Aerobic Capacity of Adults With Fontan Palliation: Disease-Specific Reference Values and Relationship to Outcomes

Patients with Fontan palliation have reduced aerobic capacity because of impaired cardiac, pulmonary, and skeletal muscle function. However, the assessment of aerobic capacity in this population still relies on comparisons with people without cardiovascular disease rather than comparison with the expected aerobic capacity of other Fontan patients. The purpose of this study was to determine the expected aerobic capacity of adults with Fontan palliation.

Adults with Fontan palliation who underwent a cardiopulmonary exercise test at Mayo Clinic (2003-2023) were stratified into quartiles based on the predicted peak oxygen consumption (VO₂). We assessed the correlates of predicted peak VO₂ and the relationship between predicted peak VO₂ quartiles and cardiovascular outcomes (death/transplant).

Of 323 patients (age, 29±9 years; 177 [55%] men), the median peak VO₂ was 19.1 (15.2-23.9) mL/kg per minute, and this corresponds to a predicted peak VO₂ of 51% (range, 19-88; interquartile range, 41-62). After multivariable adjustments, the correlates of predicted peak VO₂ were body mass index (β±SE, -2.61±0.95; 2.61% decrease in predicted peak VO₂ per 5 kg/m² increase in body mass index; P=0.009), systemic saturation (β±SE, 3.65±0.85; 3.65% increase in predicted peak VO₂ per 5% increase in oxygen saturation; P<0.001), and Fontan pressure (β±SE, -1.24±0.22; 1.24% decrease in predicted peak VO₂ per 1 mm Hg increase in Fontan pressures; P<0.001). There was a 47% increase in the risk for death/transplant from a higher predicted peak VO₂ quartile to the next lower quartile (adjusted hazard ratio, 1.47 [95% CI, 1.09-2.05]; P=0.01).

The results of the current study would help calibrate the interpretation of exercise test data in adults with Fontan palliation and improve risk stratification in this population. It also underscores the need to maintain normal Fontan hemodynamics and body weight, which are important determinants of aerobic capacity.