Pulmonary Restriction in Patients With a Fontan Circulation: DETERMINANTS, DETERIORATION OVER TIME, AND CLINICAL IMPLICATIONS

Purpose: Pulmonary restriction is common in patients with a Fontan circulation and is associated with impaired quality of life. Studies often fail to accurately define pulmonary restriction, and few have investigated its predictors, longitudinal course, and clinical implication. We investigate the prevalence and determinants of pulmonary restriction in patients with a Fontan circulation, the evolution of pulmonary function over time, and the relationship between pulmonary function and exercise capacity. Methods: This longitudinal study included 85 patients with a Fontan circulation who underwent serial pulmonary function measurements and exercise testing over an 11-year period. According to established criteria, pulmonary restriction was defined as a total lung capacity (TLC) z score < −1.645. Results: Mean age ± SD was 20 ± 10 years. Median (IQR) TLC, forced vital capacity (FVC), and diffusing capacity of the lungs for carbon monoxide z scores were −0.98 (−1.98, −0.25), −0.82 (−1.52, −0.19), and −2.30 (−3.04, −1.44). Twenty-eight patients (33%) had pulmonary restriction. A longer time since Fontan completion and undergoing 2 or more thoracotomies increased the odds of developing pulmonary restriction. The FVC z score was associated with log 2 percentage of predicted peak oxygen uptake ( β = .08, P = .025), and FVC z scores declined by 0.06 per year ( P = .009). Conclusion: Pulmonary restriction is prevalent in patients with a Fontan circulation. Multiple thoracotomies and a longer time since Fontan completion predict the development of pulmonary restriction. The FVC, not TLC, is associated with lower exercise tolerance. This emphasizes the importance of muscle-dependent pulmonary ventilation. Finally, FVC z scores are decreased in adolescence and deteriorate faster than in the general population.