A Giant Free-Floating Left Atrial Thrombus With a Flipper Effect.

BACKGROUND: Left atrial (LA) masses may be diagnostically challenging in patients with atrial fibrillation, previous mitral valve surgery, and severe LA remodeling. CASE SUMMARY: A 77-year-old woman with permanent atrial fibrillation and a bileaflet mechanical mitral prosthesis underwent pacemaker implantation. Predischarge transthoracic echocardiography revealed a large LA mass. Transesophageal echocardiography showed a heterogeneous mobile mass, raising the differential diagnosis of thrombus vs myxoma. After intravenous unfractionated heparin, repeat transesophageal echocardiography demonstrated a giant free-floating mass intermittently impinging on the prosthetic discs without increased transprosthetic gradients. Contrast-enhanced computed tomography showed no postcontrast enhancement. Urgent surgery removed the mass, which was macroscopically consistent with thrombus. DISCUSSION: Serial transesophageal echocardiography, particularly with 3-dimensional imaging, can identify dynamic changes in mass mobility and guide prompt management before embolic or prosthetic obstructive complications occur. TAKE-HOME MESSAGE: A free-floating LA thrombus near a mechanical mitral prosthesis may require urgent surgery despite normal gradient.