Defining diastolic dysfunction post-Fontan: Threshold, risk factors, and associations with outcomes

Background: Following the Fontan procedure, patients with single ventricle physiology are at high risk of diastolic dysfunction (DD) and elevated end-diastolic pressure (EDP). Objective: This study aims to determine (1) the optimal EDP threshold correlated with adverse outcomes post-Fontan and (2) the clinical and imaging predictors of DD. Methods: The study included patients from the Fontan Outcome Registry using CMR Examinations (FORCE) who underwent cardiac catheterization and cardiac magnetic resonance (CMR) within a 2-year window. The composite outcome was defined as all-cause mortality, sustained atrial or ventricular arrhythmia, plastic bronchitis, protein-losing enteropathy, or listing for transplantation. The EDP cutoff was determined using the lowest Brier score from Cox proportional hazard models. Results: The study included 861 patients (mean age 16.4 ± 9.3 years). Mean EDP was 9.0 ± 3.5 mm Hg, with DD defined at an optimal EDP threshold >13 mm Hg. Patients were followed for a median of 3.6 years after catheterization. By univariable analysis patients with DD were more likely to have Fontan associated liver disease (40% vs 29%, P = .03) and kidney disease (19% vs 6%, P < .001). In multivariable analyses, DD was associated with the composite outcome (HR 3.37, 95% CI: 2.03-5.59, P < .001). Ninety-seven patients (11.3%) had DD. Multivariable analysis demonstrated that older age at catheterization, greater body mass index (BMI), nonleft ventricular morphology, and higher ventricular end-diastolic volume (EDV) were associated with DD. Conclusion: DD, defined as an EDP >13 mm Hg, is linked to over 3-fold higher risk of adverse outcomes. Risk factors for DD include older age, higher BMI, nonleft ventricular morphology, and larger EDV. The presence of risk factors may warrant screening catheterization to identify DD and modify care accordingly.