Objectives: We aimed to measure changes in the levels of several miRNAs during open-heart surgery and to investigate the relationship between these changes and cardiac biomarkers. Methods: Creatine kinase-muscle band (CK-MB), cardiac troponin (cTnI) and miRNA (miR-1/21/208a/499) levels were measured during open-heart surgery in 15 patients undergoing combined mitral and aortic valve replacement. The levels of these markers were measured presurgically, 45 min after aortic clamping, 60 min after reperfusion and 24 h after surgery. Results: Significant differences were found in miR-1/208a/499 levels but not in miR-21 levels. miR1/208a levels were unchanged until 45 min after aortic clamping, increased 60 min after reperfusion (p < 0.001) and decreased significantly 24 h after surgery (p < 0.001). The changes in miR-1/208a levels exhibited a similar pattern to those observed for cTnI and CK-MB, although the changes in miR-208a levels reflected more rapidly than those in miR-1 levels. miR-499 levels decreased after reperfusion (p < 0.001) until 24 h after surgery; these levels were negatively correlated with cTnI and CK-MB levels at all of the time points. Conclusions: A time-dependent change in miR-1/208a/499 levels occurred during open-heart surgery, and these were associated with levels of cTnI and CK-MB. These results reveal that miRNAs may be sensitive biomarkers for I/R injury during open-heart surgery. (C) 2015 S. Karger AG, Basel