Atrial fibrillation triggered by pulmonary vein involvement in recurrent lymphoma: successful treatment with pulsed field ablation-a case report.

Background: Atrial fibrillation (AF) is associated with structural and electrical remodelling of the left atrium, but in rare cases, it may occur secondary to external compression or local inflammation. Cardiac involvement of malignant lymphoma is uncommon, and its contribution to AF mechanisms remains poorly understood. We report a case of recurrent lymphoma involving the right inferior pulmonary vein (RIPV), in which pulsed field ablation (PFA) restored sinus rhythm, supported by multimodality imaging and cytological evaluation. Case summary: A 71-year-old man with a history of follicular lymphoma presented with new-onset AF and palpitations. Contrast-enhanced cardiac computed tomography (CT) revealed an irregular soft tissue lesion involving the RIPV. A retrospective review of a prior non-contrast CT showed subtle thickening in the same region. Pulsed field ablation achieved isolation of all pulmonary veins. Although no abnormal voltage or electrograms were noted near the RIPV, AF terminated immediately upon its electrical isolation. Cytologic analysis of left atrial aspirate obtained near the RIPV revealed Class III atypical lymphoid cells. Post-ablation Positron emission tomography-CT demonstrated intense ^18F-fluorodeoxyglucose (FDG) uptake in the RIPV lesion, supporting metabolically active lymphoma. The patient remained arrhythmia-free without antiarrhythmic therapy at 1-month follow-up and was referred for haematologic treatment. Discussion: This case illustrates a rare presentation of AF associated with recurrent lymphoma involving the RIPV. Although AF termination after RIPV isolation suggests a pulmonary vein-mediated mechanism, local tumour involvement may have facilitated AF initiation from the RIPV by increasing its arrhythmogenic potential. Multimodal imaging and intracardiac cytology enabled diagnosis without biopsy, while PFA provided safe and effective rhythm control in a structurally compromised region.