Effect of inhaled iloprost on the exercise function of Fontan patients: a demonstration of concept

Background: Exercise capacity following Fontan surgery is often depressed. An inability to reduce pulmonary vascular resistance appropriately during exercise may contribute to this phenomenon. The aim of this study was to determine whether administration of iloprost, a selective pulmonary vasodilator, would improve exercise function after Fontan procedure.

Methods: Double-blind, randomized, placebo controlled, crossover trial. Patients performed two cardiopulmonary exercise tests (CPX) separated by <1 month. A single nebulizer treatment (iloprost or placebo) was administered before each CPX.

Results: 18 patients aged 12-49 (median 17) years were recruited. Mild throat discomfort developed in 10/18 patients during iloprost administration; all but 1 were able to complete treatment. No symptoms developed during placebo treatments (p<0.001). Two additional patients did not complete CPX: one with atrial flutter; another with developmental issues that precluded adequate CPX. In the 15 remaining subjects oxygen pulse (a surrogate for forward stroke volume) at peak exercise was higher following iloprost (median increase 1.2 ml/beat; p<0.001). Peak VO2 also rose (median increase 1.3 ml/kg/min; p<0.04). Nine patients had peak VO2 <30 ml/kg/min; each of these patients had higher peak VO2 following iloprost. Only 3/6 patients with peak VO2 >30 ml/kg/min had higher peak VO2 following iloprost (p<0.04).

Conclusions: Iloprost improves the peak oxygen pulse and peak VO2 of patients with Fontan physiology and appears to be particularly beneficial among patients with impaired exercise function. Treatment is associated with minor side effects. These findings support the concept of pulmonary vasodilator therapy in Fontan patients with limited functional capacity.