Abstract 15963: Where the Fontan Flows: Longitudinal Trends in Flow Through the Palliated Single Ventricle Circulation

Background:In the past 2 decades patients living with Fontan physiology have had improved life expectancy but continued high rates of morbidity. Alterations in flow equilibrium within this circulation are known to place patients at risk for Fontan morbidity. However little is known regarding how blood flow through the Fontan circuit changes over time. This study uses serial cardiac magnetic resonance (CMR) data to describe longitudinal trends in palliated single ventricle circulation.Methods:This was a retrospective single center study of all patients who underwent Fontan completion from 2008 to 2017 and underwent serial CMRs at ? 2 of the following time points: prior to Fontan, 3-9 months after Fontan and >1 year after Fontan. Flow was measured in the right (RSVC) and left superior vena cava (LSVC), inferior vena cava (IVC), Native Aorta, Neo-Aorta, right (RPA) and left pulmonary artery (LPA) indexed to BSA. Trends were studied using linear mixed effects models with random intercepts.Results:Sixty-three patients were studied; 18 had serial CMRs at 3 time points and 4 patients had MRIs at 4 time points. There was a linear increase in RPA and LPA flow and a linear decrease in SVC flow with time from Fontan (P=0.016 RPA, 0.009 LPA, 0.0001 SVC). Both neo-aortic and IVC flow decreased sharply in the first 1-2 years post Fontan however IVC flow increased after 2 years. This non-linear trend was statistically significant (P<0.0001 IVC, 0.0004 Neo Aorta).Systemic to pulmonary collateral flow decreased in a non-linear fashion the first year after Fontan (p < 0.0001).Conclusion:Serial data demonstrate specific longitudinal trends in vascular flow after conversion to a total cavopulmonary circulation. Early Fontan physiology is characterized a sharp decrease in IVC and neo-aortic flow, and linear increase in pulmonary artery flow over time. This data provides a framework with which serial CMR data can be used to identify patients who have abnormal adaptation to the Fontan circulation.