Preliminary analysis excluded 11 (10.6%) patients because of suboptimal quality of transthoracic images. In TEE, interob- Figure 2. The scheme of the selection of index beat during AF. The STE results were estimated using the ratio of preceding (1) to pre-preceding (2) R-R′ interval. We selected the beat with the smallest difference between prevenient R-R′ intervals BPM -beats per minute; HR -heart rate; STE -speckle-tracking echocardiography server discrepancies regarding LAAT vs. "sludge" differentiation involved 6 (5.8%) patients. These cases were excluded from further analysis. Finally, we enrolled into the study 36 patients with LAAT and 51 patients without LAAT as controls according to previously established criteria. Demographic, clinical, and echocardiographic **data** for the study group are presented in Table 1.