GDF15 and atrial fibrillation: Among the potential novel biomarkers, TIMP-1 was significantly higher in the AF recurrence group compared to the SR maintenance group, whereas levels of PAI-1 activity, sST2, GAL-3, IL-6, MMP-9, GDF-15, TGF-β1, and FGF-23 did not differ among the groups (Table 4).