GSTM1 and atrial fibrillation: At enrolment all patients were stratified by serum sST2 level quartiles (Q1: <11.1 ng/mL; Q2: 11.1–16.8 ng/mL; Q3: 16.8–28.4 ng/mL; Q4: >28.4 ng/mL): higher sST2 level quartiles were significantly associated with AF, HF, older age, lower hemaglobin (Hb), low eGFR, and high CRP levels (Table 5).