Fluoroless Ablation of a Coronary Sinus-related Accessory Pathway Without Coronary Sinus Angiogram in a Patient with Multiple Prior Failed Ablations.

Accessory pathways (APs) associated with the coronary sinus (CS), often linked to diverticula, are rare and challenging to ablate, frequently requiring CS venography for anatomical guidance. We report the case of a 56-year-old woman with recurrent palpitations, manifest pre-excitation, and two prior failed ablations for a presumed posteroseptal pathway. The electrocardiogram showed an immediately negative QRS complex in the inferior leads, suggesting an epicardial CS-related pathway. Using solely three-dimensional (3D) electroanatomic mapping (CARTO™; J&J MedTech, New Brunswick, NJ, USA) without fluoroscopy or CS angiogram, we reconstructed the geometry of the right atrium, venae cavae, and CS. Mapping revealed early ventricular activation and fused atrioventricular signals in distal CS, enabling successful radiofrequency ablation at 30 W with immediate loss of antegrade conduction. No retrograde conduction persisted post-adenosine, and tachycardia was non-inducible. The patient remained symptom-free at 1-year follow-up. To the best of our knowledge, this is the first reported successful fluoroless ablation of a CS-related epicardial AP without venography, highlighting the role of advanced 3D mapping in reducing radiation and contrast risks in complex cases.