Abstract 4146827: Abnormal Liver Stiffness as a Risk Factor for Elevated Hemoglobin A1c in Patients with Fontan Physiology

Background: Staged surgical palliation resulting in the Fontan operation increases survival in patients born with single ventricle congenital heart disease. Fontan survivors are at higher risk for dysfunction in multiple organ systems. Recent studies have shown higher prevalence of elevated hemoglobin A1c (HbA1c) as a marker of abnormal glucose metabolism in Fontan patients with modifiable associated factors such as obesity and hypertriglyceridemia. However, other risk factors associated with abnormal HbA1c in this population remain unclear. In adults with structurally normal hearts, liver fibrosis and cirrhosis are associated with insulin resistance and elevated HbA1c. One of the known complications of Fontan physiology is elevated systemic venous pressure and resultant liver congestion and fibrosis; however, it is unclear if there is a relationship between liver congestion and abnormal glucose metabolism or insulin resistance in this population. Ultrasound shear wave elastography (SWE) is a non-invasive imaging technique that can quantify the extent of liver fibrosis in patients with structurally normal hearts. Our study aimed to discern a relationship between liver stiffness measured via ultrasound SWE and elevated HbA1c in Fontan patients. Methods: Single-center retrospective cross-sectional cohort study including Fontan patients with documented HbA1c testing and liver stiffness measurement (kilopascals, kPa) measured via SWE. Linear correlation and variable comparisons were examined. Results: Of 414 Fontan patients evaluated at our center, 190 had at least one HbA1c. Abnormal HbA1c ( >5.6%) was found in 36% (n=70). Additionally, 141 patients had at least one ultrasound SWE and were included in our study. 82 (58%) were male, mean age at time of elastography was 19.46 ± 9.70 years, and 59 (42%) were Caucasian. Patients with abnormal HbA1c had a statistically significant higher median liver stiffness as compared to those with normal HbA1c (13.9± 21.0 kPa vs. 8.9 ±3.04 kPa, p=0.024). Conclusion: More than one third of Fontan survivors have abnormal glucose metabolism demonstrated by an elevated HbA1c. Hepatic congestion and fibrosis are known complications of Fontan physiology and increasing liver stiffness by ultrasound elastography may be associated with worsening glucose metabolism. Further investigation is needed to understand how elevated HbA1c and liver stiffness are related and how they affect long-term clinical outcomes in Fontan survivors.