Abstract Body (Do not enter title and authors here): Introduction: Single ventricle patients following Fontan surgery may experience significant adverse outcomes. Hemodynamic metrics derived from image-based computational fluid dynamics (CFD) analysis could potentially serve as predictors.

Hypothesis: CFD-based measures can prognosticate the consequences of Fontan surgery.

Methods: This study randomly selected 217 Fontan patients who presented for cardiac magnetic resonance (CMR) from 2004-present obtaining anatomy and flows in the cavae and pulmonary arteries to obtain CFD. Hemodynamic metrics were indexed power loss (iPL, unitless) and resistance to flow in the Fontan connection (R_TCPC , in WU). Recorded adverse events (AEs) included death, transplantation, cardiac arrest, admission to the cardiac intensive care unit, pleural effusion, catheterization, pacemaker implantation, protein-losing enteropathy, plastic bronchitis, liver fibrosis and cirrhosis, heart failure, and sustained ventricular tachycardia (VT). Independent two-sample Student's t-tests or Mann-Whitney tests were conducted depending on the normality of the data. Statistical significance was set at p < 0.05.

Results: Age at initial CMR was 12.9 ± 8.2 years, with 37 patients undergoing a second CMR at 16.8 ± 8.1 years. Follow-up occurred 5.1 ± 2.6 years after the initial CMR. The number of patients who experienced an outcome is in Table 1. In the cross-sectional study (n = 217, Table 2), both iPL and R_TCPC were significantly correlated with subsequent occurrence of AEs. Higher iPL was significantly associated with liver fibrosis (p = 0.027) and cirrhosis (p = 0.042) and showed a borderline statistical significance for death (p = 0.055). Higher R_TCPC predicted liver cirrhosis (p = 0.043) and death (p = 0.045), with borderline significance for liver fibrosis (p = 0.058). The longitudinal study (n = 36, Table 3) demonstrated that changes in R_TCPC predicted death (p = 0.029), while changes in iPL were borderline significant (p = 0.058). Additionally, changes in R_TCPC were also significantly correlated with sustained VT.

Conclusion: CFD-derived hemodynamics from CMR demonstrated promise as an important predictor of adverse events in single ventricle patients after Fontan. A larger prospective trial is warranted.