Little is known about diabetes risk in adolescents and young adults with Fontan circulation. We sought to understand the prevalence of abnormal hemoglobin A1c (HgA1c) 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 HgA1c. 50% of the study cohort (n=33) had HgbA1c >5.7%; 2% (n=1) had HgbA1c >6.5%. There was no correlation between BMI and HgbA1c, with no difference in the prevalence of overweight or obesity (BMI >85 th percentile) between those with and without abnormal HbgA1c (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 HgbA1c (21% versus 19%, p=0.85). There were no differences in other risk factors and characteristics (race, GFR, liver function, lipid panel, hematocrit, and years from Fontan surgery) between those with and without normal HgbA1c. Our results highlight the importance of recognizing that abnormal HbA1c is highly prevalent in the Fontan population. Whether abnormal HgA1c in this population correlates with atherosclerotic cardiovascular disease in adulthood is not known. Prior studies have suggested an association among metabolic syndrome, activation of the renin-angiotensin system, chronic liver disease, chronic kidney disease, and reduced muscle mass with impaired glucose tolerance in the adult Fontan population. The mechanism for an abnormal HgA1c in the adolescent and young adult Fontan population remains unclear and further studies are needed.

Little is known about diabetes risk in adolescents and young adults with Fontan circulation. We sought to understand the prevalence of abnormal hemoglobin A1c (HgA1c) 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 HgA1c. 50% of the study cohort (n=33) had HgbA1c >5.7%; 2% (n=1) had HgbA1c >6.5%. There was no correlation between BMI and HgbA1c, with no difference in the prevalence of overweight or obesity (BMI >85th percentile) between those with and without abnormal HbgA1c (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 HgbA1c (21% versus 19%, p=0.85). There were no differences in other risk factors and characteristics (race, GFR, liver function, lipid panel, hematocrit, and years from Fontan surgery) between those with and without normal HgbA1c. Our results highlight the importance of recognizing that abnormal HbA1c is highly prevalent in the Fontan population. Whether abnormal HgA1c in this population correlates with atherosclerotic cardiovascular disease in adulthood is not known. Prior studies have suggested an association among metabolic syndrome, activation of the renin-angiotensin system, chronic liver disease, chronic kidney disease, and reduced muscle mass with impaired glucose tolerance in the adult Fontan population. The mechanism for an abnormal HgA1c in the adolescent and young adult Fontan population remains unclear and further studies are needed.