Ischemic mitral regurgitation (MR) is an established adverse prognostic factor after myocardial infarction (MI). Functional ischemic mitral regurgitation in acute phase of MI remains under-investigated due to its often transient and dynamic nature. We aimed to assess left ventricular (LV) mechanics by speckle-tracking echocardiography in acute inferoposterior MI and ischemic mitral regurgitation (MR). METHODS Sixty-nine patients with no structural cardiac valve abnormalities and first acute inferoposterior MI were prospectively enrolled into the study. Two-dimensional transthoracic echocardiography for regional myocardial function and valve assessment was performed within 48 hours of presentation after reperfusion therapy (percutaneous coronary intervention). Based on degree of MR, patients were divided into no significant MR (NMR) group (N = 34, with no or mild (grade 0-I) MR) and ischemic MR (IMR) group (N = 35, with grade ≥2 MR). Thirty-five age- and gender-matched healthy individuals served as a normal reference group. Offline 2D speckle tracking analysis was performed with GE EchoPAC software. RESULTS LV ejection fraction and longitudinal myocardial deformation parameters were significantly better in healthy subjects, but did not differ between both study groups. All circumferential myocardial deformation parameters were significantly worse in IMR group compared to healthy subjects and NMR group. Global, basal, and mid-ventricular radial strain was significantly lower in IMR group compared to both-healthy subjects and NMR group. CONCLUSIONS Ischemic mitral regurgitation in acute inferoposterior MI is associated with worse radial and circumferential LV deformation parameters assessed by 2D speckle tracking echocardiography.