Right Atrial Thrombus Masquerading as Myxoma

In-situ right atrial (RA) thrombus is a rare occurrence typically associated with heightened inflammatory or hypercoagulable states. Here, we present a case of in-situ RA thrombus mimicking atrial myxoma in a patient with sepsis and bacteraemia.

A 41-year-old man presented with septic arthritis and bacteraemia caused by methicillin-resistant Staphylococcus aureus (MRSA). A transoesophageal echocardiogram revealed a large pediculated mass resembling atrial myxoma, which was not visible on transthoracic echocardiography performed four days earlier. Cardiac magnetic resonance (CMR) imaging strongly suggested a thrombus, leading to the patient undergoing transcatheter aspiration. Subsequent pathology confirmed an organised fibrin thrombus without evidence of infection.

The patient's in-situ RA thrombus likely developed in response to a heightened inflammatory state associated with sepsis. Limited data exist on in-situ RA thrombi in the absence of atrial fibrillation, though some reports suggest a correlation between heightened inflammation and a hypercoagulable state.

CMR imaging is invaluable for characterising such masses and can aid in distinguishing a thrombus from a myxoma.

Differentiating right atrial (RA) thrombus from myxoma: cardiac magnetic resonance imaging is essential for distinguishing RA thrombus from myxoma, preventing unnecessary surgeries.Hypercoagulable and inflammatory states: spontaneous in-situ RA thrombi can occur without deep vein thrombosis (DVT) or atrial fibrillation, especially in hypercoagulable and inflammatory conditions.Transcatheter aspiration: this less invasive alternative to surgery is effective for large, mobile RA thrombi, reducing embolisation risk.