Rt Ventricular Substrate Metabolism as a Predictor of Rt Heart Failure in Patients With Pulmonary Arterial Hypertension

Inclusion Criteria:(PATIENTS) * Patients with diagnosis of Category 1 pulmonary arterial hypertension due to any of the following: idiopathic, familial, associated with connective tissue disease, HIV disease or anorexigen use. * All patients who will require a right heart catheterization for further clinical management and/or diagnosis. * Patients will be considered eligible if they have no significant coronary artery disease (stenosis \> 70% in a proximal or mid major coronary artery) or moderate coronary artery disease (60-70%) with abnormal left ventricular function (EF\<50%) * Patients will be considered eligible in the absence of current or recent evidence of right heart failure. * No previous hospital admission or requirements of intravenous diuretics for right heart failure within 6 months of enrolment. * No increase in oral diuretics to control fluid volume within 6 months prior to enrolment * No current symptoms and signs of fluid retention or right heart strain, including any of the following: development of new ascites or peripheral edema \> = 2+, JVP \>7 cm above the sternal angle or a right atrial pressure \>14 mmHg at the time of right heart catheterization. * In addition, we will include a small cohort of up to 15 patients with PAH and current RHF. Exclusion Criteria: * Patients with known significant coronary artery disease(defined as known stenosis \>70% in a proximal or mid major artery or moderate coronary artery disease (60-70%)in a coronary artery and associated left ventricular ejection fraction \<50%. * Patients with diabetes mellitus who require the use of oral hypoglycemics and or insulin. * Implantable metal devices, incompatible with magnetic resonance imaging. * Other contraindications of magnetic resonance imaging. Normal Control Subjects: * Subjects will have no known cardiac or pulmonary disease. * Normal ventricular function and estimated pulmonary pressures on echocardiogram.