GSTM1 and heart failure: For example, one study observed no difference in cerebral exercise oxygenation (ΔO2 Hb) or perfusion (ΔtHb) among patients with New York Heart Association (NYHA) class II heart failure and healthy controls, whereas a reduced cerebral oxygenation/perfusion was demonstrated in patients with NYHA class III heart failure vs. the same healthy control group [10].