Case report: primary cardiac lymphoma presenting as acute coronary syndrome and atrioventricular block due to right coronary artery compression

Abstract Background Cardiac tumours are exceedingly rare and often present with non-specific clinical manifestations, making diagnosis challenging. Primary cardiac lymphoma represents a small proportion of primary cardiac tumours and may occasionally mimic acute coronary syndromes due to mass effect on coronary arteries or the conduction system. Case summary We report the case of a 61-year-old woman admitted for syncope who subsequently developed chest pain, inferior ST-segment elevation myocardial infarction, and complete atrioventricular block. Emergency coronary angiography revealed no obstructive coronary disease but demonstrated extrinsic compression and stiffness of the right coronary artery. Transthoracic echocardiography identified a large right ventricular mass with tricuspid valve involvement and right ventricular inflow obstruction, associated with pericardial and pleural effusion. Multimodality imaging with computed tomography and positron emission tomography showed a large hypermetabolic cardiac mass with mediastinal lymphadenopathy. Histological analysis from a computed tomography-guided biopsy confirmed primary cardiac high-grade B-cell lymphoma. Chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone was initiated, leading to significant tumour reduction but complicated by transient chemotherapy-induced left ventricular dysfunction, which was managed through a multidisciplinary cardio-oncology approach. Despite initial clinical and cardiac improvement, the patient later developed central nervous system progression and died 10 months after diagnosis due to therapy-related neurotoxicity. Discussion This case highlights a rare presentation of primary cardiac lymphoma manifesting as acute coronary syndrome and atrioventricular block secondary to extrinsic coronary compression. It underscores the importance of multimodality imaging, histological confirmation, and adherence to European Society of Cardiology cardio-oncology guidelines. Early multidisciplinary management is essential to balance effective oncological treatment with cardiovascular safety.