Correlation between Body Mass Index and Renal Function before and after LVAD: Evidence for Overestimation of Renal Function Using Creatinine in the Advanced Heart Failure Population

Abstract

<h3>Purpose</h3> Measured glomerular filtration rate (GFR) improves initially after left ventricular assist device (LVAD) implantation and then declines. The reasons for this decline are incompletely understood. We hypothesize that the decline in measured GFR after LVAD is associated with the timing of increasing body mass after surgery. <h3>Methods</h3> Patients with a first time continuous-flow LVAD implant at a single center with renal function data and body mass index (BMI) data before and after LVAD were included in the analysis (n=410). GFR at each time point was calculated with CKD-EPI equation. Trends before and after LVAD were computed and plotted using Locally Estimated Scatterplot Smoothing (LOESS). Linear mixed effects modeling was performed to test the association between GFR and BMI accounting for correlated, repeated measures within persons. <h3>Results</h3> Plots of GFR and BMI before and after LVAD implantation are displayed (Figure). BMI decreased prior to LVAD, decreased further after LVAD, and then steadily increased. GFR declined in the cohort prior to LVAD, improved with medical optimization, improved further post LVAD, and then declined again. Across the cohort there was a strong association between GFR and BMI (p<.001). Each 0.5 unit increase in BMI was associated with a 2.7 unit decrease in GFR. <h3>Conclusion</h3> The displayed trends suggest GFR is over-estimated in the late stages of heart failure and in the immediate post LVAD period due to low creatinine production from sarcopenia. Use of creatinine in the advanced heart failure population may lead to inaccurate GFR estimates. This has broad implications for treatment of the heart failure population.