Left ventricular (LV) pressure-strain loops (PSLs) have been recently validated as a non-invasive index of myocardial performance. The present study sought to analyze variation in LV function, myocardial work, and energy dispersion in patients with severe mitral regurgitation undergoing percutaneous mitral valve repair (MitraClip ® system) or mitral valve surgery (MVS). Thirty-two patients (mean age: 71 ± 10 years) with severe MR (18 with ischemic cardiomyopathy, 14 with dilated cardiomyopathy) and a LVEF < 50% undergoing MitraClip ® implantation and 15 patients (mean age: 64 ± 13 years) with primary MR and LVEF > 50% undergoing MVS according to ESC guidelines were included in the study. All patients underwent standard and speckle tracking echocardiography (STE) before MitraClip ® /MVS and at 6-month follow-up. Strain traces and valvular event times were used to calculate LV-PSLs and Global cardiac Work (GW), Positive Work (PW), and Negative work (NW) were therefore obtained. As showed in Table 1 , patients undergoing MVS experienced a decrease in LVEF, mechanical dispersion and an increase in cardiac NW after surgery. In patients undergoing MitraClip ® , a similar result was obtained when baseline LVEF was > 40%, whereas patients having a baseline LVEF < 40% did not experience significant changes in LV performance and mechanical dispersion. In patients with severe MR and a LVEF > 40%, either MitraClip ® or MVS have a negative impact on LV performance. The significant increase in mechanical dispersion and negative work, detected by new STE-derived analysis, provides an interesting explanation of these findings.