Discordances in Kinetic Energy Between the Superior Cavopulmonary Connection and Single Ventricle Are Associated With Suboptimal Fontan Outcomes: A Pre-Fontan 4-Dimensional Flow Study.

Background: Patients with functional single ventricle (SV) are at risk for adverse outcomes after staged palliation from the superior cavopulmonary connection (SCPC) to the Fontan. Current pre-Fontan assessment by cardiac magnetic resonance and cardiac catheterization includes measuring atrioventricular valve regurgitation, aortopulmonary collateral burden, and pressures. Four-dimensional flow can quantify complex flows representing hemodynamic inefficiency. This study determined the clinical significance of kinetic energy (KE) and viscous energy loss in patients before the Fontan procedure using 4-dimensional flow.

Methods and results: This was a retrospective analysis of patients before the Fontan procedure who underwent ferumoxytol-enhanced cardiac magnetic resonance and same-day catheterization. Four-dimensional flow data sets were analyzed using ITFlow (CardioFlowDesign) to measure KE/viscous energy loss in the atrium, SV, and SCPC. A composite outcome was defined by rejected Fontan candidacy, prolonged hospitalization, lymphatic dysfunction, or heart failure. The relationship between these outcomes and KE/viscous energy loss was assessed by bivariable and multivariable logistic regression analyses as appropriate. Sixty-five patients (3.9±1.5 years, 0.64±0.1 m²) were included. Fifty (77%) proceeded to Fontan operation with median hospitalization time of 8.5 (interquartile range, 7-12.7) days. Twenty-six (40%) experienced a composite outcome, including 9 with rejected candidacy. Lower SCPC flow was associated with an outcome (P=0.042). Meanwhile, higher SV KE and lower SCPC KE were independently associated with composite outcome (odds ratio, 3.63 [95% CI, 1.32-13.2]; P=0.0263; odds ratio, 0.906 [95% CI, 0.814-0.980]; P=0.0377). Higher SV KE and lower SCPC KE corresponded to significant atrioventricular valve regurgitation, higher aortopulmonary collateral burden, and higher cathetherization pressures.

Conclusions: Four-dimensional flow analysis provides insight into SV hemodynamics and is associated with short-term outcomes. Future work will analyze the longitudinal implications for patients undergoing the Fontan procedure.