Incidence of conversion to sinus rhythm in refractory atrial fibrillation patients after atrioventricular node ablation with conduction system pacing
Authors: Ivanovski M , Mrak M , Zupan Meznar A , Antolic B , Klemen L , Stublar J , Jan M , Pernat A , Zizek D 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
"Ablate and pace" strategy is a reasonable therapeutic option in refractory atrial fibrillation (AF) when rhythm or rate control cannot be achieved with catheter ablation or pharmacological therapy. Atrioventricular node ablation (AVNA) combined with conduction system pacing (CSP), including His-bundle pacing (HBP) and left bundle branch pacing (LBBP), are increasingly adopted, as they offer more physiological activation of the left ventricle compared to other pacing modalities. However, the incidence of conversion to sinus rhythm after "ablate and pace" strategy with CSP is not known.

Purpose
To determine the incidence of spontaneous conversion to sinus rhythm and its predicting factors in patients undergoing AVNA and CSP.

Methods
Refractory AF patients undergoing AVNA with CSP at our institution between June 2018 and May 2022 were prospectively included. Echocardiographic and clinical parameters including ECG were assessed at baseline and 6 months after the procedure.

Results
Sixty-three patients (male 41.3%, age 71±9 years, left ventricle ejection fraction (LVEF) 40% (IQR 20)) were included. Thirty-seven patients (58.7%) received HBP and 26 patients (41.3%) LBBP. During follow-up, spontaneous conversion to sinus rhythm (SR) was registered in 5 patients (8%); 3 in HBP group and 2 in LBBP group. Baseline characteristics of patients who converted to SR did not differ from non-sinus rhythm (NSR) patients except for left atrial volume index (LAVI), which was smaller in SR group (43 mL/m2 (IQR 6) vs. 60 mL/m2 (IQR 19); p&lt;0.01). Multiple regression model confirmed an inverse association between LAVI and conversion to sinus rhythm even after considering other clinically relevant covariates (odds ratio=0.685, p=0.03). At follow-up, LAVI did not change in any group (SR: p=0.345; NSR: p=0.508). LVEF increased in both groups, from 40% (IQR 20) to 51% (IQR 18) in NSR group (p&lt;0.01) and from 41% (IQR 11) to 54% (IQR 11) in SR group (p=0.138), although the increase in SR group did not reach statistical significance due to small sample size. Similarly, ESVi decreased in both groups; in NSR group (from 47 mL/m2 (IQR 33) to 29 mL/m2 (IQR 24), p&lt;0.01) and in SR group (from 33 mL/m2 (IQR 19) to 25 mL/m2 (IQR 0), p=0.176), where statistical significance was not reached due to small sample size and small initial volumes. Symptomatic improvement according to NYHA class was more pronounced in SR group (p=0.026).

Conclusion
The results of our study show that spontaneous conversion to sinus rhythm after AVNA combined with CSP is not uncommon, especially in patients with smaller left atria. Patients who converted to SR showed superior symptomatic improvement compared to NSR patients. Larger studies are warranted to clarify the predicting variables of SR restoration in these patients, which should be considered for initial atrial pacing lead implantation (dual-chamber device) when "ablate and pace" strategy is adopted.