Postoperative Dialysis in Fontan Patients Undergoing Heart Transplant: How Predictive is the Pretransplant Serum Creatinine?

Background: Fontan patients undergoing heart transplant (HT) appear to require hemodialysis (HD) in the early post-HT period at a rate that is higher than other patients, and often despite relatively preserved estimated renal function pre-HT; but this has not been studied formally.

Methods: The Pediatric Heart Transplant Society (PHTS) database was used to identify all children ≥ 2 years of age with Fontan circulatory failure (FCF) or cardiomyopathy (CM, benchmark lesion) who underwent isolated HT from 2005 to 2019. The primary endpoint was the need for postoperative dialysis, defined as any form of dialysis within the first 30 days post-HT. The secondary outcome was 30-day all-cause mortality. Pretransplant estimated glomerular filtration rate (eGFR) was calculated using the modified Schwartz formula. A subset of patients with available data also had renal function evaluated by a noncreatinine-based method.

Results: Of 1994 children who met the inclusion criteria, 13% had FCF and 87% had CM. While their ages were similar, FCF patients were 11% shorter and 9 kg lighter than their CM counterparts. Prior to transplant, FCF patients had a lower serum creatinine and higher pretransplant eGFR by Schwartz formula compared to DCM patients. The Schwartz eGFR overestimated the measured GFR in a small subset of Fontan patients who had direct measurements. Overall, compared to CM patients, FCF patients had a 4.8-fold higher incidence of any form of posttransplant dialysis (3.8% vs. 0.8%, p < 0.001). Of the FCF patients who required posttransplant dialysis, the 30-day post-HT mortality was 40% vs. 14% in those who did not require dialysis (p = 0.3). Multivariable analysis revealed that pre-HT ECMO and longer CPB times were independently associated with posttransplant dialysis in patients with FCF; there was a trend toward association with higher pre-HT eGFR (p = 0.06).

Conclusion: Serum creatinine pretransplant appears to be a poor predictor of renal replacement post-HT in FCF patients and can grossly overestimate creatinine clearance.