Effect of exercise training on left ventricular remodeling in patients with myocardial infarction and possible mechanisms

BACKGROUND: A growing amount of evidence provides support for the hypothesis that acute myocardial infarction (AMI) patients should go through cardiopulmonary exercise testing (CPET) about 3-5 d after AMI is diagnosed, make reasonable exercising prescription, and conduct exercise training under guidance. AIM: To investigate the effect of exercise training (ET) on left ventricular systolic function and left ventricular remodeling (LVRM) and to study the possible mechanisms of LVRM by the changes of matrix metallopeptidase 9 (MMP-9) and tissue inhibitor of metalloproteinases 1 (TIMP-1) in patients with acute ST-segment elevation myocardial infarction (STEMI). METHODS: Sixty patients with first STEMI undergoing direct percutaneous coronary intervention from February 2008 to October 2008 were randomly assigned to an exercise group (n = 30) and a control group (n = 30). The levels of MMP-9 and TIMP-1 were measured in all patients at 1 d, 10-14 d, 30 d, and 6 mo after admission. Two-dimensional echocardiography and cardiopulmonary exercise testing were done in patients at 10-14 d and 6 mo after admission. RESULTS: There was no significant difference in CPET at baseline between the exercise group and the control group. At 6 mo, the time of exercise, peak and anaerobic threshold values of O(2) uptake, and metabolic equivalents increased in both groups, but markedly increased in the exercise group. At baseline, there were no significant differences in left ventricular ejection fraction (LVEF) between the two groups. At 6 mo, LVEF increased in the exercise group, but not in the control group. At 6 mo, the percentage of patients with positive result of LVRM was 26.6% in the exercise group and 52.6% in the control group (P < 0.05). The levels of plasma MMP-9 and TIMP-1 and the ratio of MMP-9 to TIMP-1 in both groups had no significant difference at 1 d and 10-14 d after AMI, but at 30 d and 6 mo, the levels of plasma MMP-9 and TIMP-1 in the exercise group were significantly lower than those in the control group; the ratio of MMP-9 to TIMP-1 in the exercise group was significantly higher than that in the control group. CONCLUSION: ET under supervision based on home condition in early and recovery stage of AMI can improve exercise cardiopulmonary function and prevent the LVRM. Therefore, it may reduce unfavorable remodeling response by decreasing the levels of plasma MMP-9 and TIMP-1 and adjusting the ratio of MMP-9 to TIMP-1 hereafter.