Introduction: Dilation of left atrium (LA) is closely related to atrial fibrillation (AF). The mechanism of LA dilation was not fully explained. Some observations indicate that this process may be reversible, and its condition is the control of arrhythmia. Material and method: The study was conducted on the group of 30 subjects including 18 men and 12 women aged 52Ð86 years (mean age 63.81±9.22 years) with non-rheumatic AF. Echocardiography was performed before AF control, immediately after sinus rhythm (SR) was obtained as well as after 6-month-observation with preserved SR. The following parameters were assessed during transthoracic echocardiography: LAmax , LAlength , LAwidth , LAcircum , LAarea , LAmin , LAP , PEPLA , ETLA , PEPLA/ETLA ,SFLA , FBOLA , FCLA , IELA , E amplLV , E intgLV , A amplLV , A intgLV , MV intgLV , A amplLV/E amplLV , A intgLV/MV intgLV . In transesophageal investigation, PVA, PVA intg, PVAtime were estimated. Results: Directly after AF control, LA dimensions did not change significantly in comparison to the time of arrhythmia. They decreased considerably during long-lasting SR maintenance. These changes were accompanied by the improvement of LA haemodynamic function reflected mainly in the increase of shortening fraction and ejection fraction from 7.34±3.82%; 14.0±4.6%, respectively just after SR was obtained to 13.82±6.74%; 21.37±7.57%, respectively in long-term observation. Doppler parameters concerning active LA contraction in the flow through mitral valve and recorded in left superior pulmonary vein were also greatly improved during long-lasting SR maintenance. Conclusions: SR restoration and its long-lasting maintenance results in the decrease of LA dimensions and the improvement of its function. Simultaneous use of parameters characterising LA function recorded from mitral flow and the flow through pulmonary veins is a credible marker of the restoration of LA mechanical function after FA reversion to SR.

Keywords: Echocardiography, cardioversion, Atrial Fibrillation, atrial tachycardiomyopathy