Primary cardiac lymphoma in internal septum to left atrium with progressive heart failure in which cardiac magnetic resonance imaging led to the diagnosis: case report.

UNLABELLED: Primary cardiac lymphoma is an uncommon malignancy that usually affects the right atrium. We report a rare case of diffuse large B-cell lymphoma involving the interatrial septum and posterior wall of the left atrium in a 74-year-old woman who presented with chest pain and complete atrioventricular block accompanied by therapy-resistant heart failure. Results using conventional diagnostic tools including echocardiography and computed tomography were unclear, but there was moderate pericardial effusion. Despite standard heart failure therapy, symptoms progressed, so we performed cardiac magnetic resonance imaging (CMR) to exclude myocarditis. Unexpectedly, CMR showed a mass that was infiltrating the interatrial septum and the adjacent left ventricular wall, but the coronary artery structure was basically unaffected. Gallium-67 scintigraphy confirmed cardiac localization, and surgical biopsy established the diagnosis of diffuse large B-cell lymphoma. The clinical course was complicated by progressive heart failure and sepsis, and the patient was transferred for hematologic treatment. This case highlights the diagnostic value of CMR in detecting atypical primary cardiac lymphoma and delineating myocardial infiltration. In patients with unexplained heart failure and conduction abnormalities, CMR should be promptly considered to guide appropriate management and to improve outcomes. LEARNING OBJECTIVE: Primary cardiac lymphoma may present with atypical localization, including the interatrial septum, the posterior wall of the left atrium, and the basal left ventricular septum, which could cause progressive heart failure and atrioventricular block. We found cardiac magnetic resonance imaging to be especially helpful in this case for detecting cardiac tumors and myocardial infiltration. Early consideration of cardiac malignancy in unexplained conduction disturbance and refractory heart failure was helpful in diagnosis and management of our patient.