MMP9 and myocardial infarction: Studies conducted by Jong G. et al. to assess serum concentration and activity of MMP-9 in a group of twenty-eight patients with myocardial infarction (MI) without myocardial infarction and twenty-seven patients with MI and heart failure showed that both tested parameters related to MMP-9 increased significantly (p < 0.01) in the group of patients with MI and failure compared to patients with MI without failure [25].