Insulin Resistance after Fontan Palliation

Patients with a single ventricle heart who had Fontan palliation (S/P Fontan) are at increased risk for acquired morbidity. Insulin resistance (IR) is a predictor of cardiac morbidity and mortality. A single-center, cross-sectional study using S/P Fontan and controls was designed to assess IR S/P Fontan. Group comparisons were made in IR via the Quantitative Insulin Index (QUICKI) and the natural log-transformed homeostasis model assessment, ln (HOMA-IR), without/with adjusting for age. A total of 89 patients (59 Fontan and 30 controls) were included. Fontan patients showed a significant decrease in QUICKI (0.34 ± 0.03 vs 0.37 ± 0.02) and an elevation of ln (HOMA-IR) (0.82 ± 0.62 vs 0.24 ± 0.44) compared to controls (both p < 0.0001); this remained significant even adjusting for age. With older age, there was a significant, progressive decrease in QUICKI (p = 0.01) and an increase in ln (HOMA-IR) (p = 0.02) S/P Fontan. Analysis excluding Fontan patients with obesity still showed a significant reduction of QUICKI and an elevation of ln (HOMA-IR) in Fontan patients compared to controls when adjusting for age (both p < 0.05). Using QUICKI, IR was present in 41 (69.5%) Fontan patients vs. 3 (10%) controls (p < 0.0001) and using HOMA-IR, IR was present in 32 (54.2%) vs 5 (16.7%) controls (p = 0.001). Fontan patients had significantly more IR compared to controls and the prevalence of IR increases with age. Since IR is known to correlate with long-term morbidity and mortality and can be ameliorated by therapies, we believe it is critical that IR be identified as early as possible in Fontan patients.