Background: Recent data suggest that the mechanisms contributing to ischaemic mitral regurgitation (IMR) in the setting of acute myocardial infarction (MI) are different compared to chronic IMR. However, little is known about the dynamic changes over time of mitral valve (MV) geometry after acute MI. Methods and results:Comprehensive three-dimensional (3D) assessment of the MV geometry was performed in 30 patients in the first 7 days after a first ST elevation myocardial infarction (STEMI), and after 4 years of follow-up. The MV annulus diameters and area remained unchanged over time, however the MA became progressively flatter (mean difference of annular height 0.19±0.33 cm, p<0.05), independently of the presence or severity of IMR. The posterior leaflet length and area got smaller over time (1.53±0.51 cm vs 1.27±0.33 cm; p<0.05 and 5.65±1.58 cm2 vs 4.88±1.65 cm2; p<0.05, respectively). The tenting height and area were smaller at follow-up (9.06±2.6 mm vs 7.84±2.61 mm, p<0.05; and 1.88±0.6 cm2 vs 1.57±0.5 cm2; p<0.05, respectively). A larger tenting at follow-up correlated with 3D left atrial (LA) volumes, but not with LV volumes and ejection fraction. Conclusions: MV geometry changes over time even in patients with non-severe IMR. The MV healing process consists in annulus flattening associated with improved tenting.