Impact of 4D-Flow CMR Parameters on Functional Evaluation of Fontan Circulation.

Abstract

We sought to evaluate the potential clinical role of 4D-flow cardiac magnetic resonance (CMR)-derived energetics and flow parameters in a cohort of patients' post-Fontan palliation. In patients with Fontan circulation who underwent 4D-Flow CMR, streamlines distribution was evaluated, as well a 4D-flow CMR-derived energetics parameters as kinetic energy (KE) and energy loss (EL) normalized by volume. EL/KE index as a marker of flow efficiency was also calculated. Cardiopulmonary exercise test (CPET) was also performed in a subgroup of patients. The population study included 55 patients (mean age 22±11 years). The analysis of the streamlines revealed a preferential distribution of the right superior vena cava flow for the right pulmonary artery (62.5±35.4%) and a mild preferential flow for the left pulmonary artery (52.3±40.6%) of the inferior vena cave-pulmonary arteries (IVC-PA) conduit. Patients with heart failure (HF) presented lower IVC/PA-conduit flow (0.75±0.5 vs 1.3±0.5 l/min/m2, p=0.004) and a higher mean flow-jet angle of the IVC-PA conduit (39.2±22.8 vs 15.2±8.9, p<0.001) than the remaining patients. EL/KE index correlates inversely with VO2/kg/min: R: -0.45, p=0.01 peak, minute ventilation (VE) R: -0.466, p<0.01, maximal voluntary ventilation: R:0.44, p=0.001 and positively with the physiological dead space to the tidal volume ratio (VD/VT) peak: R: 0.58, p<0.01. From our data, lower blood flow in IVC/PA conduit and eccentric flow was associated with HF whereas higher EL/KE index was associated with reduced functional capacity and impaired lung function. Larger studies are needed to confirm our results and to further improve the prognostic role of the 4D-Flow CMR in this challenging population.