GSTM1 and atrial fibrillation: Patients with AF had significantly higher levels of Hb than the SR group: the SR group, 144 (135–155) g/l; the persistent AF group, 152 (142–162.0) g/l, p  <  0.001; and the paroxysmal AF group, 148 (139–160) g/l, p = 0.012.