This single center, prospective, open-label trial to assess the safety and efficacy of ranolazine in subjects with pulmonary hypertension associated with left ventricular diastolic dysfunction includes a screening period, 6 month treatment period and a follow up period. Eligible subjects who provide informed consent and who meet all inclusion/exclusion criteria will be enrolled in this study. All subjects will receive active study drug. There is no placebo group or use of control subjects. Treating will begin with 500mg twice daily and increased to 1000mg twice daily as tolerated after 2wks; the tolerated dose will be used for the remainder of the Treatment Period. Ranolazine will be limited to 500 mg BID in patients taking moderate inhibitors of CYP3A, including diltiazem, verapamil, aprepitant, erythromycin, fluconazole, grapefruit juice or grapefruit-containing products. During the Treatment Period subjects will be provided bottles of study medication to take home. Throughout the Treatment Period, subjects will return to the clinic for safety and/or efficacy assessments as well as resupply of Study Medication. Once the Treatment Period is complete, subjects will return to the clinic for a Follow-Up visit 14 days after the last dose of study medication, for a final safety assessment. Other therapies or possibly extension of the ranolazine treatment may be considered after completion of the Treatment Period at the discretion of the Investigator and will be recorded at the follow-up visit. Subjects who continue taking ranolazine (as part of there clinical care), will be asked to return for a 1 year follow up visit for safety and efficacy assessments.

As part of Amendment 2 (submitted November 2013), subjects who continue on ranolazine after the 6 month treatment period (as part of their clinical care) will be asked to return for further follow-up testing to better assess the safety and efficacy of the drug. The visit can be conducted once the patient has been on drug for a total of one year or greater (including the 6 month treatment period). This would replace the 1 Year follow-up visit for subjects who have not yet completed the visit and will be an additional visit for those subjects who have.

Subjects can opt to continue on ranolazine regardless of if they agree to complete the Post Treatment Follow up visit. They do not have to continue with the study after the treatment phase has been completed in order to stay on ranolazine. The PI and study personnel will complete the required forms for the Ranexa Connect application if patient wishes to stay on drug. The Ranexa Connect Program assists patients in obtaining insurance coverage of ranolazine and financial assistance if needed.

This is a 6 month, single center, prospective, open-label trial. All subjects will be receiving active treatment, ranolazine at doses approved by the FDA. Subjects will begin treatment at 500mg twice daily and increase to 1000mg twice daily as tolerated after 2 weeks. Subjects will take study drug twice daily with or without food. Ranolazine will be limited in subjects taking CYP3A including diltiazem, verapamil, arprepitant, erythromycin, fluconazole, grapefruit juice or grapefruit juice containing products. The study will consist of 3 periods: a screening period, a treatment period, and a follow-up period.

Subjects will be asked to come to the study center for 9-10 visits over the course of 6 months. Other therapies or possibly extension of the ranolazine treatment may be considered after completion of the treatment period at the discretion of the Investigator at the follow up visit. Subjects who continue on ranolazine after completion of the treatment period of the study will be asked to return for follow up testing.