Fibrosis‐4 index identifies worsening renal function associated with adverse outcomes in acute heart failure

AIMS: Worsening renal function (WRF) often develops during heart failure (HF) treatment. However, prognostic implications of WRF in acute HF remain controversial, and risk stratification of WRF is challenging. Although the fibrosis‐4 index (FIB‐4) was initially established as a liver fibrosis marker, recent studies show that high FIB‐4 is associated with venous congestion and poor prognosis in acute HF. This study aimed to evaluate whether FIB‐4 could identify prognostically relevant and non‐relevant WRF in patients with acute HF. METHODS AND RESULTS: We retrospectively analysed data from a single‐centre registry on acute HF at our university hospital between January 2015 and June 2021. This study included patients with acute HF aged ≥20 years who were immediately hospitalized and had brain natriuretic peptide levels ≥100 pg/mL at admission. WRF was defined as increases of ≥0.3 mg/dL and >25% in serum creatinine level from admission to discharge. FIB‐4 scores were calculated before discharge. The primary endpoint was all‐cause mortality within 1 year of discharge. Based on the presence of WRF and whether FIB‐4 scores were above the median, patients were stratified into four groups: no WRF and lower FIB‐4 scores, no WRF and higher FIB‐4 scores, WRF and lower FIB‐4 scores, and WRF and higher FIB‐4 scores. The patients were followed up via clinical visits or telephone interviews. Clinical outcomes were collected from the electronic medical records. RESULTS: Of the 969 patients hospitalized for acute HF (76 ± 11 years, 59% men), 118 patients (12%) had WRF at discharge. The median (interquartile range) FIB‐4 score at discharge was 2.36 (1.55–3.25). The primary endpoint occurred in 136 patients (14.0%). The 1 year mortality rates were 10.5% in the no WRF and lower FIB‐4 scores (≤2.36) group (n = 428), 16.1% in the no WRF and higher FIB‐4 scores (>2.36) group (n = 423), 12.5% in the WRF and lower FIB‐4 scores group (n = 56), and 25.8% in the WRF and higher FIB‐4 scores group (n = 62) (P = 0.005). Kaplan–Meier analysis demonstrated higher all‐cause mortality in the WRF and higher FIB‐4 group (log‐rank P = 0.003). In the Cox regression analysis, only the WRF and higher FIB‐4 scores group was associated with an increased risk of mortality compared with the no WRF and lower FIB‐4 scores group (hazard ratio = 2.11, 95% confidence interval: 1.07–4.18, P = 0.032), despite adjusting for other confounding factors. CONCLUSIONS: FIB‐4 is a valuable risk stratification marker for WRF in patients with acute HF. The underlying mechanism and potential clinical importance of these observations require further investigation.