Predictors of Poor Functional Status in Adult Fontan Patients Living at Moderate Altitude.

Patients who have undergone Fontan palliation have reduced exercise tolerance measured by maximal oxygen consumption (VO2 max). Declining exercise capacity is associated with increased morbidity and mortality. The impact of hemodynamics and other variables on this population's functional status is not well understood. This study sought to identify variables that predict low VO2 max in Fontan patients living at moderate altitude (5,000-8,000 feet). We performed a retrospective cohort study of 44 adult Fontan patients living at moderate altitude who had undergone cardiopulmonary exercise testing (CPET) and cardiac catheterization. We evaluated hemodynamic parameters measured during catheterization, imaging results, and laboratory studies for correlation with VO2 max measured during CPET. Our study cohort (median age 30 years, 52% female) had exercise impairment with mean VO2 max of 21.6 mL/kg/min. Higher trans-pulmonary gradient (TPG) (p < 0.001) and mean pulmonary artery (PA) pressure (p = 0.013) were predictors of lower maximal and submaximal VO2. Higher BNP values correlated with lower VO2 max (p = 0.01). Platelet count, GGT, albumin, and pulmonary vasodilator therapy did not correlate with VO2 max. None of the studied variables were associated with higher minute ventilation to peak carbon dioxide production (VE/VCO2 slope) or change in VO2 max over time. In conclusion, higher TPG and mean PA pressure predicted lower exercise tolerance amongst our cohort of adult Fontan patients living at moderate altitude. Future studies are needed to determine if these clinical variables represent viable therapeutic targets that could result in improved exercise tolerance and outcomes in patients with Fontan circulation.