O0343 Oct.3: 2:37pm - Smaller Fontan Pathway is Associated with Fontan Failure

Background
The Fontan circulation is vulnerable to any flow restriction in the Fontan pathway. We measured the minimal cross-sectional area (CSA) of the Fontan circuit via cardiac magnetic resonance imaging (CMR) and assessed associations with physiologic indices and outcomes.
Methods
The minimum cross sectional area (CSA) of the Fontan was calculated using the narrowest dimensions within the Fontan on a 3D gated respiratory navigated MRA sequence. CSA of the Fontan was calculated by incorporating the diameters, measured by (CMR), of the narrowest point in the Fontan pathway into the area equation for an ellipse. The primary outcome of Fontan failure included a composite of death, transplant, ventricular assist device (VAD) placement, and escalation of diuretics. Receiver operator characteristic (ROC) analysis was performed to determine a threshold of Fontan CSA and minimum diameter that correlated with the primary outcome using a Youden index. Log-rank test was used for univariate survival analysis to assess the relationship of Fontan CSA and minimum dimension with the primary outcome.
Results
Forty-nine patients (median age 23 years, IQR 19-26, range 8-37) with a total cavopulmonary anastomosis (extracardiac conduit, n=23; lateral tunnel, n=26) were included. Median follow-up after CMR was 30 months (IQR 14-52). The primary outcome of Fontan failure occurred in 11 patients (22%). Fontan CSA was significantly lower in patients who experienced Fontan failure (199±67 vs 288±130 mm2, p=0.005). ROC curve analysis showed an area under the curve (AUC) of 0.728; CSA threshold of 234 mm2 was 89% sensitive and 58% specific for the primary outcome. The AUC for minimal Fontan dimension was 0.699 with a threshold of 15 mm, providing 89% sensitivity and 51% specificity. Kaplan-Meier analysis demonstrated patients with Fontan CSA <234 mm2 were more likely to experience Fontan failure over time (HR= 8.10, 95%, p=0.015; Figure 2). Similarly, patients with minimum Fontan diameter <15 mm were more likely to experience Fontan failure over time (HR=8.94, 95%, p=0.01). Fontan cross sectional area was significantly larger in patients with lateral tunnel Fontan compared to extracardiac conduit Fontan (333±144, 210±51 mm2, p=0.0003) and patients with an extracardiac conduit, compared to lateral tunnel Fontan, were more likely to have a Fontan dimension <15 mm (odds ratio=7.7, 95% CI 1.12-2.16, p=0.008). There was no significant difference in the rate of Fontan failure between the extracardiac and lateral tunnel Fontan groups.
Conclusions
Fontan narrowing is associated with adverse outcomes and was more common in extracardiac conduit Fontans. Further studies are needed to determine the cause of narrowing and whether stenting may improve the outcomes associated with Fontan circuit narrowing.