Coronary sinus obstruction by primary cardiac lymphoma as a cause of dyspnea due to significant diastolic dysfunction and elevated filling pressures.

A 52-year-old woman presented with severe dyspnea of 2 weeks' duration. Echocardiography showed an enlarged left atrium but normal global left ventricular systolic function. However, a huge, irregularly shaped mass at the dilated coronary sinus that extended into the right atrium was noted. Mitral inflow showed restrictive physiology and the E/E' ratio was significantly elevated, suggesting elevated left ventricular filling pressures. Echocardiography-guided biopsy was performed, and a diagnosis of primary cardiac lymphoma (diffuse large B-cell type) was made. After the first cycle of chemotherapy, the patient's symptom was markedly improved. A follow-up echocardiogram showed complete removal of the mass and a change in left ventricular filling pattern from restrictive to relaxation abnormality with decreased E/E'. The present case demonstrates a rare cause of diastolic dysfunction due to coronary sinus obstruction by tumor infiltration. Diastolic dysfunction caused by coronary sinus obstruction was improved after the tumor was resolved by chemotherapy.