The purpose of this study is to test the effect of prolonged therapy (24 weeks) with isosorbide dinitrate ± hydralazine on arterial wave reflections, exercise capacity, left ventricular (LV) mass/fibrosis and diastolic function in patients with Heart Failure and Preserved Ejection Fraction (HFPEF). This is a double-blind, placebo-controlled pilot randomized study in which the effects of placebo and 2 vasoactive interventions (isosorbide dinitrate or isosorbide dinitrate + hydralazine) administered for 24 weeks will be assessed in patients with HFPEF. A total of 42 patients with HFPEF will be enrolled across all sites over a 1.5 year period and randomized placebo, isosorbide dinitrate, or isosorbide dinitrate+hydralazine therapy at maximum tolerated doses for 24 weeks. An initial run-in/dose-titration period of 2 weeks will be followed by 24 weeks of randomized therapy at tolerated doses. It is hoped that the results of this study will ultimately lead to an effective treatment for HFPEF which is urgently needed. Since there is minimal risk and potential benefits to medical knowledge and society, the risk / benefit ratio of this study is favorable.

You may be eligible for this study if you meet the following criteria:

• Conditions: Heart failure, heart failure
• Age: 1 years - 99 years
• Gender: All