Abstract Body (Do not enter title and authors here): Background:
Persistent left superior vena cava (PLSVC) is a rare congenital venous anomaly that can complicate the anatomy of the right atrium and coronary sinus, posing technical challenges during catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT). Optimal ablation strategies in this subset remain poorly defined.

Methods:
We retrospectively analysed 11 patients with PLSVC who underwent typical AVNRT ablation at our centre between 2015 and 2024, identified from a cohort of 2,030 ablations (0.54%). PLSVC was suspected by dilated coronary sinus on transthoracic echocardiogram and confirmed by coronary sinus catheter manipulation or coronary sinus venography. All procedures were performed using the Claris EP Workmate system with right femoral vein access. Due to unstable His catheter positioning from distorted anatomy, fluoroscopic landmarks in the left anterior oblique (LAO 30°) view were used in review screen during radiofrequency ablation. Radiofrequency ablation (RFA) was delivered using a 4-mm non-irrigated Blazer™ catheter (max 40W, 60°C) targeting the slow pathway, guided either by low-amplitude electrograms or anatomical landmarks—primarily the anterior lip of the mid coronary sinus ostium (CSOS). A long sheath (SR0) was used in 5 patients for better catheter stability.

Results:
The mean age was 38 ± 11 years; 8 were female. Typical AVNRT was inducible in all 11 patients. Immediate procedural success was achieved in 100%, defined by non-inducibility of AVNRT post-ablation with and without isoproterenol. Junctional ectopy during energy delivery was used as a surrogate marker when slow pathway potentials were absent (8/11 patients). Long-term success at 24-month follow-up was 91%, with one recurrence. There were no major complications. In 3 patients, the slow pathway was localized to the posteroinferior septum; in the remainder, ablation was successful within the coronary sinus ostium.

Conclusion:
In patients with PLSVC, right-sided ablation of typical AVNRT remains effective, despite anatomical distortion. Atypical anterior ablation targets mostly within the Coronary sinus ostium, fluoroscopic guidance, and long sheath support facilitate successful outcomes. Awareness of these adaptations may reduce recurrence and procedural risk in this challenging subset.