For example, patients with persistent AF were reported to have significantly higher levels of serum CICP, TIMP-1 but lower MMP-1 levels compared with those with paroxysmal AF suggesting that the degree of atrial remodeling is due in part to the type of AF: a recent study reported higher MMP-9 levels in patients with permanent AF compared with with paroxysmal AF [36]. This evidence concerns the gene MMP9 and atrial fibrillation.