Patients Undergoing LVAD Placement Demonstrate Marked Sarcopenia Leading to Overestimation of Pre-Implant Glomerular Filtration Rate

Evaluation of renal dysfunction (RD) in LVAD candidates usually employs serum creatinine (Cr) based estimates. Cr is influenced by the amount of Cr produced by skeletal muscle. Since cardiac cachexia is common in HF, it is unclear to what degree reduced muscle mass and Cr production will affect estimates of glomerular filtration rate (GFR). We hypothesized that Cr production would be lower than predicted in LVAD candidates resulting in a marked underestimation of RD burden. Consecutive adults undergoing LVAD with 24-hour Cr collections were studied (n=84). Cr production was determined using the 24-hour Cr excretion; measured Cr clearance (CrCl) was calculated using standard clearance equations. Renal function was also estimated using the Cockgroft-Gault (CG), MDRD and CKD-EPI equations. All parameters were indexed to a BSA of 1.73 m2. The mean age was 54.5 ± 13.8 years, 69.0% were male and 48.8% were African American. Despite an elevated BMI of 30.5 ± 7.73 kg/m2, the mean 24 hour Cr excretion was only 1255 ± 465 mg (compared to predicted of 1949 ± 634 mg, p<0.001) confirming marked sarcopenia. Less than 30% of patients’ Cr excretion was in the normal range. Pre-LVAD RD was common with a mean measured CrCl of 50.3 ± 21.6 ml/min/1.73m2. The CG, MDRD and CKD-EPI equations all overestimated GFR by greater than 20% with the CG displaying the greatest median error of 22.6% (12.3-36.3%), p<0.001. This translated into 25-35% of the patients being misclassified (depending on the formula used) into a greater CKD stage than indicated by measured CrCl, particularly in those with Cr excretion <1g/day (Figure 1). Patients undergoing LVAD exhibit decreased Cr production likely as a result of cardiac cachexia. This led to significant overestimates of GFR, as GFR estimation equations assume normal Cr production. Further research is necessary to determine if pre-LVAD evaluation of RD could be improved utilizing non-creatinine based metrics of renal function.