Pulmonary arterial hypertension (PAH) is a progressive disease that results in severe activity limitation and death. There are few treatments for PAH and the available medications are expensive, difficult to administer and have significant toxicities.

(-)-Epicatechin is a non-toxic compound that naturally occurs in foods such as tea, wine and chocolate. Clinical intervention studies using dark chocolate in normal volunteers and subjects at risk for or with established cardiovascular disease have demonstrated improvements in peripheral and coronary vascular endothelial function, blood pressure, lipids, glucose tolerance and inflammatory markers.

Our study intends to examine the hemodynamics effects of purified (-)-epicatechin in subjects with pulmonary arterial hypertension. We hypothesize purified (-)-epicatechin will reduce pulmonary vascular resistance in patients with pulmonary arterial hypertension.

Inclusion Criteria:

• Male or female age 18 or older
• NYHA Class II-!V
• 6 minute walk distance < 450 meters
• Outpatients with suspected WHO group I PAH or and established diagnosis of WHO group I PAH undergoing clinically indicated right heart catheterization
• Written informed consent obtained from subject and ability for subject to comply with the requirements of study

Exclusion Criteria:

• Pregnancy
• Breast feeding
• Systolic blood pressure <100 or >160
• History of migraine headaches
• Allergy or intolerance to chocolate, tea or wine
• Subject is considered unsuitable for the study in the opinion of the investigator, nurse practitioner, or study physician for any other reason