PDE5A and pulmonary venoocclusive disease: Sildenafil, a specific inhibitor of PDE5, may have a better safety profile due to its mild impact on pulmonary wedge pressure, chronic administration of sildenafil was effective in enhancing exercise capacity of PVOD patient [17], for our patients, we usually started with sildenafil or tadalafil, ambrisentan was sequentially added on if no obvious effects were observed.