Aims: Chronic heart failure is often accompanied by chronic kidney disease (CKD). Interdependency of both is described as cardiorenal syndrome. Plasmatic NT-proBNP represents an established marker for heart failure. Previous studies suggested urinary NT-proBNP has potential as marker of chronic heart failure as well. The aim of this study was to assess the prognostic capability of urinary NT-proBNP regarding cardiorenal syndrome, especially regarding progression of CKD in patients with ICD and chronic heart failure.

Methods: 313 ICD patients were included in the study. NT-proBNP was assessed in plasmatic and fresh spot urine. Urinary NT-proBNP was normalized to urinary creatinine. Follow up was performed after 51 months (IQR 25-55) and the progress of renal function was evaluated by semiannual glomerular filtration rate (eGFR CKD-EPI) values. Further, data regarding ICD shock therapies and all cause mortality were obtained. Outcomes of interest were continuous progression of CKD and a combined endpoint of continuous progression of CKD, ICD shock therapies and all-cause mortality. Continuous progression of CKD was defined by consistent decline in eGFR category accompanied by a ≥ 25% drop of baseline eGFR.

Results: Average four (IQR 2-6) follow up values of serum creatinine per patient were obtained. CKD was evident in 127 patients (40.6%). During follow up 29 patients (9.3%) developed a continuous progression of CKD. Plasmatic NT-proBNP as well as urinary NT-proBNP were significantly elevated in patients with continuous progression of CKD (p < 0.001). According to Kaplan Meier analysis, plasmatic NT-proBNP ≥ median as well as urinary NT-proBNP ≥ median were significant predictors for continuous CKD progression and the combined endpoint (each p < 0.01). In Cox regression analysis, plasmatic as well as urinary NT-proBNP were independent predictors for continuous CKD progression, beside diabetes and serum creatinine (each p < 0.02). Further, plasmatic as well as urinary NT-proBNP were independent predictors for the combined endpoint (each p < 0.02).

Conclusion: Urinary NT-proBNP and plasmatic NT-proBNP show similar prognostic capabilities regarding prognosis of the cardiorenal syndrome, especially regarding progression of CKD.