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Background: Estimated glomerular filtration rate (eGFR) based on serum creatinine (sCr) improves early after left ventricular assist device (LVAD) implantation but subsequently declines. Although sCr is a commonly accepted clinical standard, cystatin C (CysC) has shown superiority in assessment of renal function in disease states characterized by muscle wasting. Among patients with an LVAD, we aimed to (1) longitudinally compare CysC-eGFR and sCr-eGFR, (2) assess their predictive value for early postoperative outcomes, and (3) investigate mechanisms which might explain potential discrepancies. Methods: A prospective cohort (n=116) with CysC and sCr concurrently measured at serial time points, and a retrospective cohort (n=91) with chest computed tomography performed within 40 days post-LVAD were studied. In the prospective cohort, the primary end point was a composite of in-hospital mortality, renal replacement therapy, or severe right ventricular failure. In the retrospective cohort, muscle mass was estimated using pectoralis muscle area indexed to body surface area (pectoralis muscle index). Results: In the prospective cohort, sCr-eGFR significantly improved early post-LVAD and subsequently declined, whereas CysC-eGFR remained stable. CysC-eGFR but not sCr-eGFR predicted the primary end point: odds ratio per 5 mL/(min·1.73 m 2 ) decrease 1.16 (1.02–1.31) versus 0.99 (0.94–1.05). In retrospective cohort, for every 5 days post-LVAD, a 6% decrease in pectoralis muscle index was observed (95% CI, 2%–9%, P =0.003). After adjusting for time on LVAD, for every 1 cm 2 /m 2 decrease in pectoralis muscle index, there was a 4% decrease in 30-day post-LVAD sCr (95% CI, 1%–6%, P =0.004). Conclusions: Initial improvement in sCr-eGFR is likely due to muscle wasting following LVAD surgery. CysC may improve assessment of renal function and prediction of early postoperative outcomes in patients with an LVAD.

Aims Acute heart failure (HF) is associated with muscle mass loss, potentially leading to overestimation of kidney function using serum creatinine‐based estimated glomerular filtration rate (eGFRsCr). Cystatin C‐based eGFR (eGFRCysC) is less muscle mass dependent. Changes in the difference between eGFRCysC and eGFRsCr may reflect muscle mass loss. We investigated the difference between eGFRCysC and eGFRsCr and its association with clinical outcomes in acute HF patients. Methods and results A post hoc analysis was performed in 841 patients enrolled in three trials: Diuretic Optimization Strategy Evaluation (DOSE), Renal Optimization Strategies Evaluation (ROSE), and Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARRESS‐HF). Intra‐individual differences between eGFRs (eGFRdiff) were calculated as eGFRCysC–eGFRsCr at serial time points during HF admission. We investigated associations of (i) change in eGFRdiff between baseline and day 3 or 4 with readmission‐free survival up to day 60; (ii) index hospitalization length of stay (LOS) and readmission with eGFRdiff at day 60. eGFRCysC reclassified 40% of samples to more advanced kidney dysfunction. Median eGFRdiff was −4 [−11 to 1.5] mL/min/1.73 m2 at baseline, became more negative during admission and remained significantly different at day 60. The change in eGFRdiff between baseline and day 3 or 4 was associated with readmission‐free survival (adjusted hazard ratio per standard deviation decrease in eGFRdiff: 1.14, P = 0.035). Longer index hospitalization LOS and readmission were associated with more negative eGFRdiff at day 60 (both P ≤ 0.026 in adjusted models). Conclusions In acute HF, a marked difference between eGFRCysC and eGFRsCr is present at baseline, becomes more pronounced during hospitalization, and is sustained at 60 day follow‐up. The change in eGFRdiff during HF admission and eGFRdiff at day 60 are associated with clinical outcomes.

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