This clinical investigation is a prospective, non-randomized, single-arm, multi-center early feasibility study of the Aria CV Pulmonary Hypertension (PH) System implanted in patients with pulmonary arterial hypertension (PAH). The device will be implanted in the pulmonary artery and the gas reservoir of the device will be in the abdominal cavity. The purpose of this study is to validate that the clinical use of the Aria CV PH System is safe for the patient, and to evaluate its performance in treating patients with PAH. Some procedures involved in the study include but not limited too: Questionnaires, physical exams, right heart catherization, echocardiograms, blood work and more. The study will be conducted in a maximum of 10 centers in the United States. Up to 45 patients will be consented, and up to 15 patients will receive implants. There is a total of 11 visits over the course of 2.5 years for the study. Because this is an investigational device under the FDA, there may be risk that include but are not limited to: arrhythmia, device infection, endocarditis, and heart failure. If the Aria CV device performs as intended, you may potentially benefit from reduction in or relief of symptoms caused by PH, and depending on your overall health conditions, prolonged life expectancy and/or improvement in your overall quality of life.