This is a post hoc analysis of the Placebo-controlled Randomized Study of the Selective A1 Adenosine Receptor Antagonist Rolofylline for Patients Hospitalized with Acute Heart Failure and Volume Overload to Assess Treatment Effect on Congestion and Renal FuncTion (PROTECT) trial, a randomized, double-blind, placebo-controlled, multi-center study that enrolled 2033 patients admitted for acute decompensated heart failure, randomized 2:1 to rolofylline, with neutral overall results. Study design, inclusion, and exclusion criteria and results have been published previously . The trial was approved by all local Ethics Committees and conducted in accordance with the Declaration of Helsinki (NCT00328692 and NCT00354458). All patients provided written informed consent. Of the patients who remained hospitalized for at least 4 days (n = 1681), those with available NGAL and creatinine values at baseline (n = 1470), and at least one follow-up measurement for each marker during the first 4 days, were included in the analysis, resulting in a study population of 1447 patients. Patients who had already developed WRF by day 2 (n = 101) were excluded from analyses of the effects of biomarker levels and changes on day 2.