 Sildenafil Revatio an inhibitor of the phosphodiesterase 5 PDE-5 was used in many individual cases Abrams, Schulze-Neick et al, Heart 2000, some acute studies and two long-term studies in humans to reduce the pulmonary vessel resistance. Significant effects on reduction of the pulmonary vessel resistance were demonstrated for the combination with an inhalational prostanoid Ghofrani et al, Ann Int Med 2002.Good long-term tolerability and effectiveness over a period of two year were demonstrated by this working group. 