Spontaneous echo contrast (SEC) may be detected by ultrasonography in environments favoring blood stasis. It is most commonly seen through the use of transesophageal echocardiography in the left atrium of patients with rheumatic mitral valve disease especially in the presence of atrial fibrillation. We studied the predictors of SEC, such as cardiac rhythm, left atrium and left atrial appendage functions, and mitral and pulmonary vein flow parameters, in patients with rheumatic mitral valve disease. The relationship between these parameters and the severity of SEC and appearance of thrombus was evaluated.