EPO and anemia (phenotype): The notion of bone marrow resistance to erythropoietin's effects has been posited as a plausible mechanism for anemia and heightened mortality in selected patients [44] Considering the pivotal role of erythropoietin in averting apoptosis of erythrocyte progenitor cells and invigorating their proliferation, maturation, and terminal differentiation [45], the raised erythropoietin levels may offer an explicable account for elevated RDW levels in HF patients with a more adverse prognosis.