Background: The Fontan operation creates a total cavopulmonary connection, a circulation in which the importance of pulmonary vascular resistance is magnified. Over time, this circulation leads to deterioration of cardiovascular efficiency associated with a decline in exercise performance. Rigorous clinical trials aimed at improving physiology and guiding pharmacotherapy are lacking. Methods: The FUEL trial (Fontan Udenafil Exercise Longitudinal) was a phase III clinical trial conducted at 30 centers. Participants were randomly assigned udenafil, 87.5 mg twice daily, or placebo in a 1:1 ratio. The primary outcome was the between-group difference in change in oxygen consumption at peak exercise. Secondary outcomes included between-group differences in changes in submaximal exercise at the ventilatory anaerobic threshold, the myocardial performance index, the natural log of the reactive hyperemia index, and serum brain-type natriuretic peptide. Results: Between 2017 and 2019, 30 clinical sites in North America and the Republic of Korea randomly assigned 400 participants with Fontan physiology. The mean age at randomization was 15.5±2 years; 60% of participants were male, and 81% were white. All 400 participants were included in the primary analysis with imputation of the 26-week end point for 21 participants with missing data (11 randomly assigned to udenafil and 10 to placebo). Among randomly assigned participants, peak oxygen consumption increased by 44±245 mL/min (2.8%) in the udenafil group and declined by 3.7±228 mL/min (–0.2%) in the placebo group ( P =0.071). Analysis at ventilatory anaerobic threshold demonstrated improvements in the udenafil group versus the placebo group in oxygen consumption (+33±185 [3.2%] versus –9±193 [–0.9%] mL/min, P =0.012), ventilatory equivalents of carbon dioxide (–0.8 versus –0.06, P =0.014), and work rate (+3.8 versus +0.34 W, P =0.021). There was no an improvement in myocardial performance index (–0.02 vs 0.01, P =0.030), but no change in reactive hyperemia index, or serum brain-type natriuretic peptide level. Conclusions: In the FUEL trial, treatment with udenafil (87.5 mg twice daily) was not associated with an improvement in oxygen consumption at peak exercise but was associated with improvements in multiple measures of exercise performance at the ventilatory anaerobic threshold. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02741115.

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AimsThe Fontan operation has resulted in improved survival in patients with single-ventricle congenital heart disease. As a result, there is a growing population of teenagers and adults with a Fontan circulation. Many co-morbidities have been increasingly recognized in this population due to the unique features of the Fontan circulation. Standardization of how Fontan co-morbid conditions are defined will help facilitate understanding, consistency and interpretability of research and clinical experience. Unifying common language usage in Fontan is a critical precursor step for data comparison of research findings and clinical outcomes and ultimately accelerating improvements in management for this growing group of patients. This manuscript aimed to create unified definitions for morbidities seen after the Fontan palliation. Methods In association of many congenital heart disease organizations, this work used Delphi methodology to reach a broad consensus among recognized experts regarding commonly used terms in Fontan care and research. Each definition underwent at least three rounds of revisions to reach a final definition through surveys sent to experts in the field of single-ventricle care. Results The process of reaching a consensus on multiple morbidities associated with the Fontan procedure is summarized in this manuscript. The different versions that preceded reaching the consensus are also presented in the Supporting Information. Table 1 represents the final definitions according to the consensus. Conclusions We propose the use of these definitions for clinical care, future research studies, registry development and clinical trials.

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Background Advancements in the field, including novel procedures and multiple interventions, require an updated approach to accurately assess patient risk. This study aims to modernize patient hemodynamic and procedural risk classification through the creation of risk assessment tools to be used in congenital cardiac catheterization. Methods and Results Data were collected for all cases performed at sites participating in the C3PO (Congenital Cardiac Catheterization Project on Outcomes) multicenter registry. Between January 2014 and December 2017, 23 119 cases were recorded in 13 participating institutions, of which 88% of patients were <18 years of age and 25% <1 year of age; a high‐severity adverse event occurred in 1193 (5.2%). Case types were defined by procedure(s) performed and grouped on the basis of association with the outcome, high‐severity adverse event. Thirty‐four unique case types were determined and stratified into 6 risk categories. Six hemodynamic indicator variables were empirically assessed, and a novel hemodynamic vulnerability score was determined by the frequency of high‐severity adverse events. In a multivariable model, case‐type risk category (odds ratios for category: 0=0.46, 1=1.00, 2=1.40, 3=2.68, 4=3.64, and 5=5.25; all P ≤0.005) and hemodynamic vulnerability score (odds ratio for score: 0=1.00, 1=1.27, 2=1.89, and ≥3=2.03; all P ≤0.006) remained independent predictors of patient risk. Conclusions These case‐type risk categories and the weighted hemodynamic vulnerability score both serve as independent predictors of patient risk for high‐severity adverse events. This contemporary procedure‐type risk metric and weighted hemodynamic vulnerability score will improve our understanding of patient and procedural outcomes.

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IntroductionSingle ventricle diastolic dysfunction and hepatic fibrosis are frequently observed in patients with a Fontan circulation. The relationship between adverse haemodynamics and end-organ fibrosis has not been investigated in adolescents and young adults with Fontan circulation.MethodsProspective observational study of Fontan patients who had a cardiac catheterisation. Cardiac MRI with T1 mapping was obtained to measure extracellular volume (ECV), a marker of myocardial fibrosis. Hepatic magnetic resonance elastography was performed to assess liver shear stiffness. Serum biomarkers of fibrosis including matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) were measured. Very high ECV was defined as >30% and elevated serum biomarkers as >75th percentile for each biomarker.Results25 Fontan patients (52% female) with mean age of 16.3±6.8 years were included. Mean ECV was 28%±5%. There was a significant correlation between ECV and systemic ventricular end-diastolic pressure (r=0.42, p=0.03) and between ECV and liver stiffness (r=0.45, p=0.05). Patients with elevated ECV demonstrated elevations in MMPs and TIMPs. Similarly, patients with elevated MMPs and TIMPs had greater liver stiffness compared with patients with normal levels of these biomarkers.ConclusionsIn Fontan patients, cardiac magnetic resonance evidence of myocardial fibrosis is associated with diastolic dysfunction, increased liver stiffness and elevated circulating biomarkers of fibrosis. These findings suggest the presence of a profibrotic milieu, with end-organ implications, in some patients with Fontan circulation.

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