Comparison of Echocardiographically-Calculated Fontan Fenestration Gradient and Catheter-Based Measurement

Abstract Background: Patients born with single ventricle physiology typically undergo surgical palliation in three stages, culminating in the Fontan procedure. Assessment of flow across a Fontan fenestration by Doppler Ultrasound theoretically allows for non-invasive estimation of the transpulmonary gradient (TPG). Our objective was to determine the relationship between Doppler-derived mean fenestration gradient (mFG) and direct catheter-based measurements of TPG in patients with fenestrated Fontans. Methods We performed a single-center retrospective cohort study of 59 patients with fenestrated Fontans completed between 2000-2022. The primary outcome was catheter-based measurement of TPG and the primary predictor was mFG from echo performed within six months of the catheterization. Linear regression and R2 were used to determine the relationship between predictors and outcomes. Results Catheter-based measurements of TPG and mFG were weakly correlated (R2=0.382, p<0.001); the regression coefficient was 0.550, with a standard error of 0.09 for every increase in mFG (Cath TPG = 0.55 [mFG] + 1.92). mFG had a slightly better predictive relationship with cath-derived TPG in patients with systemic left ventricles with R2 of 0.47, p<0.004. Conclusion mFG accounts for approximately 38% of the variance in catheter-derived TPG. Although mFG is non-invasive and intuitive, mFG in Fontan patients should be interpreted with caution and direct measurement by cardiac catheterization should be considered.