecker, MD, from the University of Bern, Switzerland, wrote about conduction disturbances during TAVR and the complications of heart block. “Waks et al. provide evidence to refine current guidance and move the field toward a more personalized, physiology-guided approach to post-TAVR conduction disturbances,” the editorialists concluded. Sources: Waks JW, Poulin MF, Clarke JRD, et al. Mechanisms underlying alterations in cardiac conduction after transcatheter aortic valve replacement. JAMA Cardiol. 2025 Dec 10 (Article in Press). Patton KK, Windecker S. Mechanistic insights into post-TAVR antrioventricular block. JAMA Cardiol. 2025 Dec 10 (Article in Press). Image Credit: Koragot kaewmahakhun – stock.adobe.com