Free-Floating Spherical Left Atrial Thrombus in a Patient With Rheumatic Mitral Stenosis.

• Free-floating left atrial ball thrombus is a rare but life-threatening entity. • Giant LA thrombi may remain asymptomatic despite high-risk features. • Large ball thrombi may not embolize due to inability to cross the MV. • Thrombus formation may occur despite therapeutic warfarin anticoagulation. • Echocardiography is critical for diagnosis and surgical decision-making.