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

Noninvasive Advanced Cardiovascular Magnetic Resonance-Derived Fontan Hemodynamics Are Associated With Reduced Kidney Function But Not Albuminuria

BACKGROUND

Kidney disease is the most important predictor of death in patients with a Fontan circulation, yet its clinical and hemodynamic correlates have not been well established.

METHODS AND RESULTS

A total of 53 ambulatory patients with a Fontan circulation (median age, 16.2 years, 52.8% male patients) underwent advanced cardiovascular magnetic resonance assessment, including 4-dimensional flow imaging and computational fluid dynamics. Estimated glomerular filtration rate (eGFR) <90 mL/min per 1.73 m2 was observed in 20.8% and albumin-to-creatinine ratio >3 mg/mmol in 39.6%. The average eGFR decline rate was -1.83 mL/min per 1.73 m2 per year (95% CI, -2.67 to -0.99; P<0.001). Lower eGFR was associated with older age, larger body surface area at examination, longer time since Fontan procedure, and lower systemic ventricular ejection fraction. Higher albumin-to-creatinine ratio was associated with absence of fenestration at the Fontan operation, and older age and lower systemic ventricular ejection fraction at the assessment. Lower cross-sectional area of the Fontan conduit indexed to flow (r=0.32, P=0.038), higher inferior vena cava-conduit velocity mismatch factor (r=-0.35, P=0.022), higher kinetic energy indexed to flow in the total cavopulmonary connection (r=-0.59, P=0.005), and higher total cavopulmonary connection resistance (r=-0.42, P=0.005 at rest; r=-0.43, P=0.004 during exercise) were all associated with lower eGFR but not with albuminuria.

CONCLUSIONS

Kidney dysfunction and albuminuria are common among clinically well adolescents and young adults with a Fontan circulation. Advanced cardiovascular magnetic resonance-derived metrics indicative of declining Fontan hemodynamics are associated with eGFR and might serve as targets to improve kidney health. Albuminuria might be driven by other factors that need further investigation.

Long-Term Renal Involvement in Association with Fontan Circulation

Multiorgan dysfunction is a concern of Fontan patients. To clarify the pathophysiology of Fontan nephropathy, we characterize renal disease in the long-term observational study. Medical records of 128 consecutive Fontan patients [median age: 22 (range 15-37) years old] treated between 2009 and 2018 were reviewed to investigate the incidence of nephropathy and its association with other clinical variables. Thirty-seven patients (29%) showed proteinuria (n = 34) or < 90 mL/min/1.73 m2 of estimated glomerular filtration rate (eGFR) (n = 7), including 4 overlapping cases. Ninety-six patients (75%) had liver dysfunction (Forns index > 4.21). Patients with proteinuria received the Fontan procedure at an older age [78 (26-194) vs. 56 (8-292) months old, p = 0.02] and had a higher cardiac index [3.11 (1.49-6.35) vs. 2.71 (1.40-4.95) L/min/m2, p = 0.02], central venous pressure [12 (7-19) vs. 9 (5-19) mmHg, p < 0.001], and proportion with > 4.21 of Forns index (88% vs. 70%, p = 0.04) than those without proteinuria. The mean renal perfusion pressure was lower in patients with a reduced eGFR than those without it [55 (44-65) vs. 65 (45-102) mmHg, p = 0.03], but no other variables differed significantly. A multivariable analysis revealed that proteinuria was associated with an increased cardiac index (unit odds ratio 2.02, 95% confidence interval 1.12-3.65, p = 0.02). Seven patients with severe proteinuria had a lower oxygen saturation than those with no or mild proteinuria (p = 0.01, 0.03). Proteinuria or a decreased eGFR differentially occurred in approximately 30% of Fontan patients. Suboptimal Fontan circulation may contribute to the development of proteinuria and reduced eGFR.

Imaging of Fontan-Associated Liver Disease

ABSTRACT

The Fontan procedure is the definitive treatment for patients with single-ventricle physiology. Surgical advances have led to a growing number of patients surviving into adulthood. Fontan-associated liver disease (FALD) encompasses a spectrum of pathologic liver changes that occur secondary to altered physiology including congestion, fibrosis, and the development of liver masses. Assessment of FALD is difficult and relies on using imaging alongside of clinical, laboratory, and pathology information. Ultrasound, computed tomography, and magnetic resonance imaging are capable of demonstrating physiologic and hepatic parenchymal abnormalities commonly seen in FALD. Several novel imaging techniques including magnetic resonance elastography are under study for use as biomarkers for FALD progression. Imaging has a central role in detection and characterization of liver masses as benign or malignant. Benign FNH-like masses are commonly encountered; however, these can display atypical features and be mistaken for hepatocellular carcinoma (HCC). Fontan patients are at elevated risk for HCC, which is a feared complication and has a poor prognosis in this population. While imaging screening for HCC is widely advocated, no consensus has been reached regarding an optimal surveillance regimen.

The Fontan Udenafil Exercise Longitudinal Trial: Subgroup Analysis

The Pediatric Heart Network's Fontan Udenafil Exercise Longitudinal (FUEL) Trial (Mezzion Pharma Co. Ltd., NCT02741115) demonstrated improvements in some measures of exercise capacity and in the myocardial performance index following 6 months of treatment with udenafil (87.5 mg twice daily). In this post hoc analysis, we evaluate whether subgroups within the population experienced a differential effect on exercise performance in response to treatment. The effect of udenafil on exercise was evaluated within subgroups defined by baseline characteristics, including peak oxygen consumption (VO2), serum brain-type natriuretic peptide level, weight, race, gender, and ventricular morphology. Differences among subgroups were evaluated using ANCOVA modeling with fixed factors for treatment arm and subgroup and the interaction between treatment arm and subgroup. Within-subgroup analyses demonstrated trends toward quantitative improvements in peak VO2, work rate at the ventilatory anaerobic threshold (VAT), VO2 at VAT, and ventilatory efficiency (VE/VCO2) for those randomized to udenafil compared to placebo in nearly all subgroups. There was no identified differential response to udenafil based on baseline peak VO2, baseline BNP level, weight, race and ethnicity, gender, or ventricular morphology, although participants in the lowest tertile of baseline peak VO2 trended toward larger improvements. The absence of a differential response across subgroups in response to treatment with udenafil suggests that the treatment benefit may not be restricted to specific sub-populations. Further work is warranted to confirm the potential benefit of udenafil and to evaluate the long-term tolerability and safety of treatment and to determine the impact of udenafil on the development of other morbidities related to the Fontan circulation.Trial Registration NCT0274115.

EASL-ERN position paper on liver involvement in patients with Fontan-type circulation

Fontan-type surgery is the final step in the sequential palliative surgical treatment of infants born with a univentricular heart. The resulting long-term haemodynamic changes promote liver damage, leading to Fontan-associated liver disease (FALD), in virtually all patients with Fontan circulation. Owing to the lack of a uniform definition of FALD and the competitive risk of other complications developed by Fontan patients, the impact of FALD on the prognosis of these patients is currently debatable. However, based on the increasing number of adult Fontan patients and recent research interest, the European Association for The Study of the Liver and the European Reference Network on Rare Liver Diseases thought a position paper timely. The aims of the current paper are: (1) to provide a clear definition and description of FALD, including clinical, analytical, radiological, haemodynamic, and histological features; (2) to facilitate guidance for staging the liver disease; and (3) to provide evidence- and experience-based recommendations for the management of different clinical scenarios.

Liver Fibrosis Scores Are Associated With Resting and Exercise Fontan and Pulmonary Artery Wedge Pressures: Insights Into FALD

BACKGROUND

Alterations in liver perfusion and venous hypertension have been implicated in the pathophysiology of Fontan-associated liver disease (FALD). However, the correlation between exercise hemodynamics and markers of FALD have not been studied.

METHODS

We performed a retrospective review of 32 consecutive adults undergoing exercise catheterisation at the Mayo Clinic, Minnesota. Invasive hemodynamics were correlated with aspartate transaminase to platelet ratio index (APRI) and the Fibrosis-4 (Fib-4) score, well validated surrogates of liver fibrosis.

RESULTS

The mean age was 30.9 ± 7 years. The mean APRI was 0.5 ± 0.2 and the mean Fib-4 score 1.3 ± 0.8. Fib-4 scores correlated with spleen size on abdominal imaging (r = 0.40; P = 0.03). Resting Fontan pressure was 13.9 ± 3.9 mm Hg and pulmonary artery wedge pressure (PAWP) 10.0 ± 3.5 mm Hg. At peak exercise (69.4 ± 23.2 W), Fontan pressures increased to 26.5 ± 6.2 mm Hg and PAWP to 22.4 ± 7.1 mm Hg. APRI and Fib-4 score were directly related to Fontan pressure and PAWP at rest and during exercise, and inversely related to exercise arterial O2 saturation. Fib-4 inversely correlated with O2 delivery indices. Similarly, when categorising patients according to high APRI (> 0.5 vs ≤ 0.5) or Fib-4 score (≥ 1.45 vs < 1.45) according to previously proposed cutoffs for diagnosis of liver fibrosis, those with elevated scores had higher resting and exercise Fontan and PAWP pressure with lower O2 arterial saturation.

CONCLUSIONS

APRI and Fib-4 score correlated with resting and exercise Fontan pressure and PAWP. In addition, Fib-4 scores were inversely related to O2 delivery indices. These findings support a role played by hepatic venous hypertension and reduced O2 supply in patients with FALD.

Determinants of Advanced Liver Fibrosis in Adult Patients After Fontan Palliation: Usefulness of Ultrasound Transient Elastography

BACKGROUND

Fontan-associated liver disease is an increasing concern. Our aim was to assess prevalence and predictors of advanced liver fibrosis with a specific focus on utility of liver stiffness measurement by ultrasound transient elastography.

METHODS

A total of 97 adult Fontan patients (55% male, median age: 23.1 years, interquartile range [IQR]: 18.7-30.6); 92 (95%) were evaluated with transient elastography, and 50 (52%) underwent transjugular liver biopsy. Advanced liver fibrosis was defined as congestive hepatic fibrosis score 3 or 4.

RESULTS

Only 4 patients (4%) had liver stiffness values < 10 kilopascal (kPa). Liver-stiffness measurements correlated weakly with peak oxygen uptake on exercise testing and Fontan pressure but not with Model for End-Stage Liver Disease excluding INR (MELD-XI) score or spleen size. Serial follow-up liver stiffness measurements in 73 clinically stable patients showed large variability among individual patients. Advanced liver fibrosis was present in 35 of 50 (70%) patients on liver biopsy and was associated to MELD-XI-Score ≥ 11 and splenomegaly but not to liver-stiffness measurements. Advanced liver fibrosis was not associated with patient age or time since Fontan operation but with younger age at completion of Fontan (3.7 years, IQR: 2.3-6.3 vs 6.8 years; IQR: 3.5-12.1; P = 0.037).

CONCLUSIONS

In our cohort, advanced liver fibrosis was present in the majority of adult Fontan patients. Liver stiffness as measured by transient elastography was not associated with the degree of liver fibrosis. Because of its high variability on serial measurements, it seems not to be useful for clinical decision making. The unexpected finding that younger age at completion of Fontan was associated with advanced liver fibrosis merits further evaluation.