Very delayed sinus arrest during complete remission of diffuse large B-cell lymphoma invading right atrium

Diffuse large B-cell lymphoma (DLBCL)-associated arrhythmias may be due to cardiac involvement or may be chemotherapy-induced. There have been no reports of significant arrhythmias with normal cardiac function occurring during the complete remission of DLBCL. A 57-year-old female, who had had no history of abnormal electrocardiograms (ECGs) in annual medical checkups, was admitted to our hospital because of low-grade fever, night sweats, and weight loss. On admission, ECG revealed a variable rhythm consisting of sinus beats and occasional escape beats. Computed tomography and 18F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) revealed two masses in the right atrium (RA) and the uterus. Total hysterectomy was performed, and pathological findings were consistent with diffuse large B-cell lymphoma (DLBCL). Chemotherapy (R-CHOP) was initiated. After two chemotherapy cycles, RA tumors disappeared, and bradyarrhythmia simultaneously converted to sinus rhythm without antiarrhythmic drug therapy. Six months after completion of chemotherapy, FDG-PET/CT revealed negative uptake in the RA and the uterus. The patient attained complete remission of DLBCL, but ECG showed bradycardia because of sinus arrest. Our case suggests that DLBCL-induced arrhythmia can occur even after its remission and should be monitored.