Hepatic Steatosis in Patients With Single Ventricle and a Fontan Circulation

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.

Hepatic and Renal Consequences of Single Ventricle Physiology Palliated with the Fontan Operation

Over time the long-term survival has dramatically increased for patients with complex congenital heart disease who undergo the Fontan operation. With this increased survival, it has become apparent that such a circulation has important consequences for other organ systems, particularly the liver and kidney. The adverse milieu created by chronic venous hypertension, low cardiac output and an inflammatory state contribute to the pathologic changes observed in the liver and kidneys over the long-term in Fontan patients. The clinical importance of these hepatic and renal comorbidities have only recently begun to be recognized in the context of increasing life expectancy in this population. The objectives of this review are: i) to provide an overview of the pathophysiology of the Fontan circulation and how liver and kidney disease evolve in this setting; ii) to summarize the current evidence base as it relates to the diagnostic approach to liver and kidney disease in Fontan patients; and, iii) to discuss the therapeutic approaches to Fontan associated liver and kidney disease. Given that this is a very active area of research in congenital heart disease, we have identified knowledge gaps and priority research areas to improve the care of Fontan patients. These include: i) establishing the optimal diagnostic tests to detect and track liver and kidney disease change over time,; ii) determining what treatable risk factors contribute to the development of liver and kidney disease; and, iii) evaluating therapies to prevent or slow progression of liver and kidney disease.

Hepatic Steatosis in Patients With Single Ventricle and a Fontan Circulation

Background

Hepatic steatosis, caused by nonalcoholic fatty liver disease, is a leading cause of chronic liver disease. The interplay between hepatic steatosis and the development of liver disease following the Fontan procedure is not well understood. This study examined the prevalence and associations of hepatic steatosis in patients with a Fontan circulation.

Methods and Results

This was a single‐center retrospective study of 95 patients with a Fontan circulation with liver magnetic resonance imaging performed between 2012 and 2019. The average age at magnetic resonance imaging was 21.5±8.5 years. The percent liver fat signal was determined using magnetic resonance chemical shift‐encoded proton density fat fraction imaging. Hepatic steatosis was defined as liver fat ≥5% and was present in 10.5% of the cohort. The presence of hepatic steatosis was associated with higher body mass index (29±4 versus 24±6 kg/m², P=0.006), a higher frequency of obesity (50% versus 12%, P=0.015), lower high‐density lipoprotein cholesterol (35±9 versus 43±14 mg/dL, P=0.050), and greater subcutaneous fat thickness (2.6±0.7 versus 1.8±1.0 cm, P=0.043). There was no association between hepatic steatosis and cardiovascular imaging or hemodynamic variables from cardiac catheterization.

Conclusions

Risk factors for hepatic steatosis in patients with Fontan circulation include obesity and dyslipidemia, similar to what is seen in the general population. Fontan hemodynamics were not associated with hepatic steatosis.