Hepatic Stiffness Using Shear Wave Elastography and the Related Factors for a Fontan Circulation

Prevalence, Risk Factors, and Prognosis for Fontan-Associated Liver Disease: A Systematic Review and Exploratory Meta-Analysis

BACKGROUND

Patients with Fontan circulation are at risk of progressive liver disease, but the prevalence and risk factors for Fontan-associated liver disease (FALD) remain unclear.

OBJECTIVES

The aim of the study was to review unbiased data on FALD prevalence, diagnostic methods, risk factors, and prognostic significance, and to undertake exploratory meta-analysis on available data.

METHODS

This systematic review included studies with unselected FALD screening. Outcomes were imaging or biopsy-proven cirrhosis, advanced fibrosis, portal hypertension, and hepatocellular carcinoma. Exploratory meta-analysis was performed, as well as subgroup analyses and meta-regression to explore contributors towards outcome heterogeneity.

RESULTS

Thirty-seven studies comprising 5,701 patients were included, with a median of 17 years of follow-up post-Fontan completion. All estimates of FALD were highly heterogeneous, reflecting variable patient factors and institutional practices. Cirrhosis was diagnosed in 21% of patients, but ranged from 0% to 76%. Advanced fibrosis without cirrhosis was noted in 30%, portal hypertension in 17%, and hepatocellular carcinoma in 2%, also with significant heterogeneity. Subgroup analysis and meta-regression highlighted several factors that contributed to such heterogeneity. It was found that cirrhosis was less commonly diagnosed by biopsy than by imaging (10% vs 26%). Other risk factors for cirrhosis included years post-Fontan completion, atriopulmonary Fontan, moderate or greater ventricular dysfunction, and higher pulmonary capillary wedge pressure. Qualitative synthesis noted FALD to be associated with elevated risk of cardiovascular and all-cause mortality.

CONCLUSIONS

Liver disease is common post-Fontan completion, though prevalence varies widely. Several risk factors should guide patient screening. A universal, prognostically meaningful FALD definition is needed to advance research and clinical care.

Clinical predictors and noninvasive imaging in Fontan-associated liver disease: A systematic review and meta-analysis

BACKGROUND

Despite the development of several imaging modalities for diagnosing Fontan-associated liver disease (FALD), there is no optimal protocol for the follow-up of FALD. We conducted a systematic review and meta-analysis to identify factors related to liver fibrosis using biopsy reports and to identify alternative noninvasive modalities that could better reflect liver histological changes in FALD.

METHODS

A systematic review and meta-analysis were conducted following the PRISMA guidelines Table S2. We searched Embase, PubMed, and Cochrane databases for studies on FALD, focusing on those assessing clinical factors associated with liver fibrosis severity through liver biopsy and noninvasive imaging techniques.

RESULTS

A total of 42 studies were identified, of which 12 conducted meta-analyses and subgroup analyses of the severity of liver fibrosis using liver biopsies. Liver biopsy results showed a weak positive correlation between Fontan duration and fibrosis severity (R = 0.36). Subgroup analyses revealed significant differences in hemodynamic parameters, such as Fontan pressure, between patients with mild and severe fibrosis. Platelet count, aspartate aminotransferase to platelet ratio index, and fibrosis-4 index were significantly associated with fibrosis severity, with severe fibrosis showing lower platelet counts and higher aspartate aminotransferase to platelet ratio index and fibrosis-4 index levels. Noninvasive imaging modalities, particularly magnetic resonance elastography and shear wave elastography, demonstrated strong correlations with biopsy-confirmed fibrosis severity.

CONCLUSIONS

This study identifies key clinical factors, and noninvasive modalities accurately reflect liver fibrosis severity in patients with FALD. Clinical factors such as platelet count, aspartate aminotransferase to platelet ratio index, and fibrosis-4 index may aid in identifying patients at risk for severe fibrosis. In addition, magnetic resonance elastography and shear wave elastography are promising tools for noninvasive assessment in our study. Further research is needed to refine these diagnostic approaches and improve patient management.

Shear-wave elastography for monitoring Fontan-associated liver disease: A prospective cohort study

The spectrum of Fontan-associated liver disease (FALD) varies from abnormal liver function tests to fibrosis and even cirrhosis. In this prospective study, we evaluated the role of shear-wave elastography (SWE) in predicting the presence of advanced FALD. Forty-eight patients (30 males, 13.9 [6-21] years) with a Fontan circulation were evaluated at 8.3 (2.1-18.7) years since the Fontan surgery. The median liver stiffness measurement (LSM) value was higher than values in normal children at 15.4 (9.5-38.7) kPa. The LSMs had a weak but significant correlation with age at the time of LSM (r = 0.25, p = 0.01) and duration post-Fontan surgery (r = 0.31, p = 0.02). It had a poor correlation with the concomitant aspartate transaminase-to-platelet ratio index (r = 0.1, p = 0.39). No difference in the elastography values between children with and without ultrasound evidence of advanced liver disease (17.7 [interquartile range, IQR: 4] vs. 16.1 [IQR: 6], p = 0.62] was observed. Further studies are required to determine the precise role of SWE as a noninvasive marker of liver fibrosis in FALD.

Mitochondrial dysfunction is associated with the severity of liver fibrosis in patients after the Fontan operation

The gold standard for determining the severity of liver disease in Fontan patients is now liver biopsy. Since it is an invasive procedure, this study determined the possibility of applying mitochondrial function from isolated peripheral blood mononuclear cells (PBMCs) as a non-invasive indicator of liver fibrosis. Fontan patients (n = 37) without known liver disease were analysed cross-sectionally. Patients were classified according to their histology using the METAVIR score as follows; F0/F1-no/mild fibrosis; F2-moderate fibrosis; and F3/F4-cirrhosis. Peripheral blood mononuclear cells were assessed for mitochondrial activity and apoptosis. This study did not find any significant differences in cardiac function among the groups according to liver histology. Interestingly, our findings indicated a significant decrease in maximal respiration and spare respiratory capacity, in both the moderate (F2) and cirrhosis (F3/F4) groups compared with the group without significant fibrosis (F0/F1). Moreover, the cirrhosis group exhibited higher levels of apoptosis and lower levels of live cells, compared with both the moderate and no significant fibrosis groups. In conclusion, the degree of liver fibrosis in Fontan patients is strongly correlated with mitochondrial dysfunction in PBMCs. Mitochondrial function and apoptosis could potentially serve as novel markers for tracking the progression of liver fibrosis in these patients.

Fontan Hepatopathy - Managing Unknowns

BACKGROUND AND AIMS

How to best monitor Fontan associated liver disease (FALD) remains unclear. We describe results from a prospective liver care pathway in adults (n=84) with a Fontan circulation.

METHODS

Routine assessment of the liver, by acoustic radiation force frequency and ultrasound was undertaken. Results, including liver biochemistry, systemic ventricular function (echocardiography), functional class, medication use and clinical endpoints (varices, hepatocellular carcinoma, heart transplantation and death) were collated.

RESULTS

Most individuals returned a cirrhotic range acoustic radiation force impulse imaging (ARFI) result. ARFI values were greater in the proportion of individuals with hepatic nodularity (p=0.024). Univariate analysis demonstrated moderate correlation with platelet number (Spearmans rho= -0.376, p=0.049). Patients with clinical endpoints had lower platelets (p=0.012) but only a trend to hepatic nodularity (p=0.057). Clinical endpoints were more common in those with ventricular dysfunction (p=0.011). Multivariate analysis revealed that age at Fontan and being on angiotensin converting enzyme inhibitors (ACEI) predicted ARFI score (β=0.06 (95% CI 0.01-0.09), p=0.007 and β=0.53 (95% CI 0.17-0.89), p=0.005, respectively). However, these associations were not significant once adjusted for Fontan type, age at ARFI, systemic ventricle morphology, ventricle function, or Model for End-stage Liver Disease (MELD-XI) excluding international normalised ratio (INR) (p>0.05 for all).

CONCLUSIONS

Ideal FALD monitoring remains unclear. ARFI has utility as a binary non-invasive indicator of cirrhosis, highlighting individuals who may need more frequent ongoing monitoring for hepatocellular carcinoma. However, no definite advantage to serial ARFI, once cirrhotic range ARFI results are present, has been identified.

Liver nodules after the Fontan operation: role of the computerised tomography scan

Currently, there is an increasing prevalence of liver nodules in patients following the Fontan operation. The appropriate non-invasive modalities have been applied to assess a diagnosis of Fontan-associated liver disease. The aims of this study were to determine the prevalence and associated factors for the presence of liver nodules using CT scan. A cross-sectional study of 34 patients older than 15 years of age was recruited. Ultrasound upper abdomen, ultrasound liver elastography, and CT scan of the upper abdomen were performed after the Fontan operation. The median age of patients was 20 years (range 14-36 years). The median age at the Fontan operation was 7 years (range 5-17 years) and the duration after the Fontan operation was 12 years (range 4-22 years). The prevalence of liver nodules was 62% as detected by CT scans. Hepatic vein pressure in patients with liver nodules was significantly higher than in those without liver nodules. Hepatic vein pressure above 13 mmHg was a factor associated with liver nodules. There was little agreement between the ultrasound of the upper abdomen and CT scan of the upper abdomen in the evaluation of liver nodules. Hepatic pressure was the only associated factor for the occurrence of liver nodules in patients following the Fontan operation. The prevalence of liver nodules was very high after the Fontan operation. The upper abdomen CT scan should be performed for the surveillance of liver nodules in every Fontan patient over the age of 15 years.

Elastography for Pediatric Chronic Liver Disease: A Review and Expert Opinion

In adults with chronic liver diseases, ultrasound and magnetic resonance shear wave elastography (SWE) can replace liver biopsy in several clinical scenarios. Several guidelines on the use of ultrasound SWE for the adult population have been published. However, the number of publications in the pediatric population is limited, and available guidelines on SWE do not specifically address pediatric chronic liver diseases. In this article, we review the literature on the use of SWE for pediatric chronic liver diseases and provide expert opinion on how to use SWE, both ultrasound and magnetic resonance techniques, in the pediatric population.

Quantification of Hepatic and Splenic Stiffness After Fontan Procedure in Children and Clinical Implications

We aimed to investigate Fontan associated liver disease in children by shear wave elastography (SWE). This is a single-center, prospective case-control study included 41 patients with Fontan physiology and 30 healthy controls. Hepatic and splenic shear wave elasticity values were exhibited both as kPa and m/s. The mean hepatic SWE values of Fontan patients (n = 41; 15.8 ± 3.2 kPa or 2.5 ± 1.8 m/s) were significantly higher than the control group (n = 30; 5.59 ± 0.6 kPa or 1.37 ± 0.07 m/s) (P < 0.001). The mean splenic SWE values of Fontan patients were (25.6 ± 4.61 kPa or 2.85 ± 0.22 m/s) significantly higher than the control group (15.9 ± 1.44 kPa or 2.29 ± 0.1 m/s) (P < 0.001). There were statistically significant positive correlations among the follow-up duration after the Fontan procedure with NT-proBNP (P = 0.008, r = 1) and prothrombin time (P = 0.009, r = 0.4) as well as the hepatic SWE values with alanine aminotransferase (P = 0.039, r = 0.32), gamma-glutamyl transferase (P = 0.045, r = 0.31), and PT (P = 0.011, r = 0.39). There has been statistically significant moderate positive correlations of splenic stiffness values with PT (P = 0.047, r = 0.34), and INR (P = 0.038, r = 0.35). The sensitivity and specificity of liver stiffness cutoff value as 11.1 kPa for detection of Fontan associated liver disease were 95% and 100%, respectively. The hepatic and splenic stiffness increase independently in Fontan patients due to parenchymal disease. Hepatic SWE is a reliable and noninvasive predictor of early hepatic alterations that could not be detected only by biochemical results or routine ultrasound examinations.

Imaging of Fontan-associated liver disease

The Fontan operation has dramatically altered the natural history of functionally single ventricle congenital heart disease. Patients who have undergone the Fontan operation are living longer and, thus, noncardiac morbidity resulting from the Fontan operation is increasingly being recognized. Fontan-associated liver disease (FALD), one of the chief morbidities following the Fontan operation, is believed to be a multifactorial process that manifests as hepatic congestion and fibrosis, portal hypertension, and development of focal liver lesions, including malignant tumors. This article reviews the imaging findings of FALD in the pediatric and young adult population, reviews the literature related to the imaging of FALD and discusses possible screening algorithms for this population. The need for further research to better understand the causes of FALD, to establish if early liver stiffness measurements (or their change over time) predict long-term outcomes and complications, and to define optimal liver screening procedures is highlighted.

Noninvasive Assessment of Liver Stiffness in Patients Undergoing the Fontan Procedure

BACKGROUND

Hepatic derangements and liver injury following the Fontan operation (FO) may progress in some cases to hepatic fibrosis (HF) and cirrhosis. The respective roles of transient elastography (TE) or FibroScan, shear wave elastography (SWE), and aspartate transaminase to platelet ratio index (APRI) in assessing liver stiffness (LS) and possible liver injury in these patients are unclear.

METHODS

Thirty-nine patients (31 males), mean age 11.8 ± 5.7 years, median 11 years (interquartile range: 7-14.7 years), undergoing the FO between November 2017 and December 2018 were included. Liver stiffness and HF assessment was done with TE, SWE, and APRI in the preoperative period and postoperatively at 3-, 6-, and 12-month interval.

RESULTS

The LS values increased over time (postoperative values at 3, 6, and 12 months) as compared to preoperative values by both FibroScan and SWE. The change in liver stiffness measurement (LSM) was statistically significant: LSM0 to LSM3 (P ≤ .0001), LSM0 to LSM6 (P ≤ .0001), and LSM0 to LSM12 (P = .001). Similarly, significant changes were observed on SWE: SWE0 to SWE3 (P ≤ .0001), SWE0 to SWE6 (P ≤ .0001), and SWE0 to SWE12 (P = .001). There was no significant change in the APRI values over time.

CONCLUSION

Noninvasive methods such as FibroScan and SWE may be of use to assess LS in follow-up of patients undergoing the FO for early recognition of hepatic changes.

Viscoelastic Biomarkers of Ex Vivo Liver Samples via Torsional Wave Elastography

The clinical ultrasound community demands mechanisms to obtain the viscoelastic biomarkers of soft tissue in order to quantify the tissue condition and to be able to track its consistency. Torsional Wave Elastography (TWE) is an emerging technique proposed for interrogating soft tissue mechanical viscoelastic constants. Torsional waves are a particular configuration of shear waves, which propagate asymmetrically in-depth and are radially transmitted by a disc and received by a ring. This configuration is shown to be particularly efficient in minimizing spurious p-waves components and is sensitive to mechanical constants, especially in cylinder-shaped organs. The objective of this work was to validate (TWE) technique against Shear Wave Elasticity Imaging (SWEI) technique through the determination of shear wave velocity, shear moduli, and viscosity of ex vivo chicken liver samples and tissue mimicking hydrogel phantoms. The results of shear moduli for ex vivo liver tissue vary 1.69–4.0kPa using TWE technique and 1.32–4.48kPa using SWEI technique for a range of frequencies from 200 to 800Hz. Kelvin–Voigt viscoelastic parameters reported values of μ = 1.51kPa and η = 0.54Pa·s using TWE and μ = 1.02kPa and η = 0.63Pa·s using SWEI. Preliminary results show that the proposed technique successfully allows reconstructing shear wave velocity, shear moduli, and viscosity mechanical biomarkers from the propagated torsional wave, establishing a proof of principle and warranting further studies.

Non-invasive Quantitative Assessment of Muscle Force Based on Ultrasonic Shear Wave Elastography

The objective of this study was to investigate the feasibility of using shear wave elastography (SWE) to indirectly measure passive muscle force and to examine the effects of muscle mass and scan angle. We measured the Young's moduli of 24 specimens from six muscles of four swine at different passive muscle loads under different scan angles (0°, 30°, 60° and 90°) using SWE. Highly linear relationships between Young's modulus E and passive muscle force F were found for all 24 muscle specimens at 0^o scan angle with coefficients of determination R² ranging from 0.984 to 0.999. The results indicate that the muscle mass has no significant effect on the muscle E-F relationship, whereas E-F linearity decreases disproportionately with increased scan angle. These findings suggest that SWE, when carefully applied, can provide a highly reliable tool to measure muscle Young's modulus, and could be used to assess the muscle force quantitatively.