Evaluation of pulmonary endothelial function in Fontan patients

Objectives: Pulmonary endothelial dysfunction due to a loss of pulsatile pulmonary blood flow is thought to be a major contributor in the development of increased pulmonary vascular resistance (PVR) in patients with a Fontan circulation. We sought to evaluate pulmonary endothelial dysfunction by vasodilator response to acetylcholine in children and adolescents with Fontan hemodynamics.

Methods: Twenty-one Fontan patients with a median age of 10.7 years (range, 3.4-30.0 years) underwent invasive cardiac catheterization, including intra-arterial Doppler and pressure measurements in a segmental pulmonary artery. Pulmonary flow reserve (PFR) was quantified as the change of average peak velocity in response to acetylcholine infusion. Local PVR was assessed by the ratio of local pressure and blood flow velocity.

Results: Average peak velocity significantly increased from 16.4 ± 6.6 cm/s to 20.1 ± 6.4 cm/s (P = .002) resulting in a mean PFR of 1.28 ± 0.37. Local PVR dropped from 0.72 ± 0.32 mm Hg/cm/s to 0.57 ± 0.20 mm Hg/cm/s (n = 19; P = .01). A significant relationship was found between baseline local PVR and PFR (r = 0.73; P = .0006) as well as between PFR and the percent decrease in local PVR (r = 0.85; P < .0001). In addition, percentage decrease in local PVR correlated with New York Heart Association functional class, whereas neither PFR nor local PVR correlated with global PVR.

Conclusions: The assessment of PFR and local PVR may help to evaluate adverse pulmonary vascular remodeling in Fontan patients as an adjunct to the usual catheterization protocol, particularly given the difficulties in assessing global PVR in these patients. Future research is required to study whether impaired local pulmonary endothelial function may be associated with Fontan failure.