Newly induced atrioventricular nodal reentrant tachycardia after catheter ablation for atrial fibrillation: association with proximal coronary sinus ablation

Background Atrioventricular nodal reentrant tachycardia (AVNRT) is not solely caused by dual atrioventricular (AV) nodal physiology; degeneration of the atrial myocardium surrounding the AV node may also contribute to its pathogenesis. Objectives This study aimed to investigate whether ablation in regions surrounding the AV node is associated with the development of AVNRT substrate. Methods This retrospective study analyzed AF ablation procedures performed at our University Hospital from 2012 to 2024. To evaluate AF inducibility, atrial burst stimulation was repeatedly delivered from two different sites at cycle lengths ranging from 300 msec to 180 msec with 20ms decrements both at baseline and under isoproterenol administration. The incidence of AVNRT newly induced after AF ablation was investigated. Furthermore, we compared the baseline and procedural characteristics including prior specific ablation sites between patients with newly induced AVNRT (defined as the AVNRT group) and those without AVNRT (defined as the control group) and identified the factors associated with AVNRT inducibility. Results A total of 2,771 procedures (median age: 63 years; 536 women) were performed, including 2,113 first-time, 479 second-time, and 119 third or subsequent ablations. AVNRT was induced in 44 patients (1.6%) during atrial overdrive pacing for AF induction. The incidence of induced AVNRT increased with the number of ablation procedures: 1.1% during first-time ablations, 3.1% during second-time ablations, and 4.2% during third or subsequent ablations. Ablation lesions involving the coronary sinus and interatrial septum were significantly more frequent in the AVNRT group than in the control (coronary sinus: 20.5% vs 3.1%, p < 0.001; interatrial septum: 18.2% vs 4.6%, p < 0.001, respectively). In multivariate analysis, repeat AF ablation and prior ablation within CS were independent factors associated with the AVNRT provocation (adjusted odds ratio, 2.06; 95% CI, 1.03–4.01; P = 0.036 and adjusted odds ratio, 4.72; 95% CI, 1.86–11.01; P < 0.001, respectively) (Figure 1). The proportions of applications in the inferoseptal, inferior, and inferolateral CS were 33.3%, 22.2%, and 44.4% in the AVNRT group, compared with 4.9%, 19.5%, and 75.6% in the control group (Figure 2A). The distance between the CS ostium and the most proximal application point within the CS was shorter in patients with induced AVNRT than in those without (median [IQR]: 13.0 [9.2–27.5] mm vs 18.6 [20.8–34.6] mm, p = 0.056) (Figure 2B). Conclusion Ablation within the proximal CS during AF procedures may modify the atrial myocardium surrounding the AV node and create the arrhythmogenic substrate for AVNRT.