Preservation of the mitral valve (MV) size is essential for valve function, and a reduced MV coaptation-zone area increases the risk of developing functional mitral regurgitation (FMR). We aimed to determine if the MV leaflet and coaptation-zone areas were associated with the severity of atherosclerosis assessed by cardio-ankle vascular index (CAVI) in patients with normal left ventricle (LV) systolic function and size by real-time 3D echocardiography (RT3DE).We performed RT3DE analysis in 66 patients with normal LV size and ejection fraction who underwent 2D echocardiography and CAVI. MV coaptation-zone areas were measured by custom 3D software and indexed by body surface area (BSA). The associations of clinical factors and mean CAVI with MV leaflet and coaptation-zone areas were evaluated by univariable and multivariable linear regression analyses.On univariable analysis, MV leaflet area/BSA was significantly associated with age (r = -0.335, P = 0.0069) and mean CAVI (r = -0.464, P < 0.001), and MV coaptation-zone area was significantly associated with age (r = -0.626, P < 0.001), hypertension (r = -0.626, P < 0.001), dyslipidemia (r = -0.626, P < 0.001), E/e' (r = -0.626, P < 0.001), and CAVI (r = -0.740, P < 0.001). On multivariable analysis, mean CAVI was independently associated only with MV leaflet area/BSA (standardized coefficient = -0.611, P < 0.001) and MV coaptation-zone area/BSA (standardized coefficient = -0.74, P < 0.001).In patients with normal LV systolic function and size, MV leaflet and coaptation-zone areas might be reduced according to advancing atherosclerosis. Patients with atherosclerosis might be at increased risk of developing FMR.