Extracardiac predictors of functional capacity in a group of Fontan patients

Abstract Background: The Fontan procedure, a palliative surgical approach for single-ventricle physiology, has significantly improved long-term survival. However, it is frequently associated with reduced exercise capacity and multiorgan dysfunction. In this context, peripheral muscle function and body composition may influence functional outcomes. Objective: The aim of the study was to evaluate the relationships among body composition, handgrip strength, and functional capacity in Fontan patients, as well as to investigate the impact of Fontan-related variables on these parameters. Methods: This single-centre study included 30 clinically stable patients (age range: 7.0–33.0 years) with Fontan circulation. Data collected included pre-operative primary diagnosis, pre-Fontan mean pulmonary artery pressure, and laboratory parameters such as B-type natriuretic peptide, haemoglobin, creatinine, alanine aminotransferase, aspartate aminotransferase, albumin, and uric acid levels. 6-minute walk test (6MWT), handgrip strength, and body composition via bioelectrical impedance were assessed. Correlation and subgroup analyses were performed according to pre-Fontan surgery history, Bidirectional Glenn, Fontan type, fenestration, and other clinical factors. Results: The median 6MWT distance was 564 m, handgrip strength was 28.3 ± 11.1 kg, and ΔSpO 2 was 4% (IQR: 2–5). Patients with intra-extracardiac Fontan and fenestration exhibited significantly higher ΔSpO 2 ( p = 0.03 and p = 0.003, respectively). ΔSpO 2 was inversely correlated with 6MWT distance ( r = −0.531, p = 0.008) and handgrip strength ( r = −0.472, p = 0.017). Fat-free mass was positively correlated with both 6MWT distance ( r = 0.598, p < 0.001) and handgrip strength ( r = 0.537, p = 0.002). Red cell distribution width was negatively correlated with 6MWT ( r = −0.631, p < 0.001) and grip strength ( r = −0.413, p = 0.029). Conclusion: In Fontan patients, reduced handgrip strength, lower fat-free mass, and greater post-exercise oxygen desaturation were associated with impaired exercise capacity, supporting the clinical value of simple functional and muscle strength assessments in routine follow-up.