FIG 73.27 Kaplan-Meier survival curve demonstrating 5-year survival in each group Survival of patients with venovenous collaterals undergoing embolization was only 74% compared with 92% in those patients who did not have embolization VVC, Venovenous collaterall (From Poterucha JT, Johnson JN, Taggart NW, et al Embolization of veno-venous collaterals after the Fontan operation is associated with decreased survival Congenit Heart Dis 2015;10:E230–E236.) Aortopulmonary Collateral Embolization Aortopulmonary collateral vessels make a significant contribution to cardiac output and effective pulmonary blood flow in the Fontan circulation.347,348 The magnitude of this contribution may inversely related to pulmonary artery size.356 This portion of cardiac output is recirculated through the pulmonary circulation and presents a volume load to the systemic ventricle Nevertheless, some have postulated that aortopulmonary collateral flow may be beneficial because it provides a degree of pulsatility to pulmonary flow with a beneficial effect on endothelial function It may also reduce the risk of pulmonary AV malformations by providing a source of “hepatic factor” to a lung that receives little flow from the inferior vena cava Coil occlusion of these vessels is rarely indicated outside the immediate postoperative period, except in the occasional patient with increased volume load and atrioventricular valve regurgitation or deteriorating ventricular function This small subset of patients has a high risk of Fontan failure; in one report, more than a third of patients who underwent coil occlusion of aortopulmonary collaterals after the Fontan procedure were subsequently transplanted or died.357 Management of Fontan Failure Definitions Fontan failure can be loosely defined as a clinical syndrome in which the circulation can no longer meet the metabolic demands of the body Although this definition is similar to that of heart failure,358 there are important differences Fontan failure is a heterogeneous syndrome that involves multiple organ systems The chronic elevation of CVP and the lack of pulsatility within the pulmonary circulation are associated with gradual and progressive pathologic changes that involve the entire body in varying degrees of severity and in varying combinations Thus the interplay between the organ systems becomes deranged in a multitude of ways that differ between patients (Table 73.4) There are notable differences in Fontan failure between adults and children, with ventricular dysfunction being a more prominent feature in children and organ system dysfunction being a more prominent feature in adults These differences may be explained by the observation that children with adequate ventricular function are more likely to survive to adulthood and go on to develop the organ system complications of the Fontan circulation.71,359 Table 73.4 Organ System Disease Processes Associated With the Fontan Circulation Organ System Lungs Liver Kidneys Heart Pulmonary vascular remodeling and increased pulmonary vascular resistance (unrestricted blood flow in infancy, passive nonpulsatile flow) Decreased pulmonary vascular capacitance endothelial dysfunction, aortopulmonary collaterals due to the lack of hepatic fluent and/or the loss of pulsatility Hepatopulmonary syndrome and portopulmonary hypertension Restrictive lung disease (developmental, prior chest surgeries, cardiomegaly, abnormal alveolization, and secondary to pulmonary vascular abnormalities) Plastic bronchitis Sinus of fibrosis, centrilobular necrosis, and hepatic cirrhosis with increased risk of hepatocellular carcinoma With increasing portal vein hypertension, the hepatic arterial buffer reflex preserves hepatic perfusion by way of dilating splanchnic and systemic circulations and reducing the systemic vascular resistance Reduced renal perfusion as a result of reduced cardiac output and/or renal congestion Cardiorenal syndrome Arrhythmias Systolic dysfunction Diastolic dysfunction