 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. 