Liver stiffness modifications shortly after total cavopulmonary connection

Hepatic damage in Fontan circulation setting is well known. Mainly represented by fibrosis, it is still poorly understood. Transient hepatic elastography (Fibro-Scan) is a useful tool to test liver stiffness and is commonly used in the evaluation of liver fibrosis. Unfortunately, the increase of inferior vena cava pressure consequent to total cavopulmonary connection can probably interfere with Fibro-Scan evaluation altering the result evaluation with the conventional scale. To verify this hypothesis and to quantify the impact of venous pressure on Fibro-Scan results, we checked perioperative liver stiffness changes in patients undergoing total cavopulmonary connection.

A prospective observational study was carried out on 9 patients undergoing extracardiac total cavopulmonary connection. Mean age at operation was 4.3 ± 0.6 years, and mean weight 14 ± 2.4 kg. Hepatic stiffness was analysed with Fibro-Scan evaluation immediately before and 4 months after surgery. Results were matched with several perioperative data: pulmonary pressures, conduit size, fenestration, hepatic enzymes and coagulation setting.

Preoperative hepatic stiffness was 6.2 ± 1.5 kPa, with a significant increase to 11.2 ± 4 kPa at a mean follow-up of 4 months (P < 0.01). Mean alanine aminotransferase was 16.9 ± 8.3 mg/dl preoperatively and 16.3 ± 8.7 mg/dl at discharge. Both values showed a significant correlation with liver stiffness raise, their Pearson Correlation Indexes being 0.8 and 0.7, respectively (P < 0.01). Mean aspartate aminotransferase/alanine aminotransferase ratio at discharge was 1.7 ± 0.5 and showed a significant negative correlation with liver stiffness raise, its Pearson Correlation Index being -0.7 (P < 0.01).

Liver stiffness increases rapidly after total cavopulmonary connection and perioperative variations in some liver enzymes appear to correlate with this change. Since a true anatomical damage is known to develop gradually with Fontan circulation, early liver stiffness raise is likely due to parenchymal congestion only. Fibro-Scan can easily recognize and assess the entity of such a change. For these reasons, this diagnostic tool must be considered useful only to monitor liver stiffness changes and evolution with time, but a conventional evaluation of results, like in other acquired hepatic fibrosis, can be misleading.