This study sought to determine whether terbogrel was an effective treatment for primary pulmonary hypertension (PPH) by comparing its efficacy and safety to that of placebo.

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