Importance Transcatheter aortic valve replacement (TAVR) to treat aortic stenosis is complicated by heart block requiring permanent pacemaker implantation in at least 10% of cases. Objectives To better understand mechanisms underlying heart block complicating TAVR and improve prediction of intraprocedural and delayed heart block. Design, Setting, and Participants This cohort study was conducted at a single academic medical center in Boston, Massachusetts, from May 2021 to January 2024 among all patients undergoing TAVR, except those with preexisting pacemakers. A total of 409 consecutive patients undergoing TAVR were prospectively studied. An electrophysiologic study was performed at the beginning and end of the TAVR procedure. An electrophysiologist monitored the electrocardiogram (ECG) and His bundle recording continuously during the procedure. Patients were followed up for 1 year. Occurrence of high-grade atrioventricular (AV) block was related to ECG and electrophysiological, anatomic, and procedural variables. Data analysis was performed from March 2023 to May 2025. Exposures An electrophysiologist monitored the ECG and intracardiac electrograms continuously during the valve implant; patients with preexisting right bundle-branch block (RBBB) or periprocedural conduction abnormalities were discharged with an ECG monitor. Main Outcome and Measures The primary outcome was Mobitz type II or complete heart block. Results A total of 409 consecutive patients were enrolled, among whom median (IQR) age was 78.5 (73.1-83.5) years and 182 patients (44.5%) were female. Forty patients (9.7%) developed heart block requiring permanent pacemakers: block developed during the TAVR procedure in 15 patients and after TAVR in 25. Block was persistent in all patients developing block during the TAVR but paroxysmal in 20 of 25 patients with post-TAVR block. Block localized to the AV node during TAVR in 6 cases (all resolved) and in 3 patients (7.5%) with delayed block. In the remaining 9 patients that developed intraprocedural block and 22 patients developing postprocedural block, the block was infranodal. Preexisting RBBB was the only ECG or electrophysiological predictor for intraprocedural block, but preexisting RBBB did not predict postprocedural block. The best predictors of delayed heart block were His-ventricular interval of 80 milliseconds or longer at the end of the implant procedure, PR interval longer than 300 milliseconds, and AV Wenckebach cycle length of 500 milliseconds or longer post-TAVR. Conclusions and Relevance In this cohort study, the characteristics and mechanisms causing AV block during TAVR differed from delayed block. Both AV nodal and infranodal block contributed to heart block accompanying TAVR procedures.
Waks et al. (Wed,) studied this question.