Discussion :
Our case report underlines the special need for medical control in patients with mitral valve stenosis and atrial fibrillation because of the high incidence of left atrial thrombi [4,5] . In our patient, the cardiac evaluation revealed a paroxysmal atrial fibrillation with rheumatic mitral valve stenosis.
It is speculated that a fixed thrombus initially forms in the left atrial appendage or the left atrial wall [6] . Afterwards, it grows into a round shape, followed by disconnection of the pedicle between the thrombus and the atrial wall [7] . Wall-adherent thrombi can detach and float freely [8] . The detached thrombus may be remodeled into the spherical shape by the sculpting effect of multiple collisions with the atrial wall and result ball thrombi [9] .
Abe and col advocated the classification of left atrial thrombi into three types; movable ball type, fixed ball type and mountain type. They demonstrated that the rate of embolism in the movable type group was significantly higher than that in the other groups [10] . In our case, it was a movable ball type and the embolic rate was very high[11] , but, among these, spinning ball thrombi may have an even worse prognosis [6] .
The presence of a left atrial ball thrombus is linked to higher embolic rates [12] . Although clinical evidence is sparse, prompt surgical removal of the free floating thrombus, often in conjunction with mitral valve repair or replacement, is the appropriate therapeutic course in most patients [13] because re-embolization on formal anticoagulation has been reported [14] .