Diminished liver microperfusion in Fontan patients: A biexponential DWI study

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 parenchymal changes and association with cardiac magnetic resonance imaging findings in repaired tetralogy of Fallot: an intravoxel incoherent motion magnetic resonance imaging study

BACKGROUND

Liver disease can develop in repaired tetralogy of Fallot (TOF) from hepatic congestion caused by volume and pressure overload of the right ventricle. Noninvasive assessment of the liver is important for diagnosing and managing children with TOF.

OBJECTIVE

To evaluate subclinical hepatic changes without liver function test abnormality in adolescents with repaired TOF using intravoxel incoherent motion (IVIM) MRI and cardiac MRI findings.

MATERIALS AND METHODS

We included 106 young adults (75 with repaired TOF and 31 healthy individuals) in the study. Liver IVIM MRI examinations were performed with 10 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800 s/mm²). Two observers measured IVIM MRI parameters D true, D* and f, as well as apparent diffusion coefficient (ADC) values in liver segments 5-8.

RESULTS

D* and f values were significantly lower in adolescents with TOF (P = 0.003 vs. P = 0.05, respectively). ADC values were higher in adolescents with TOF (P = 0.005). However, we found no significant difference between adolescents with and without TOF in terms of Dtrue (P = 0.53). There was a significant correlation between f value and right ventricular ejection fraction. The intraclass correlation coefficient (ICC) analysis of the two observers showed substantial-to-excellent agreement for D, f, D true and ADC (0.7, 0.8, 0.9 and 0.8, respectively).

CONCLUSION

The results of our study suggest that impaired microperfusion with increased ADC values in adolescents with repaired TOF reflect hepatic congestion rather than fibrosis. Hepatic congestion characterized by decreased ADC values can be easily differentiated before fibrotic changes occur by using IVIM MRI to assess diffusion and microcapillary perfusion separately.

Non-contrast enhanced magnetic resonance imaging for characterization of Fontan associated liver disease

OBJECTIVES

To evaluate the ability of non-contrast enhanced magnetic resonance imaging (MRI) techniques to characterize Fontan associated liver disease (FALD) in adolescent and adult Fontan patients.

METHODS

Fontan patients (n = 29) and healthy controls (n = 13) underwent an MRI protocol with T₁, T₂ and Apparent Diffusion Coefficient (ADC) mapping. Routine FALD screening included abdominal ultrasound and laboratory testing.

RESULTS

Median follow-up after Fontan operation was 15.1 (IQR 12.0-16.8) years. Distinct differences in tissue characteristics were visualized. T₁ and T₂ relaxation times were prolonged in Fontan patients, particularly of the right lobe (T₁: 745 (IQR 715-784) ms vs. 586 (IQR 555-602) ms, p < 0.001; T₂: 63 (IQR 59-64) ms vs. 58 (IQR 56-60) ms, p = 0.002). Left lobe ADC was lower in Fontan patients (1.10 (IQR 1.06-1.18) x 10^-3 mm²/s vs. 1.23 (IQR 1.19-1.29) x 10^-3 mm²/s, p < 0.001). T₂ mapping was able to differentiate between controls and Fontan patients with different FALD severity. Right lobe T₂ was higher in patients with moderate or severe in comparison to those with no or mild changes and healthy controls (64 (IQR 61-67) ms vs. 60 (IQR 59-63) ms vs. 58 (IQR 56-60) ms, p = 0.001).

CONCLUSIONS

Non-contrast enhanced MRI methods are able to visualize regional differences in liver tissue characteristics. T₁ and T₂ relaxation times were prolonged in Fontan patients suggestive of fibrosis or congestive hepatopathy, while reduced ADC might reflect impaired microperfusion. These methods have promising clinical potential for detection of liver abnormalities in Fontan patients. The usefulness of T₂ mapping to grade FALD severity merits further investigation.

GDF-15 (Growth Differentiation Factor 15) Is Associated With Hospitalization and Mortality in Patients With a Fontan Circulation

Background We investigated serial serum levels of GDF-15 (growth differentiation factor 15) in Fontan patients and their relation to outcome. Methods and Results In this single-center prospective study of consecutive Fontan patients, serial serum GDF-15 measurement and clinical assessment was done at baseline (n=81) and after 2 years (n=51). The association between GDF-15 and the combined end point of all-cause mortality, heart transplant listing, and Fontan-related hospitalization was investigated. Median age at baseline was 21 years (interquartile range: 15-28 years). Median GDF-15 serum levels at baseline were 552 pg/mL (interquartile range: 453-729 pg/mL). GDF-15 serum levels correlated positively with age, age at Fontan initiation, New York Heart Association class, and serum levels of NT-proBNP (N-terminal pro-B-type natriuretic peptide) and ɣGT (γ-glutamyltransferase) and negatively with exercise capacity. During a median follow-up of 4.8 years (interquartile range: 3.3-5.5 years), the combined end point occurred in 30 patients (37%). Multivariate Cox regression showed that patients with the highest baseline GDF-15 (n=20, defined as the upper quartile) had a higher risk of hospitalization or death than the lowest 3 quartiles (hazard ratio [HR], 2.76; 95% CI, 1.27-6.00; P=0.011). After 2 years of follow-up, patients in whom serum level of GDF-15 increased to >70 pg/mL (n=13) had a higher risk of hospitalization or death than the lowest 3 quartiles (HR, 2.69; 95% CI, 1.03-6.99; P=0.043). Conclusions In Fontan patients, elevated serum levels of GDF-15 are associated with worse functional status and predict Fontan-related events. Furthermore, serial measurements showed that an increase in GDF-15 serum level was associated with increased risk for adverse outcome.

Intravoxel incoherent motion imaging has the possibility to detect liver abnormalities in young Fontan patients with good hemodynamics

INTRODUCTION

Liver fibrosis and cirrhosis are one of the critical complications in Fontan patients. However, there are no well-established non-invasive and quantitative techniques for evaluating liver abnormalities in Fontan patients. Intravoxel incoherent motion diffusion-weighted imaging with MRI is a non-invasive and quantitative method to evaluate capillary network perfusion and molecular diffusion. The objective of this study is to assess the feasibility of intravoxel incoherent motion imaging in evaluating liver abnormalities in Fontan children.

MATERIALS AND METHODS

Five consecutive Fontan patients and four age-matched healthy volunteers were included. Fontan patients were 12.8 ± 1.5 years old at the time of MRI scan. Intravoxel incoherent motion imaging parameters (D, D*, and f values) within the right hepatic lobe were compared. Laboratory test, ultrasonography, and cardiac MRI were also conducted in the Fontan patients. Results of cardiac catheterization conducted within one year of the intravoxel incoherent motion imaging were also examined.

RESULTS

In Fontan patients, laboratory test and liver ultrasonography showed almost normal liver condition. Cardiac catheter and MRI showed good Fontan circulation. Cardiac index was 2.61 ± 0.23 L/min/m2. Intravoxel incoherent motion imaging parameters D, D*, and f values were lower in Fontan patients compared with controls (D: 1.1 ± 0.0 versus 1.3 ± 0.2 × 10-3 mm2/second (p = 0.04), D*: 30.8 ± 24.8 versus 113.2 ± 25.6 × 10-3 mm2/second (p < 0.01), and f: 13.2 ± 3.1 versus 22.4 ± 2.4% (p < 0.01), respectively).

CONCLUSIONS

Intravoxel incoherent motion imaging is feasible for evaluating liver abnormalities in children with Fontan circulation.

Dependence of intravoxel incoherent motion diffusion MR threshold b-value selection for separating perfusion and diffusion compartments and liver fibrosis diagnostic performance

BACKGROUND

Intravoxel incoherent motion (IVIM) tissue parameters depend on the threshold b-value.

PURPOSE

To explore how threshold b-value impacts PF ( f), D_slow ( D), and D_fast ( D*) values and their performance for liver fibrosis detection.

MATERIAL AND METHODS

Fifteen healthy volunteers and 33 hepatitis B patients were included. With a 1.5-T magnetic resonance (MR) scanner and respiration gating, IVIM data were acquired with ten b-values of 10, 20, 40, 60, 80, 100, 150, 200, 400, and 800 s/mm². Signal measurement was performed on the right liver. Segmented-unconstrained analysis was used to compute IVIM parameters and six threshold b-values in the range of 40-200 s/mm² were compared. PF, D_slow, and D_fast values were placed along the x-axis, y-axis, and z-axis, and a plane was defined to separate volunteers from patients.

RESULTS

Higher threshold b-values were associated with higher PF measurement; while lower threshold b-values led to higher D_slow and D_fast measurements. The dependence of PF, D_slow, and D_fast on threshold b-value differed between healthy livers and fibrotic livers; with the healthy livers showing a higher dependence. Threshold b-value = 60 s/mm² showed the largest mean distance between healthy liver datapoints vs. fibrotic liver datapoints, and a classification and regression tree showed that a combination of PF (PF < 9.5%), D_slow (D_slow < 1.239 × 10^-3 mm²/s), and D_fast (D_fast < 20.85 × 10^-3 mm²/s) differentiated healthy individuals and all individual fibrotic livers with an area under the curve of logistic regression (AUC) of 1.

CONCLUSION

For segmented-unconstrained analysis, the selection of threshold b-value = 60 s/mm² improves IVIM differentiation between healthy livers and fibrotic livers.

Current spectrum, challenges and new developments in the surgical care of adults with congenital heart disease

Today, more than two thirds of patients with congenital heart disease (CHD) are adults. Cardiac surgery plays an essential role in restoring and maintaining cardiac function, aside from evolving medical treatment and catheter-based interventions. The aim of the present publication was to describe the spectrum of operations performed on adults with CHD (ACHD) by reviewing current literature. Currently, surgery for ACHD is predominantly valve surgery, since valvular pathologies are often either a part of the basic heart defect or develop as sequelae of corrective or palliative surgery. Surgical techniques for valve repair, established in patients with acquired heart disease (non-ACHD), can often be transferred to ACHD. New valve substitutes may help to reduce the number of redo operations. Most of valve operations yield good results in terms of survival and quality of life, with the precondition that the ventricular function is preserved. Heart failure due to end-stage CHD is the most frequent cause of mortality in ACHD. However, surgical treatment by means of mechanical circulatory support (MCS) is still uncommon and the mortality exceeds the one following other operations in ACHD. Currently, different devices are used and new technical developments are in progress. However, there still is no ideal assist device available. Therefore, heart transplantation remains the only valid option for end-stage CHD. Despite higher early mortality following heart transplantation in ACHD compared to non-ACHD, the long-term survival compares favorably to non-ACHD. There is room for improvement by refining the indications, the time of listing, and the perioperative care of ACHD transplant patients. Sudden death is the second most frequent cause of mortality in ACHD. Ventricular tachycardia is the most frequent cause of sudden death followed by coronary artery anomaly. Due to the increasing awareness of physicians and the improved imaging techniques, coronary artery anomalies are coming more into the focus of cardiac surgeons. However, the reported experience is limited and it is currently difficult to provide a standardized and generally applicable recommendation for the indication and the adequate surgical technique. With the increasing age and complexity of ACHD, treatment of rhythm disturbances by surgical ablation, pacemaker or implantable cardioverter defibrillator (ICD) implantation and resynchronisation gains importance. A risk score specifically designed for surgery in ACHD is among the newest developments in predicting the outcome of surgical treatment of ACHD. This evidence-based score, derived from and validated with data from the Society of Thoracic Surgeons Congenital Heart Surgery Database, enables comparison of risk-adjusted performance of the whole spectrum of procedures performed in ACHD and helps in understanding the differences in surgical outcomes. The score is thus a powerful tool for quality control and quality improvement. In conclusion, new developments in surgery for ACHD are currently made with regard to valve surgery, which comprises more than half of all operations in ACHD and in treatment of end-stage CHD, which still yields high mortality and morbidity.

Assessment of Advanced Liver Fibrosis and the Risk for Hepatic Decompensation in Patients With Congestive Hepatopathy

Congestive hepatopathy (CH) arises from chronically elevated right-sided heart pressures transmitted to the liver by passive venous congestion. Over time, CH can lead to hepatic bridging fibrosis, decompensated cirrhosis, and hepatocellular carcinoma. Currently, there are no evidence-based guidelines to direct appropriate screening or management of patients with CH, partly because of the inability of current clinical tools (serum tests, imaging studies, liver stiffness measurements, and liver biopsy) to accurately estimate hepatic fibrosis or the risk for hepatic decompensation. The Model for End-Stage Liver Disease excluding international normalized ratio (MELD-XI) score is the only validated serum-based test to predict clinical outcomes in CH. Noninvasive liver stiffness measurements are proving to be of minimal utility as all patients with CH have elevated values that currently cannot differentiate between congestion and fibrosis. In addition, fibrosis staging by liver biopsy is difficult to standardize because of heterogeneous collagen deposition in CH. Moreover, liver biopsy results have little predictive value for post-heart transplant hepatic outcomes in patients with CH. Evaluating liver nodules and masses is also complicated in CH as the finding of delayed venous washout in nodules is not specific for hepatocellular carcinoma in the background of a congested liver, and these lesions may require biopsy to confirm the diagnosis. The lack of effective clinical tools for predicting liver fibrosis and liver function suggests the need for the development of novel biomarkers in patients with CH to assist in the management of this complicated disease. (Hepatology 2018; 00:000-000).

Liver intravoxel incoherent motion diffusion-weighted imaging for the assessment of hepatic steatosis and fibrosis in children

AIM

To evaluate the correlation between intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters and the degree of hepatic steatosis and fibrosis in children.

METHODS

This retrospective study was approved by the institutional review board. The children (≤ 18 years) who underwent liver IVIM DWI with 8 b-values under the suspicion of hepatic steatosis or fibrosis from February 2013 to November 2016 were included. Subjects were divided into normal, fatty liver (FAT), and fibrotic liver (FIB) groups. The slow diffusion coefficient (D), fast diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADC) were measured. MR proton density fat fraction (PDFF), MR elastography (MRE), and IVIM values were compared.

RESULTS

A total of 123 children (median age of 12 years old, range: 6-18 years) were included, with 8 in the normal group, 93 in the FAT group, and 22 in the FIB group. The D* values were lower in the FIB group compared with those of the normal (P = 0.015) and FAT (P = 0.003) groups. The f values were lower in the FIB group compared with the FAT group (P = 0.001). In multivariate analyses, PDFF value was positively correlated with f value (β = 3.194, P < 0.001), and MRE value was negatively correlated with D* value (β = -7.031, P = 0.032). The D and ADC values were not influenced by PDFF or MRE value.

CONCLUSION

In liver IVIM DWI with multiple b-values in children, there was a positive correlation between hepatic fat and blood volume, and a negative correlation between hepatic stiffness and endovascular blood flow velocity, while diffusion-related parameters were not affected.