Data have shown that high levels of TMAO (TMAO ≥ 61.8 ng/mL, OR 2.88 with p = 0.006) might increase the risk of POAF regardless of preoperative anemia (Hb < 13.1 g/dL, OR 2.37 with p = 0.033) and reduced right ejection fraction (TAPSE < 20 mm, OR 2.38 with p = 0.017). The gene discussed is GSTM1; the disease is anemia.