Role of Sildenafil for Fontan Associated Liver Disease (SiFALD) Study

All participants will undergo a baseline liver magnetic resonance elastography. The patients with liver stiffness score >2.5 kiloPascal (KPa) [Normal: ≤2.5 KPa] will be enrolled in the study.

In addition to a baseline liver MRE, all participants will undergo cardiac MRI, transthoracic echocardiogram (TTE), FibroSure® (alpha-2 macroglobulin, haptoglobulin, gamma-glutamyltransferase, bilirubin, apolipoprotein A1, and alanine transaminase), and chemistry panel.

This will be a double blinded placebo control study design. All participants will be randomized 1:1 to sildenafil or placebo for a total of 12 months therapy.

Sildenafil will be initiated at 5 mg 3 times per day for the first week, and titrated to 10 mg 3 times per day for the second week and 20 mg 3 times per day from the 3rd week to the end of the study period. The patients will be required to check their pulse rate and blood pressure daily during the first month of drug therapy. Patient who experience hypotension (blood pressure < 90/50 plus symptoms such as dizziness) during dose titration will be asked to remain on the previous tolerated dose. Patients who cannot tolerate 10 mg 3 times daily will be asked to withdraw from the study and will be asked to continue checking their blood pressure for three days after stopping the medication.

After 12 months (+/- 2 weeks) of therapy, all imaging studies (liver MRE, cardiac MRI, TTE) and blood tests (FibroSure® and chemistry panel) will be repeated. A final liver MRE and FibroSure will be performed at 18 months (+/- 2 weeks) for the participants whose 18 months follow-up still falls within the study period.

Adverse event and compliance monitoring: During the first month of enrollment (initiation and dose titration), adverse events will be collected by subject report and by weekly telephone interview with dedicated research personnel. For the rest of the study period, adverse events will be collected by subject report and by monthly telephone interview with dedicated research personnel. The research personnel will be responsible for sending out the monthly supply of medications and obtaining a count of the remaining number pills as a measure of compliance. All participants will be provided with a pamphlet containing all the side effects of sildenafil, and contact information of research team for reporting any adverse event of concerns about the study.