A new study has revealed that high-grade atrioventricular (AV) blocks occurring during transcatheter aortic valve replacement (TAVR) have different mechanisms and predictors compared to those that develop after the procedure. The findings suggest that distinct risk stratification models are necessary to identify patients at risk for this common complication.¹

This prospective cohort study enrolled 409 consecutive patients (median age 78.5 years; 44.5% female) undergoing TAVR at a single academic medical centre in Boston, MA, US. Patients with pre-existing pacemakers were excluded. An electrophysiologist continuously monitored the electrocardiogram (ECG) and His bundle electrograms during the valve implantation, with electrophysiologic studies performed at the beginning and end of the procedure. The primary outcome was the development of Mobitz type II or complete heart block, with patients followed for up to 1 year.¹

Overall, 9.7% of patients (40/409) developed a high-grade AV block that required permanent pacemaker implantation. The timing and nature of these blocks varied significantly.

Intraprocedural blocks occurred in 15 patients and were persistent in all cases. The only significant predictor for these events was a pre-existing right bundle-branch block (RBBB).

In contrast, delayed blocks developed in 25 patients after the TAVR procedure and were mostly paroxysmal (80%). Predictors for delayed block included a post-TAVR His-ventricular interval of ≥80 ms, a PR interval >300 ms, and an AV Wenckebach cycle length of ≥500 ms.

Patients who developed blocks during TAVR had a much higher ventricular pacing burden at 1 month (median 97.4%) and 1 year (93.5%) compared to those with delayed blocks (5.8% and 9.2%, respectively).¹

The study highlights that the timing of heart block in relation to the TAVR procedure is associated with different underlying mechanisms, predictors, and clinical characteristics. "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," stated lead author Dr Jonathan Waks and colleagues.¹

In an accompanying editorial, experts noted that the findings support "consideration of a more selective, physiology-guided strategy, which may include shorter observation for transient block, targeted monitoring for newly prolonged conduction intervals, and potential reduction in unnecessary pacemaker implantation."²

References

1. Waks JW, Poulin M, Clarke JD, et al. Mechanisms Underlying Alterations in Cardiac Conduction After Transcatheter Aortic Valve Replacement. JAMA Cardiol. Published online December 10, 2025. https://doi.org/10.1001/jamacardio.2025.4442

2. Patton KK, Windecker S. Mechanistic Insights Into Post-TAVR Atrioventricular Block. JAMA Cardiol. Published online December 10, 2025. https://doi.org/10.1001/jamacardio.2025.4447

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