Additional Study Information: This is a clinical research study designed to determine the safety and effectiveness of the TIVUS system, an investigational device used in the treatment of PAH. The TIVUS System is intended to treat patients with pulmonary artery hypertension by injuring the sympathetic nerves surrounding the pulmonary vasculature (denervation) using ultrasonic energy. The information collected from this study will be used to evaluate how well patients do when treated with the TIVUS system both immediately after treatment and over a long period of time (5 years). Treatment of PAH with the TIVUS system involves damaging the sympathetic nerves surrounding the arteries in the lungs with ultrasonic energy. Sympathetic nerves are a part of the nervous system that increases heart rate, narrow blood vessels, and raise blood pressure. A small catheter (a long, flexible tube) is brought to the artery in your lung (the pulmonary artery) through the Jugular Vein in your neck. The device will then deliver the ultrasonic energy to disrupt the nerves in several locations. Once this is completed the device is removed. This procedure is called pulmonary artery denervation (PAD).