GSTM1 and congestive heart failure: In a clinical study on ESA treatment in 319 patients with chronic heart failure, the ESA improved the Hb levels from 11.3 to 13.4 g/dL, but did not significantly improve the exercise tolerance, NYHA class, or quality of life; however, the exercise time was reported to be significantly longer in patients whose serum Hb levels increased by 12.0 g/dL or more [6].