Reversing Endothelial and Diastolic Dysfunction and Improving Collagen Turnover in Diastolic Heart Failure

Inclusion Criteria: Patients must meet all of the following inclusion criteria to be eligible for enrollment into the study: 1. Male or non-pregnant female (if female, either post-menopausal, or if of child-bearing potential, using adequate contraception e.g. hormonal or barrier methods, or surgically sterile, and not lactating) 2. Age \>/= 18 years of age 3. Present or prior history of symptoms of heart failure (dyspnea, fatigue) consistent with diagnosis of diastolic heart failure, following optimized medical therapy including blood pressure control with ACE inhibitors and/or beta-blockers for 2 weeks or over. 4. Echocardiographic evidence of preserved left ventricular systolic function (LVEF \>/= 45%) and evidence of diastolic dysfunction (by transmitral inflow, pulmonary venous flow, color M-mode and/or tissue Doppler). 5. Signed informed consent Exclusion Criteria: The presence of any of the following will exclude a patient from study enrollment: 1. Unwilling to participate for the 9-month duration of the study 2. Significant primary valvular, pulmonary or congenital cardiac disease believed to be the cause of dyspnea 3. Life expectancy or planned cardiac transplantation \<9 months 4. History of hypertrophic obstructive cardiomyopathy 5. Unstable angina or ischemia requiring revascularization 6. Renal insufficiency (Cr \>2.0 mg/dL in males and \>1.8 mg/dl in females, or modified Cockcroft-Gault estimate of creatinine clearance \<30 mL/min) at enrollment 7. Known hypersensitivity to spironolactone or eplerenone 8. Decompensated heart failure or clinical evidence of instability at the time of enrollment 9 History of hyperkalemia (\>6.0 mg/dL) with spironolactone 10\. Use of spironolactone or amiloride within 30 days 11. Poorly controlled seating blood pressure at the time of drug initiation: * Systolic blood pressure \>160 mmHg; and/or * Diastolic blood pressure \>100 mmHg