## 4 Discussion
[11] also found values, regarding the MA circumference and longitudinal diameter, of 115 \(\pm\) 18 mm for the MA circumference and 35 \(\pm\) 5 cm for the longitudinal diameter. Interestingly, in the case of our patients who presented with AF, the measurements obtained are also comparable to the values recorded in three-dimensional transesophageal echocardiography (3D-TEE) studies, such as the [PERSON] et al. study [12], which found anMA area of 8.86 \(\pm\) 1.03 cm\({}^{2}\) in the control group without AF, and 12.6\(\pm\) 0.85 cm\({}^{2}\) in the AF + significant mitral regurgitation group; an MA circumference of 10.8 \(\pm\) 0.9 cm in the control group and 13.4 \(\pm\) 1.3 cm in the AF + significant MR group; a transversal diameter of 30.6 \(\pm\) 2.4 mm in the control group and 32.9 \(\pm\) 20.4 mm in the MR+ group; a longitudinal diameter of 36.3 \(\pm\) 2.3 mm in the control group and 41.0 \(\pm\) 3.8 mm in the MR + AF group. In the patients with no-to-mild mitral regurgitation, compared to moderate-to-severe mitral regurgitation, the mitral annulus dimensions were lower, as follows: a transversal diameter of 32.0 vs. 32.9 mm; a longitudinal diameter of 38.3 vs. 41.0 mm; an MV area of 9.58 vs. 12.66 cm\({}^{2}\); a circumference of 11.5 vs. 13.4 cm [12]. The following similar results were obtained by [PERSON] et al. [13], using three-dimensional transthoracic echocardiography: The MA transverse diameter was 34 mm for patients with functional mitral regurgitation and 28 mm in control subjects. The longitudinal diameter was 44 mm in patients with functional MR and 39 mm in control subjects, whilst the circumference was 12.9 mm and 11.2 mm, respectively. The MA area was 12.2 cm\({}^{2}\) and 8.9 cm\({}^{2}\), respectively. Our retrospective analysis shows that the mitral annulus is enlarged in patients with left atrial dilation. While the association between left ventricular dilation and mitral annulus dilation is well understood, the same cannot be said for the mitral annulus alterations caused by left atrial dilation. In 1996, [PERSON] et al. [14] showed that left atrial enlargement increased the size of the mitral annulus. However, due to the lack of technical advancements, the mitral annular area was computed assuming elliptical geometry of the valve and using two diameters from two different echographic views. The mitral valve area was found to be 6.9 cm\({}^{2}\) in patients with an LA diameter <45 mm and 9.2 cm\({}^{2}\) in patients with an LA diameter >45 mm. Furthermore, the longitudinal diameter was 31 mm in the LAD <45 mm group and 35 mm in the LAD >45 mm group. The discrepancies between the results of [PERSON] and our results are most likely due to the fact that only 40.3% of [PERSON]'s patients had atrial fibrillation. It is unclear if this was paroxysmal or persistent, but the authors state that the LA diameter was 40 mm in one half of the group and 53 mm in the other half. In addition, numerous studies have shown that left atrial enlargement itself can contribute to mitral annulus dilation. [PERSON] et al. [15] compared 53 patients with moderate-to-severe type I functional MR and a normal LV ejection fraction during the first AF ablation with a matched AF group with trivial/mild MR. Despite having equal LV size and function, the patients with MR exhibited significantly larger LA and MA dimensions. Persistent AF, age, and isolated MA dilatation were associated with the significance of MR. In the non-recurring AF subgroup, there was a substantial reduction in LA size (LA volume index of 28.2 cm\({}^{3}\)/m\({}^{2}\) vs. 23.9 cm\({}^{3}\)/m\({}^{2}\)) and MA dimensions (3.41 cm vs. 3.24 cm). As a result, rather than being a result of MR, AF may be considered as a promoter of functional MR, conveying its effect through LA and MA dilatation. Another study showed that mitral annulus dilation, due to atrial remodeling in atrial fibrillation, can influence, by itself, the level of mitral regurgitation in time, in patients without any left ventricular pathology.