Abstract 9847: Glomerular Filtration Rate in Pediatric Heart Transplant Recipients Can be Measured During Routine Catheterization and is Best Estimated by the Full CKiD Formula

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Identification of chronic kidney disease (CKD) after pediatric heart transplantation (PHT) is limited by inaccuracies in creatinine-based estimates of glomerular filtration rate (GFR); iohexol plasma clearance is a proven method of measuring GFR. We hypothesized that GFR can be measured by a modified iohexol clearance protocol during routine coronary angiography in PHT recipients, and that the recently developed CKiD GFR estimating formula, utilizing serum creatinine and cystatin C, provides a better estimate of GFR than creatinine or cystatin equations alone. We performed a cross-sectional study of PHT recipients, ages 2-18 yrs, undergoing surveillance coronary angiography. GFR was measured by obtaining iohexol levels at 2, 4, and 5 hours post-iohexol infusion for angiography, then calculating area under the curve of iohexol disappearance from plasma. Agreement between measured GFR and multiple GFR estimating equations was assessed with Bland Altman plots, correlation, and % of estimates within +/- 10 and 30% of measured GFR. Of 40 enrolled subjects, 31 had complete GFR data. Median age was 15.0 yrs [IQR 7.6, 16.6], time since HT was 5.9 yrs [2.0, 10.8], height %ile was 26 (7, 48), serum creatinine was 0.7 (0.5, 0.8) mg/dL, cystatin C was 0.83 (0.72, 0.91) mg/L, and measured GFR was 89.5 (78.7-107.0) ml/min/1.73m 2 (mean 93.8, SD22.5). A comparison of measured GFR to estimated GFR is shown in Table 1; the full CKiD formula showed best agreement with measured GFR. Conclusions: 1. We describe a novel modified iohexol plasma clearance method to measure GFR in PHT recipients undergoing coronary angiography. 2. Measured median GFR in this cohort is 89.5 ml/min/1.73m2, suggesting early CKD. 3. The full CKiD formula performs best with respect to bias, accuracy, and correlation.