The objective of the present study is to assess the prognostic value of acute kidney injury (AKI) in the evolution of patients with heart failure (HF) using real‐world data.

Patients with a diagnosis of HF and with serial measurements of renal function collected throughout the study period were included. Estimated glomerular filtration rate (GFR) was calculated with the CKD‐EPI (Chronic Kidney Disease Epidemiology Collaboration). AKI was defined when a sudden drop in creatinine with posterior recovery was recorded. According to the Risk, Injury, Failure, Loss, and End‐Stage Renal Disease (RIFLE) scale, AKI severity was graded in three categories: risk [1.5‐fold increase in serum creatinine (sCr)], injury (2.0‐fold increase in sCr), and failure (3.0‐fold increase in sCr or sCr > 4.0 mg/dL). AKI incidence and risk of hospitalization and mortality after the first episode were calculated by adjusting for potential confounders. A total of 30 529 patients with HF were included. During an average follow‐up of 3.2 years, 5294 AKI episodes in 3970 patients (13.0%) and incidence of 3.3/100 HF patients/year were recorded. One episode was observed in 3161 (10.4%), two in 537 (1.8%), and three or more in 272 (0.9%). They were more frequent in women with diabetes and hypertension. The incidence increases across the GFR levels (Stages 1 to 4: risk 7.6%, 6.8%, 11.3%, and 12.5%; injury 2.1%, 2.0%, 3.3%, and 5.5%; and failure 0.9%, 0.6%. 1.4%, and 8.0%). A total of 3817 patients with acute HF admission were recorded during the follow‐up, with incidence of 38.4/100 HF patients/year, 3101 (81.2%) patients without AKI, 545 (14.3%) patients with one episode, and 171 (4.5%) patients with two or more. The number of AKI episodes [one hazard ratio (HR) 1.05 (0.98–1.13); two or more HR 2.01 (1.79–2.25)] and severity [risk HR 1.05 (0.97–1.04); injury HR 1.41 (1.24–1.60); and failure HR 1.90 (1.64–2.20)] increases the risk of hospitalization. A total of 10 560 deaths were recorded, with incidence of 9.3/100 HF patients/year, 8951 (33.7%) of subjects without AKI episodes, 1180 (11.17%) of subjects with one episode, and 429 (4.06%) with two or more episodes. The number of episodes [one HR 1.05 (0.98–1.13); two or more HR 2.01 (1.79–2.25)] and severity [risk 1.05 confidence interval (CI) (0.97–1.14), injury 1.41 (CI 1.24–1.60), and failure 1.90 (CI 1.64–2.20)] increases mortality risk.

The study demonstrated the worse prognostic value of sudden renal function decline in HF patients and pointed to those with more future risk who require review of treatment and closer follow‐up.