Characterisation of patients with late pacemaker implantation after ablation for AVNRT or septal accessory pathways

Background and Aim

The risk for permanent atrioventricular (AV) block and subsequent pacemaker (PM) implantation after ablation for atrioventricular nodal reentry tachycardia (AVNRT) or atrioventricular reentry tachycardia (AVRT) caused by septal accessory pathways (AP) is increased. This work aims to characterise these patients included in local ablation and PM registries at a tertiary health care centre in Austria.

Methods

Data from patients from the local ablation registry who underwent ablation of AVNRT or AVRT between 2015 and 2024, were included in the analysis. Data regarding PM implantations were taken from the local PM implantation registry. Patients, which already had a PM implanted at the time of ablation were excluded. Data of the two registries were merged using the unique social security number as identifier. Patients with PM implantation were only included, if AV block was the indication for PM implantation. Late PM implantation (LPMI) was defined as PM implantation ≥ 30 days post ablation. Patients were characterised by age at time of ablation, sex, number of ablations delivered, and application of a 3D electroanatomical mapping (EAM) system.

Results

Between 2015 and 2024, 868 patients underwent ablation for AVNRT (57.7 % female), and 295 patients underwent ablation for AVRT (33.1 % female). Median follow up in the AVNRT group was 5.3 years (IQR 2.5-7.7), and 5.6 years (IQR 2.5-7.7) in the AVRT cohort, respectively.

Of the AVNRT patients, 8 (1.0 %) of 868 underwent PM implantation within the first days after ablation, and 2 (0.2 %) after ≥ 30 days (679 and 1217 days). Four (1.4 %) of the 295 AVRT patients needed PM implantation — 3 within the first 8 days, 1 at day 52. Importantly, the single patient with LPMI developed AV block already at the time of AVRT ablation, but because of an adequate escape rhythm and to allow the possibility for recovery, PM implantation was delayed.

EAM was used in 1.76 % of AVNRT patients (not in the 2 patients with LPMI), and in 51.76 % of AVRT patients, including the one with LPMI.

Except for 7 patients of the AVRT group, who were ablated using cryo catheters (CC), RF was the energy form of all the AVNRT and AVRT ablations. CC were used only in patients with a septal AP close to the conduction system. None of the CC patients suffered from AV block and subsequent PM implantation. In the AVNRT group a median of 5 (IQR 3-9), and in the AVRT group a median of 4 (IQR 2-10) ablations were performed.

Conclusion

While EAM and CC are commonly employed for ablation in challenging anatomical AP locations, AV block remains a potential complication during procedures targeting AVRT or AVNRT. In our local registry, all cases of AV block in patients undergoing ablation for an AP occurred during the procedure itself. Additionally, 0.2 % of individuals who underwent ablation for AVNRT experienced delayed onset AV blocks necessitating pacemaker implantation.