Rapid Postoperative Progression of Primary Right Atrial Synovial Sarcoma: Transthoracic Echocardiographic Assessment of Hemodynamically Significant Tricuspid Inflow Obstruction

Primary cardiac synovial sarcoma is an exceptionally rare and aggressive malignancy in which complete surgical resection is often difficult. We report a 44-year-old man who presented in cardiogenic shock and underwent emergency resection of a right atrial tumor; histopathology confirmed high-grade biphasic synovial sarcoma with SS18 rearrangement. Early postoperative computed tomography showed a small residual component along the superior vena cava. Within two months, contrast-enhanced computed tomography demonstrated marked progression into the right atrium, with venous thrombosis, pulmonary embolism, pleural effusions and pericardial effusion. Transthoracic echocardiography subsequently showed a 60 × 38 mm right atrial mass causing hemodynamically significant functional tricuspid inflow obstruction, with a mean diastolic transtricuspid gradient of 8.7 mmHg averaged over five measurements at a mean heart rate of 129 beats/min. Echocardiography documented the functional significance of the intracardiac obstruction before urgent repeat surgery, whereas computed tomography defined its anatomical extent and associated extracardiac findings. Follow-up CT showed postoperative residual disease, and pulmonary nodules suspicious for metastatic spread were subsequently identified; the response to oncologic treatment could not be established from the available imaging. This case highlights the complementary anatomical and hemodynamic roles of computed tomography and echocardiography in rapid postoperative progression of primary cardiac synovial sarcoma.