High Prevalence of Abnormal Hemoglobin A1c in the Adolescent and Young Adult Fontan Population

Little is known about diabetes risk in adolescents and young adults with Fontan palliation. We sought to understand the prevalence of abnormal hemoglobin A1c (HbA1c) in the adolescent and young adult population with Fontan palliation. Between 2015 and 2021, 78 Fontan patients > 10 years of age were seen in our single ventricle clinic; 66 underwent screening with HbA1c. 50% of the study cohort (n = 33) had HbA1c ≥ 5.7%; 2% (n = 1) had HbA1c ≥ 6.5%. There was no correlation between BMI and HbA1c, with no difference in the prevalence of overweight or obesity (BMI ≥ 85th percentile) between those with and without abnormal HbA1c (31% versus 27%, p = 0.69). While 20% of the cohort had a family history of diabetes, there was no difference in family history between those with and without abnormal HbA1c (21% versus 19%, p = 0.85). There were no differences in other risk factors and characteristics (race, glomerular filtration rate, liver function, liver elastography, hematocrit, and years from Fontan surgery) between those with and without abnormal HbA1c. Our results highlight the importance of recognizing that abnormal HbA1c is highly prevalent in the Fontan population. Whether abnormal HbA1c in this population correlates with atherosclerotic cardiovascular disease in adulthood is not known. The mechanism for an abnormal HbA1c in the adolescent and young adult Fontan population remains unclear and further studies are needed.