Markers of renal function and acute kidney injury in acute heart failure: definitions and impact on outcomes of the cardiorenal syndrome

Aims Acute kidney injury (AKI) in patients hospitalized for acute heart failure (AHF) is part of the cardiorenal syndrome and has been associated with increased morbidity and mortality. However, definitions and prognostic impact of AKI in AHF have been variable. Cystatin C is a prospective new marker of AKI. The objective of this study was to investigate the use of cystatin C as a marker of early AKI in AHF. Methods and results Patients (n = 292) hospitalized for AHF had measurements of cystatin C on admission and at 48 h. We assessed the incidence of a rise in cystatin C between the two measurements and evaluated the effect of an increase in cystatin C on outcomes up to 12 months. The population was on average 75 years old and 49% were female. On admission, median cystatin C was 1.25 mg/L (interquartile range 0.99-1.61 mg/L). A rise in cystatin C by > 0.3 mg/L within 48 h after hospitalization (AKI(cysC)) occurred in 16% of patients and resulted in 3 days (P = 0.01) longer hospital stay and was associated with significantly higher in-hospital mortality, odds ratio 4.0 [95% confidence intervals (CI) 1.3-11.7, P = 0.01]. During follow-up, AKI(cysC) was an independent predictor of 90 days mortality, adjusted odds ratio 2.8 (95% CI 1.2-6.7, P = 0.02). Conclusions Cystatin C appears to be a useful marker of early AKI in patients hospitalized for AHF. A decline in renal function detected by cystatin C during the first 48 h after hospitalization occurs frequently in AHF and has a detrimental impact on prognosis.