Introduction: Data on the change in mitral valve annulus diameter (MAD), and left atrial appendage (LAA) structure and function after transcatheter edge-to-edge repair (TEER) of the mitral valve in patients with secondary mitral regurgitation (MR) are lacking.Aim: To evaluate the change in these parameters just after the clip insertion and its relationship with prognosis in the long term.Material and methods: A total of 50 patients (age: 71.5 ±11.3 years, 70% male) with moderate-to-severe or severe MR were included in the study. Transthoracic (TTE) and transoesophageal echocardiography (TEE) were performed before and after the procedure. Prognostic data were recorded with post-procedure telephone calls and follow-up visits.Results: TEE performed during the procedure showed that LAA contraction and filling velocity significantly increased (p < 0.001 for all). Systolic pulmonary artery pressure (SPAP), MAD, and LAA landing zone dimension significantly decreased (p < 0.001 for all). There was only a significant correlation between the MAD before clip placement and the MAD change after clip placement (r = 0.6, p < 0.001). During a mean follow-up period of 10.5 ±8.9 months, no significant correlation was found between MAD change, LAA contraction and filling velocity change, and LAA landing zone dimension change and rehospitalization, stroke, mortality, and composite outcome.Conclusions: The contraction and filling velocity of LAA, SPAP, MAD, and LAA landing zone dimension changed significantly immediately after the MitraClip procedure. Although these parameters are not related to composite outcome in our study, MAD, LAA diameter, and velocity need to be compared between successful and unsuccessful procedures to predict their clinical relevance.