Coronary microembolization (CME) is responsible for a substantial fraction of microvascular obstruction (MVO), which are strongly associated with mortality and hospitalization for heart failure within 1 year after primary percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI). However, the effect of miRNA on cardiomyocyte apoptosis in a CME model has been less well-studied. miRNA sequencing analysis was performed to examine differentially expressed miRNAs induced by CME in rats. Phosphatase and tensin homologue (PTEN) 3 'RACE and dual-luciferase reporter assays were performed to confirm that PTEN is a direct target gene of miR-486-5p. miRNA-486-5p overexpression was established by injecting AAV into rats via the tail vein. The CME model was established by injecting microspheres into the left ventricle of rats. 6h after surgery, cardiac function, microinfarct area, and the apoptotic index were determined. RT-PCR was used to evaluate mRNA level and Western blotting was used to evaluate protein expression. miRNA sequencing data showed that there were 5 upregulated and 8 downregulated miRNAs, and the relative expression of miRNA-486-5p was significantly downregulated. PTEN 3'RACE and dual-luciferase reporter assays confirmed that miR-486-5p directly targets the rat PTEN gene. The expression of miR-486-5p gradually declined, however, the expression of PTEN mRNA rapidly increased at early time points after CME. Overexpression of miR-486-5p reduced cardiomyocyte apoptosis and improved cardiac function through inhibition of PTEN and activation of the PI3K/Akt pathway in rat CME models. Overexpression of miR-486-5p, which targets PTEN, protects against CME-induced cardiomyocyte apoptosis and improves cardiac function in rats by activating the PI3K/Akt pathway.