Growth of the Fontan pathway and its association with long-term outcomes.

Abstract

To characterize longitudinal changes in lateral tunnel (LT) and extracardiac conduit (EC) Fontan pathway geometry and flow dynamics and to investigate whether these parameters mediate differences in outcomes by Fontan type. Patients who underwent Fontan at our institution between 2000 and 2017 and were evaluated with post-Fontan computed tomography (CT)/magnetic resonance imaging (MRI) were reviewed retrospectively. Three-dimensional segmentations of the Fontan pathways were generated. Indexed power loss (iPL) was estimated using computational fluid dynamics in the context of patient-specific flow measurements and segmentations. Fontan failure was defined as a composite of mortality, heart transplantation, chylothorax, protein-losing enteropathy, plastic bronchitis, and hepatic dysfunction. Of 207 patients (LT, 166; EC, 41) who met the study criteria, 69 (LT, 54; EC, 15) had multiple post-Fontan CT/MRI examinations. Fontan pathway volume increased significantly within the LT cohort (1.6 mL/year; P < .001), but there was no significant change in the volume of EC Fontans (0.4 mL/year; P = .07). When adjusting for body surface area, LT Fontans continued to display increased volume (P = .006), while EC Fontans showed marked decreases (P = .026). The iPL of LT Fontans remained stable; however, there was a significant increase in iPL for patients in the EC cohort (P = .018). LT patients had lower rates of Fontan failure compared to EC patients (P = .002, log-rank test). Mediation analysis revealed that volume mediated ∼20% of the protective effects of the LT technique on the occurrence of Fontan failure at 10 years. LT Fontan pathways exhibited superior growth characteristics and sustained flow efficiency compared to EC Fontan pathways. The LT technique also was associated with improved outcomes, a finding that may be attributable to favorable geometry.