• Multicentre international randomized double-blind, placebo-controlled trial.

• Eligiblity Criteria
• Patients 50 years of age or older were eligible.
• Ability to provide written informed consent.
• At least one sign and at least one symptom of heart failure on a prespecified list of clinically defined signs and symptoms.
• LVEF >= 45% as measured at the local site by means of echocardiography or radionuclide ventriculography.
• Controlled systolic blood pressure.
• Serum potassium level of < 5.0 mmol per liter.
• History of hospitalization within the previous 12 months, with management of heart failure a major component of the care provided.
• Elevated natriuretic peptide level within 60 days before randomization (a brain natriuretic peptide [BNP] level ≥100 pg per milliliter or an N-terminal pro-BNP [NT- proBNP] level ≥360 pg per milliliter).

• The primary outcome was a composite of death from cardiovascular causes, aborted cardiac arrest, or hospitalization for the management of heart failure.

• Severe systemic illness with a life expectancy < 3 years
• Severe renal dysfunction (eGFR <30 ml per minute per 1.73 m² of body-surface area or a serum creatinine level that was ≥2.5 mg per deciliter [221 µmol per liter])
• Specific coexisting conditions, medications, or acute events

• 3445 patients 50 years of older with symptomatic heart failure and a left ventricular ejection fraction (LVEF) >= 45% were randomized to receive either spironolactone (15 to 45 mg daily) or placebo.

Primary Endpoints

• The primary outcome occurred in 320 of 1722 patients in the spironolactone group (18.6%) and 351 of 1723 patients in the placebo group (20.4%) (hazard ratio, 0.89; 95% confidence interval [CI], 0.77 to 1.04; P=0.14).
• Of the components of the primary outcome, only hospitalization for heart failure had a significantly lower incidence in the spironolactone group than in the placebo group (206 patients [12.0%] vs. 245 patients [14.2%]; hazard ratio, 0.83; 95% CI, 0.69 to 0.99, P=0.04).
• Neither total deaths nor hospitalizations for any reason were significantly reduced by spironolactone.

Secondary Outcomes

• There were no significant differences in rates of myocardial infarction or stroke
• Treatment with spironolactone was associated with increased serum creatinine levels and a doubling of the rate of hyperkalemia (18.7%, vs. 9.1% in the placebo group) but reduced hypokalemia. With frequent monitoring, there were no significant differences in the incidence of serious adverse events, a serum creatinine level of 3.0 mg per deciliter (265 µmol per liter) or higher, or dialysis.