GSTM1 and hydrops fetalis: In patients with cyanotic congenital heart disease who were polycythemic and had ID, oral iron improved the Hb, the QoL and the 6 Minute Walking Distance as well as serum ferritin and %TSat, but not peak VO2 [64] This uncertainty about which treatment to use initially, oral or IV iron, is reflected in expert reviews in HF, some of which recommend starting with oral iron [5] and some with IV iron [7].