Ultrasound Shear Wave Elastography as a Measure of Porcine Hepatic Disease in Right Heart Dysfunction: A Pilot Study

Pulmonary artery banding in sheep: a novel large animal model for congestive hepatopathy

Congestive hepatopathy is becoming increasingly recognized among Fontan-palliated patients. Elevated central venous pressure is thought to drive the pathologic progression, characterized by sinusoidal dilatation, congestion, and fibrosis. A clinically relevant large animal model for congestive hepatopathy would provide a valuable platform for researching novel biomarkers, treatment, and prevention. Here, we report on a titratable, sheep pulmonary artery banding model for this disease application. Pulmonary artery banding was achieved by progressively inflating the implanted pulmonary artery cuff. Right ventricular catheter was implanted to draw venous blood samples and measure pressure. The pulmonary artery cuff pressure served as a surrogate for the intensity of pulmonary artery banding and was measured weekly. After about 9 wk, animals were euthanized, and the liver was harvested for histopathological assessment. Nine animal subjects received pulmonary artery banding for 64 ± 8 days. Four of the nine subjects exhibited moderate to severe liver injury, and three of those four exhibited bridging fibrosis. Increasing pulmonary artery cuff pressure significantly correlated with declining mixed venous oxygen saturation (P = 3.29 × 10-5), and higher congestive hepatic fibrosis score (P = 0.0238), suggesting that pulmonary artery banding strategy can be titrated to achieve right-sided congestion and liver fibrosis. Blood analyses demonstrated an increase in plasma bile acids, aspartate aminotransferase, and γ-glutamyltransferase among subjects with moderate to severe injury, further corroborating liver tissue findings. Our large animal pulmonary artery banding model recapitulates congestive hepatopathy and provides a basis to bridge the current gaps in scientific and clinical understanding about the disease.NEW & NOTEWORTHY We present here a large animal platform for congestive hepatopathy, a disease growing in clinical prevalence due to the increasing number of Fontan-palliated patients. Further data are needed to develop a better clinical management strategy for this poorly characterized patient population. Previous reports of animal models to study this disease have mostly been in small animals with limited fidelity. We show that congestive hepatopathy can be replicated in a chronic, progressive pulmonary artery banding model in sheep. We also show that the banding strategy can be controlled to titrate the level of liver injury. To date, we do not know of any other large animal model that can achieve this level of control over disease phenotype and clinical relevance.

Noninvasive ultrasound technique for assessment of liver fibrosis and cardiac function in Fontan-associated liver disease: diagnosis based on elastography and hepatic vein waveform type

PURPOSE

Patients with a Fontan circulation tend to develop liver fibrosis, liver cirrhosis and even hepatocellular carcinoma. A noninvasive ultrasound technique for liver fibrosis and cardiac function assessment in Fontan-associated liver disease (FALD) is needed to evaluate disease progression in real time. This study aimed to evaluate whether hepatic vein (HV) waveform analysis and elastography could be alternative markers to cardiac index (CI) in patients with FALD and assess factors influencing elastography measurements in FALD cases.

METHODS

All patients underwent cardiac catheterization, B-mode ultrasound and ultrasound elastography measurement. Moreover, we measured serum markers related to fibrosis and examined HV blood flow using duplex Doppler ultrasonography.

RESULTS

Forty-three patients (median age, 17 years; interquartile range, 12-25 years; 29 men, 6 with liver biopsy) were enrolled. The real-time tissue elastography (RTE) value was significantly higher in patients who underwent surgery > 7 years prior, suggesting that this value probably reflects the liver fibrosis due to FALD from the early fibrosis stage. The ultrasound elastography did not significantly correlate with hemodynamic parameters. The area under the receiver operating curve for the diagnosis of CI < 2.2 L/min/m² using HV waveform was superior to the results from elastography and calculated fibrosis indices.

CONCLUSION

HV waveform can be used as a noninvasive measurable surrogate marker for CI. The RTE value increased overtime after the operation and would reflect liver fibrosis. The combination of RTE and HV waveform type could be useful noninvasive tools to evaluate clinical conditions in FALD patients in real time.

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.

Attenuation Measuring Ultrasound Shearwave Elastography as a Method for Evaluating Pancreatic Viscoelasticity

Pancreatic cancer is the fourth most common cause of cancer-related fatalities as there are a limited number of tools to diagnose this disease in its early stages. Pancreatitis is characterized as an inflammation of the pancreatic tissue due to an excess amount of pancreatic enzymes remaining in the organ. Both of these diseases result in a stiffening of the tissue which makes them suitable for the use of elastography techniques as a diagnostic method. However, these methods typically assume that the tissue is purely elastic when biological tissue is inherently viscoelastic. The attenuation measuring ultrasound shear elastography (AMUSE) method, which measures both attenuation and shear wave velocity was used to characterize the viscoelasticity of pancreatic tissue. This method was tested in ex vivo normal porcine samples that were also stiffened in formalin and in vivo by conducting studies in healthy human subjects. Ex vivo testing showed ranges of phase velocity, group velocity, and phase attenuation values of 1.05 - 1.33 m/s, 0.83 - 1.12 m/s, and 183 - 210 Np/m. After immersing the ex vivo tissue in formalin there was a distinguishable difference between normal and stiffened tissue. This study produced percent difference ranges of phase velocity, group velocity, and phase attenuation from 0 to 100 minutes in formalin of 30.0% - 56.5%, 38.2% - 58.6%, and 55.8% - 64.8%, respectively. The ranges of phase velocity, group velocity, and phase attenuation results in human subjects were 1.53 - 1.60 m/s, 1.76 - 1.91 m/s, and 196 - 204 Np/m, respectively. These results were within a similar range reported by other elastography techniques. Further work with the AMUSE method in subjects with pancreatitis and cancer is needed to determine its effectiveness in showing a difference between healthy and diseased tissue in humans.

Evaluation and Management of the Child and Adult With Fontan Circulation: A Scientific Statement From the American Heart Association

It has been 50 years since Francis Fontan pioneered the operation that today bears his name. Initially designed for patients with tricuspid atresia, this procedure is now offered for a vast array of congenital cardiac lesions when a circulation with 2 ventricles cannot be achieved. As a result of technical advances and improvements in patient selection and perioperative management, survival has steadily increased, and it is estimated that patients operated on today may hope for a 30-year survival of >80%. Up to 70 000 patients may be alive worldwide today with Fontan circulation, and this population is expected to double in the next 20 years. In the absence of a subpulmonary ventricle, Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output. The addition of this acquired abnormal circulation to innate abnormalities associated with single-ventricle congenital heart disease exposes these patients to a variety of complications. Circulatory failure, ventricular dysfunction, atrioventricular valve regurgitation, arrhythmia, protein-losing enteropathy, and plastic bronchitis are potential complications of the Fontan circulation. Abnormalities in body composition, bone structure, and growth have been detected. Liver fibrosis and renal dysfunction are common and may progress over time. Cognitive, neuropsychological, and behavioral deficits are highly prevalent. As a testimony to the success of the current strategy of care, the proportion of adults with Fontan circulation is increasing. Healthcare providers are ill-prepared to tackle these challenges, as well as specific needs such as contraception and pregnancy in female patients. The role of therapies such as cardiovascular drugs to prevent and treat complications, heart transplantation, and mechanical circulatory support remains undetermined. There is a clear need for consensus on how best to follow up patients with Fontan circulation and to treat their complications. This American Heart Association statement summarizes the current state of knowledge on the Fontan circulation and its consequences. A proposed surveillance testing toolkit provides recommendations for a range of acceptable approaches to follow-up care for the patient with Fontan circulation. Gaps in knowledge and areas for future focus of investigation are highlighted, with the objective of laying the groundwork for creating a normal quality and duration of life for these unique individuals.