 Study design: single-center, prospective, randomized, placebo controlled study. Study population: 52 patients with HFpEF and PH Intervention : One group receives three times daily 20 mg Sildenafil for 2 weeks followed by three times daily 60 mg Sildenafil for 10 weeks. The other group receives three times daily 20 mg of Placebo, followed by 3 times daily 60 mg placebo. 