Background: The study aim was to investigate the mechanism of mitral regurgitation (MR) in lone atrial fibrillation (AF) patients using three-dimensional (3D) transesophageal echocardiography (TEE).
Methods: A retrospective analysis was conducted of 64 patients with AF and a normal left ventricle, and without prolapse of the mitral valve. Among these patients, significant MR was not identified in 33 cases (AF+MR- group) but was present in 31 cases (AF+MR+ group). The distance from the coaptation to the bending point of the anterior mitral leaflet (AML), where the chorda was attached, was termed the 'bending length'. The ratio of the bending length to the distance from coaptation to anterior mitral annulus was termed the 'bending ratio' (= bending length/coaptation-annulus length). The mitral annular area (MAA) fractional change was defined as follows: (MAA at late systole - MAA at early systole)/MAA at late systole × 100%). Other parameters relating to mitral valve morphology obtained using 3D TEE were measured with commercial software (QLAB, Phillips).
Results: The coaptation length (CL) was smaller in the AF+MR+ group than in the AF+MR- group (p<0.001), and correlated significantly with the anteriorposterior diameter of the mitral annulus (R = 0.286, p = -0.022), MAA at mid-systole (R = -0.269, p = 0.032), MAA fractional change (R = 0.434, p <0.001), and the bending ratio (R = -0.603, p <0.001). With a multivariable analysis, the correlating factors of significant MR in lone AF patients were a decrease in MAA fractional change (p = 0.022) and an increase of the bending ratio (p = 0.009).
Conclusions: Small MAA fractional changes and the distant position of the chordae tendineae on the AML from the coaptation correlated with significant MR in AF patients with normal left ventricular systolic function.