RecruitingPediatric Pulmonary Hypertension Network (PPHNet) Informatics RegistryPatients are being asked to be in this research study because medical researchers hope that by gathering information about a large number of children with pulmonary hypertension over time, their understanding of the disease process will increase and lead to better treatment. Investigators believe that pulmonary hypertension in children is different than pulmonary hypertension in adults and this study will help us understand those differences.