Older Age at Fontan Completion is Associated with Reduced Lung Volumes and Increased Lung Reactance.

Background: Fontan patients have abnormal lung function, in particular restrictive lung disease and low diffusing capacity of carbon monoxide (DLCO). We sought to further characterise these abnormalities with detailed pulmonary function testing and examine associations with clinical parameters. Methods: 132 Fontan patients across Australia and New Zealand underwent spirometry, with 126 subjects included in final analyses. Measurement of diffusion capacity (DLCO) including its components (alveolar volume (VA) and rate of uptake of CO (KCO)) and oscillometry (reactance (X5) and resistance (R5)) were assessed in a subset of Fontan patients (n = 44) and healthy controls (n = 12). Double diffusion (to assess diffusing capacity of nitric oxide (DLNO), capillary blood volume (Vc), alveolar capillary membrane function (DmCO)) was performed in Fontan patients (n = 18) and healthy controls (n = 12). Results: FEV1 and FVC z-scores were low in Fontan subjects (mean 1.67 +/- 1.24 and 1.61 +/- 1.29, respectively) and correlated with exercise capacity. Compared to controls, z-scores for X5, DLCO, KCO, VA and DLNO were significantly lower in Fontan patients. R5, Vc and DmCO z-scores were preserved. X5 was associated with VA (r = -0.41,p = 0.009) and DmCO (r = -0.61,p = 0.008). Older age at Fontan completion was associated with lower z-scores for FEV1 (r = -0.46,p = 0.002), FVC (r = -0.47,p = 0.002), X5 (r = -0.32,p = 0.033) and VA (r = -0.36,p = 0.022). Conclusion: Fontan patients have a reduced DLCO which is largely driven by low VA. Lung stiffness (X5) is increased which is associated with VA and DmCO. These parameters negatively correlate with older age of Fontan completion suggesting that earlier Fontan completion may have a beneficial effect on lung function.