Fibrosis and the Fontan

Spironolactone is a mild diuretic. Drug dosage will be those used clinically and per the CHOP formulary: 3 mg/kg/day in divided doses every 6-24 hours; the drug will be weight adjusted every \~0.5 kg with a maximum dosage of 200 mg/24 hours. Maximum single dose is 100 mg. Spironolactone, the aldosterone antagonist to be utilized in Specific Aim 2 of this study, is FDA approved, has been on the market for many years and is routinely administered to all types of children with congenital heart disease including SV patients. The choice of which patient this should be administered to is up to the clinician and their patients and therefore, not all SV patients are on this medication.