Predictors of Higher Peak Exercise Oxygen Uptake in a Cohort of Adult Patients with Fontan Circulation

Background/Objectives: Percent achieved of predicted peak exercise oxygen uptake (%VO_2pred) is a prognostic factor for patients with Fontan circulation. The main purpose of this study was to determine predictors of higher %VO_2pred in a cohort of adult Fontan patients. Methods: Medical records of 50 adult Fontan patients who underwent cardiopulmonary exercise testing were reviewed. All patients were divided into two groups according to the mean value of %VO_2pred and, in separate analysis, according to the morphology of the systemic ventricle. Spearman's rank correlation was used to examine the relationship between %VO_2pred and blood biomarkers. Regression analyses were used to identify predictors of %VO_2pred. Results: The median age of all patients was 22 years, and 50% were female. The systemic ventricle was dominant right in 23 patients. Negative correlations were found between %VO_2pred and N-terminal prohormone of brain natriuretic peptide, mean cell hemoglobin concentration, and ferritin, and positive correlations were found between %VO_2pred and total protein, total iron-binding capacity. Higher chronotropic index [CI] (β = 0.31; p = 0.009), higher maximal diastolic blood pressure during CPET [DBP_max] (β = 0.4; p = 0.001), and lower serum concentration of high-sensitivity troponin T [hsTnT] (β = -0.31; p = 0.007) were significantly and independently associated with %VO_2pred. Conclusions: Higher CI and DBP_max and lower hsTnT were identified as independent predictors of %VO_2pred in this cohort. These findings suggest that the absence of chronotropic incompetence is a positive predictor of exercise capacity. Furthermore, hsTnT shows potential as a useful biomarker in this population. Further studies are needed to validate these parameters for clinical assessment and risk stratification in Fontan patients.