This study is looking at differences in metabolism and functional imaging between pulmonary hypertension subjects with normal right ventricular function and persistent right ventricular dysfunction. We will also measure right ventricular metabolic and structural changes using serial 11C-acetate and 18F-FDG PET/CT and cardiac MRI as response to treatment with ranolazine. Subjects undergo imaging procedures at week 0 and week 26 (optional for normal function patients). This is a companion imaging trial for patients who are eligible for the treatment trial entitled "A randomized, double-blind, placebo controlled, multi-center study to assess the effect of ranolazine on outcomes in subjects with pulmonary hypertension and right ventricular dysfunction accompanied by a comparative study of cellular metabolism in subjects with pulmonary hypertension with and without right ventricular dysfunction". Subjects must enroll in companion treatment protocol to qualify for the imaging protocol.