Despite advances in medical therapy for patients with heart failure, one-third of patients remain limited by fatigue and shortness of breath.

Our previous study concluded that one dose of sildenafil (Viagra) lead to an improvement in heart pressure and exercise capacity.

Currently sildenafil is not FDA approved for the treatment of heart failure.

The purpose of this study is to determine if treatment with sildenafil for 12 weeks in patients with heart failure can improve exercise capacity and quality of life in people with heart failure.

This study will compare two groups of patients. One group will receive sildenafil and the other group will receive a placebo (a pill which looks like sildenafil, but contains no medication).

Patients will undergo a heart catheterization, echocardiogram and exercise stress test. Patients will then take study medication for 12 weeks. A repeat heart catheterization, echocardiogram and exercise stress test will then be performed.

Inclusion Criteria:

Age >18 years Ejection fraction <40% Heart failure limited by fatigue and shortness of breath Pulmonary artery hypertension

Exclusion Criteria:

Patients taking the following medications: nitroglycerine pill/patch/paste, isordil, Imdur, antifungal agents and certain antidepressants.

Patients with a history of optic neuropathy or unexplained visual impairment. Patients with anemia.

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