Safety and Efficacy of Terbogrel in Patients With Primary Pulmonary Hypertension

Inclusion Criteria: * Primary pulmonary hypertension and New York Health Association (NYHA) chronic heart failure (CHF) functional class II-III * Ability to walk \>= 50 meters on the 6 minute walk test * Resting mean pulmonary artery pressure \> 25 mmHg * Mean right atrial pressure \<= 20 mmHg * Pulmonary capillary wedge pressure \<= 15 mmHg * Cardiac index \> 2.5 L/min2 * SvO2 sat. \> 63% * Male of female at least 18 years old * Signed written informed consent Exclusion Criteria: * Secondary pulmonary hypertension due to lung or systemic diseases * Pregnant of nursing women, or women of childbearing potential who are not using adequate methods of birth control * Concurrent systematic use of aspirin, aspirin like drugs, or non-steroidal anti-inflammatory drugs (NSAIDs) * Surgery of bleeding from gastrointestinal, genitourinary tract, cerebrum or retina within past 6 weeks * History of bleeding diathesis or a platelet count less than 70,000/mm3 * Exercise limited by factors other than fatigue or exertional dyspnea, such as arthritis, claudication, angina, chronic obstructive pulmonary disease, or bronchial asthma * Myocardial infarction, stroke, or transient ischemic attack within the preceding six months * Systolic blood pressure \< 90 mmHg or \> 180 mmHg, or diastolic blood pressure \> 110 mmHg * Known drug or alcohol dependency within one year of entry into the study * Known hypersensitivity to any component of the study formulation, epoprostenol, nitric oxide, or adenosine * Psychiatric or other illness or condition which, in the opinion of the principal investigator, may interfere with study participation, compliance, or other elements of the protocol * Participation in an evaluation of an investigational drug within the past 30 days * Portal hypertension or cirrhosis of the liver * Congenital heart disease e.g., atrial septal defect; patent foramen ovale does not exclude patient from the study * Appetite suppressants such as fenfluramine, dexfenfluramine, and inhibitors of serotonin uptake known to be associated with primary pulmonary hypertension, received within 3 months of entry into the study * HIV positive * Vasodilators. Patients will not receive Ca-channel blockers during the study unless the medication was started prior to the study and the patient has been on a stable dose for at least one month prior to entry