**Figure 4.** **Echocardiography shows that cardiac function is improved by implanting hAECs and their exosomes in a rat acute myocardial infarction model.** (**A**) Representative M-mode echocardiography of SD rats before and after MI in the hAEC treatment group, exosome group and control group. (**B**) The line charts shows the analysis of the left ventricular ejection fraction (EF), left ventricular fractional shortening (FS), left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD) in SD rats 7, 14 and 28 days after MI, respectively. The data are expressed as the means ± SD, n=8 per group, *P<0.05.