Pulsed field ablation of the coronary sinus and mitral isthmus with the lattice-tip catheter: promising acute results, uncertain durability

Background Coronary sinus (CS) isolation is often required to achieve a durable mitral isthmus (MI) block. Data regarding pulsed field ablation (PFA) of these structures are scarse. Purpose To demonstrate acute and chronic CS isolation and MI block in non-paroxysmal AF patients using the lattice-tip catheter. Methods We analysed prospectively collected data of consecutive patients undergoing PFA and subsequent remapping from November 2024 to September 2025. MI block was achieved delivering multiple lesions from the left inferior pulmonary vein to the mitral valve in a linear fashion. CS isolation was performed endocardially from the floor of the left atrium and epicardially inside the CS. During ablation at the CS ostium, a short lesion (1second) was first delivered; if no atrioventricular block(AVB) occurred, a standard lesion (4seconds) was subsequently applied. Results A total of 182 patients (107,58.8% male) were included in our analysis. Acute coronary sinus isolation was achieved endocardially in all patients with a mean of 14±4 applications. Additional 6±3 epicardial applications were delivered to ensure durability. The first 1-second application at the CS ostium induced a transient AVB in 4 patients, which resolved within 1 minute. The catheter was then advanced further into the CS, where no AVB occurred, allowing delivery of a standard lesion. Acute MI block was observed in all with 18±5 application. During remapping at 98±24 days persistent MI block and CS isolation was found in 95(52.2%) and 83(45%)patients respectively. Conclusion Despite acute CS isolation and MI block appearing feasible with PFA, chronic durability remains uncertain.