Randomized Controlled Study of Sildenafil in Children and Young Adults With Mild to Moderate Cystic Fibrosis Lung Disease

Cystic Fibrosis (CF), the most common inherited disease in Caucasians, is characterized by chronic pulmonary inflammation and progressive loss of gas exchange units that eventually results in respiratory failure. There is strong evidence that, in CF, abnormally low perfusion carries a high risk of death independent from the presence of pulmonary hypertension. However, the evolution of pulmonary vascular disease in CF and how it might contribute to the rate of decline in lung function is not known. Our knowledge remains limited to the results of old observational studies which concluded that the major causes of pulmonary vascular remodeling and hypertension in CF are hypoxic respiratory failure and destruction of lung tissue. Our recent data obtained by state-of-the-art Magnetic Resonance Imaging (MRI) of the pulmonary circulation, challenges the existing paradigm. We demonstrate that in the absence of hypoxia, significant changes in pulmonary perfusion and in surrogate measures of vascular resistance as well as in collateral blood flow begin early in the course of CF. Newly developed therapeutics have altered dramatically the course of patients suffering from pulmonary vascular disease. Through this 8 week trial, we will examine by Magnetic Resonance Imaging the effect of Sildenafil on pulmonary perfusion and systemic vascularization of the lungs in subjects with mild to moderate disease.