Development of a left atrial ball thrombus in a woman with complex congenital heart disease including congenital mitral valve stenosis.

A 20-year-old woman with complex cyanotic congenital heart disease, including severe congenital mitral stenosis and intact atrial septum, who developed a left atrial ball thrombus and an embolic phenomenon, is presented. Increased vigilance in this unique setting is necessary for the antemortem detection of this rare complication.