The exact mechanisms underlying the association between RDW and poor prognosis for patients with HF remain unknown at this stage. One suggested hypothesis is that inflammation may bridge the relationship between Gomisin-D higher RDW and poorer HF prognosis. It is well documented that the Lucidenic-acid-E inflammatory response plays a critical role in the development and progression of HF. Inflammatory biomarkers, as indicated by previous evidence, can provide important prognostic information for HF. On the other hand, it is widely accepted that inflammation inhibits erythrocyte maturation and accelerates the migration of reticulocytes into the peripheral circulation, thereby increasing RDW. Indeed, the positive relationships between RDW and inflammatory indices have also been documented. Our previous studies also showed that glucocorticoid, a wellknown anti-inflammatory agent, could reduce the RDW in patients with systemic lupus erythematosus. Together, these findings indicate that inflammation plays an important role in the association between a relatively higher RDW and poor HF prognosis. Further studies are needed to explore the detailed mechanisms of the relationships between RDW and HF prognosis. Compared with traditional prognostic indices, such as BNP, NT-proBNP, midregional pro-atrial natriuretic peptide, and troponins, RDW as a prognostic factor for patients with HF offers at least three advantages. First, it is an inexpensive index. Because blood cell count is a routine test for patients with HF and RDW is a regular hematologic parameter, no additional cost should be needed to introduce RDW into the estimation of HF prognosis. Second, RDW is an easily acquired index, which can be tested even in a community hospital. Third, the lifespan of red blood cells is approximately 130 days, which is much longer than that of natriuretic peptides. Therefore, RDW may have less biological variation, and this characteristic may make its clinical interpretation much easier than the parameters evaluated in traditional HF laboratory tests.The results of our subgroup analyses suggest that follow-up duration is an important source of heterogeneity among the included studies, and the association between a higher RDW and a higher risk for future ACM events seemed to be stronger in studies with longer follow-up durations.