Renal tubular damage and clinical outcome in heart failure with preserved ejection fraction and chronic kidney disease

AIMS: Despite advances in heart failure (HF) treatment, HF with preserved ejection fraction (HFpEF) remains a health problem with a high mortality rate. HFpEF is composed of diverse phenogroups, of which patients with concomitant renal impairment have worse outcomes. Renal tubular damage (RTD) is associated with the development of HF and chronic kidney disease (CKD). However, the impact of RTD on HF progression in patients with HFpEF and CKD remains unclear. The aim of the present study was to examine whether RTD could predict HF‐related events in patients with HFpEF and CKD. METHODS AND RESULTS: We measured RTD markers, such as urinary β(2)‐microglobulin to creatinine ratio (UBCR) and N‐acetyl‐β‐d‐glucosamidase (NAG) level, in 319 consecutive patients with HFpEF and CKD who were hospitalized for acute HF (49% females, mean age 76 ± 12). Based on previous reports, high UBCR and high NAG levels were defined as UBCR ≥300 μg/gCr and NAG >14.2 U/gCr, respectively. There were 91 HF‐related events, defined as HF hospitalizations or HF deaths, during the median follow‐up period of 5.2 years. The prevalence of high UBCR increased with advancing New York Heart Association functional class and albuminuria. Kaplan–Meier analysis demonstrated that patients with high UBCR had more HF‐related events than those with normal or low UBCR. Multivariate Cox proportional hazards regression analyses demonstrated that high UBCR, but not high NAG level, was an independent predictor of HF‐related events after adjusting for confounding risk factors in patients with HFpEF and CKD (hazard ratio, 2.60; 95% confidence interval, 1.52–4.72; P = 0.0009). UBCR significantly improved the C‐statistic, with a significant net reclassification index and integrated discrimination improvement (0.738 vs. 0.684; P = 0.0244). CONCLUSION: RTD, as assessed by a high UBCR, was associated with the severity and clinical outcomes of HFpEF and CKD, indicating that it could be a feasible marker for HF progression.