The purpose of the study is to collect information about the potential benefit and safety of low dose spironolactone for a patient with diastolic heart failure (DHF) and to determine whether spironolactone can cause the patient's condition to improve.

Subjects with diastolic heart failure defined based on clinical symptoms, echocardiography diastology parameters and brain natriuretic peptide level will be randomized in a 1:1 fashion to either placebo or spironolactone 25mg daily for 6 months. They will be assessed over this 6 month period for improvement in exercise capacity, clinical symptoms, echocardiography diastology parameters, and biomarkers specific for heart failure. Safety of spironolactone in this patient population will also be assessed by recording adverse events and following electrolytes, blood urea nitrogen, and creatinine levels.

Inclusion Criteria:

• Women who are 18 years of age or older.
• Women with clinical heart failure for > 2 months.
• Women with left ventricular ejection fraction > 50% within 2 months of screening.
• Women with New York Heart Association class II or III heart failure symptoms.
• Brain Natriuretic Peptide > 62 pg/ml within 2 months of screening.
• Patient on angiotensin converting enzyme inhibitor or angiotensin receptor blocker therapy for at least 1 month.
• Blood Pressure no more than 150/95.
• Patient able to walk more than 50 meters at the time of enrollment.
• Signed informed consent.

Exclusion Criteria:

• Current treatment with spironolactone.
• Severe hepatic impairment.
• Creatinine > 2.5 mg/dl
• Potassium > 5.0 mEq/L
• Intolerance to spironolactone in the past.
• Significant valvular heart disease, pericardial disease, or severe chronic lung disease with cor pulmonale.
• Unstable angina or myocardial infarction within the past 4 weeks.
• Severe peripheral vascular disease or other physical conditions that would limit the walking distance.
• Pregnant or lactating females.
• Participation in any other drug trial within 30 days prior to randomization.
• Inability to provide informed consent.