The report has dealt with the role of transesophageal echocardiography (TEE) when establishing the etiology of ischemic cerebral infarction, and with studying patients having a demonstrable thrombus in the left atrium. A set consists of 237 patients (148 men, 89 women), aged 20 – 80 years (mean age 58 yrs) with ischemic cerebral infarction (confirmed by CT examination) with sinus rhythm without demonstrated extracardial causes. The patients with a revealed thrombus were given anticoagulation treatment and were examined repeatedly. 26.5% patients showed a cardial thrombus as a probable cause of ischemic cerebral infarction, 8.26% displayed spontaneous echocontrast. The foramen ovale apertum was found in 5.7% patients, a defect of the atrial septum in 1.68%, the atrial septum aneurysm in 2.10%, hypokinesis of the left ventricle wall in 10.97%, and sclerotic plates within the aorta in 27.8% patients. The output velocity in the left atrial auricle differed statistically significantly (p = 0.042) between a set with (Group A) and that without a thrombus (Group B). Group A (63 patients) was examined repeatedly (the 2nd examination was carried out after 8.36 months (median 7, SD 3.2), the 3rd examination after 8.5 months (median 7, SD 4.7). The repeated finding of a thrombus (the 2nd examination 52.38%, the 3rd examination 44.44% patients) was surprising. All the patients with confirmed ischemic cerebral infarction and clinical suspicion of a cardiogenic embolizing cause should be indicated for TEE examination. Questionable is the indication for examinations in patients who had negative finding in TEE as well as clear indication for a long-termed anticoagulation therapy (e.g. chronic FS) and without history of paradoxical embolization. This method is suitable for studying the treatment efficacy.

        Key words: transesophageal echocardiography, ischemic cerebral infarction, thrombi in the left atrium, output velocity in the left atrium auricle