LIVER STIFFNESS EVALUATION USING ACOUSTIC RADIATION FORCE IMPULSE ELASTOGRAPHY IN PEDIATRIC AND ADULT PATIENTS WITH CONGENITAL HEART DISEASE

Background: Hepatic complications are common in patients with congenital heart disease as a consequence of the primary cardiac defect or as a result of surgical palliation (e.g. Fontan procedure). Liver involvement represents a significant challenge and an adequate hepatic surveillance is fundamental. Liver biopsy represents the gold standard for diagnosis and staging of hepatic fibrosis but it’s an invasive procedure not suitable for a routine setting. Acoustic radiation force impulse (ARFI) elastography is a recently developed technique that allows to assess hepatic stiffness in a non-invasive and reproducible way. The usefulness of ARFI imaging has been described in adult Fontan patients but only few studies have been reported in the pediatric Fontan population and no one in CHD others than Fontan. Aim: The aims of this study were to assess liver stiffness, using ElastPQTM acoustic radiation force impulse elastography, in pediatric and adult patients with CHD, to compare liver stiffness values with healthy controls and to analyze possible associations between ARFI values and clinical, biochemical, cardiac and hepatic parameters. Materials and methods: Pediatric and adult patients that underwent heart surgery for CHD and were followed at the Cardiology Unit of the “Azienda Ospedaliera Universitaria Integrata” of Verona between October 2018 and October 2020 were prospectively enrolled. Controls subjects without any liver or cardiac disease matched for age and sex to the case group were also included. The latest laboratory tests and echocardiogram available were collected. Liver ultrasound and ARFI measurement of liver stiffness were performed by a specifically trained single expert radiologist using the Philips Healtcare® ultrasound with ElastPQTM software. Results: A total of 50 subjects were enrolled for the study: 20 Fontan patients (13 males, median age at ARFI 8.4 years), 13 non-Fontan (9 males, median age at ARFI 4.8 years) and 17 controls (6 males, median age at ARFI 10 years). The median values of ARFI elastography were significantly higher in patients with CHDs (Fontan and non-Fontan patients) compared to control subjects (p<0.01). Patients with morphological right ventricle overload showed significantly higher results (p=0.02). The cut-off of 5.7 kPa at elastography was used to discriminate between normal liver and liver with signs of congestion or fibrosis. All controls subjects showed ARFI values <5.7 kPa whereas only 25% of Fontan patients and 46% of non-Fontan were below that threshold. Liver stiffness values were positively correlated with time from surgery and age at liver evaluation (p<0.01). The number of platelets and white blood cells were inversely related to liver stiffness measurements (p=0.04 and p=0.05 respectively). The AST to platelet ratio index positively correlated with ARFI elastography results (p<0.03). No significant correlations between ARFI results and other biochemical or cardiac parameters were found. Conclusions: Our data showed that the median values of liver stiffness measured with ElastPQTM pSWE were significantly higher in patients with CHDs compared to control subjects and, in particular, in those with morphological right ventricle overload. Liver stiffness values were also correlated with time from surgery and age at liver evaluation. The number of platelets and white blood cells were inversely related to liver stiffness measurements supporting the need of a screening for portal hypertension and splenomegaly in these patients. The AST to platelet ratio index was also correlated to ARFI elastography results suggesting that liver stiffness may reflect the evolution of liver fibrosis. In conclusion, our study demonstrated, for the first time in literature, that acoustic radiation force impulse elastography (pSWE) with ElastPQTM software can be a useful tool to assess liver stiffness in patients with Fontan circulation and other congenital heart disease.