Extracardiac predictors of functional capacity in a group of Fontan patients

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.

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.

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.

The median 6MWT distance was 564 m, handgrip strength was 28.3 ± 11.1 kg, and ΔSpO₂ was 4% (IQR: 2-5). Patients with intra-extracardiac Fontan and fenestration exhibited significantly higher ΔSpO₂ (p = 0.03 and p = 0.003, respectively). ΔSpO₂ 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).

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.