Evaluation of Sildenafil for the Treatment of Moderate Congestive Heart Failure

The purpose of the study is to evaluate whether sildenafil helps treat heart failure. Some patients with heart failure have high blood pressure in the lungs (referred to as "pulmonary hypertension"). Sildenafil is a medication that is used to treat high blood pressure in the lungs and may reduce symptoms of heart failure. Studies have looked at the short-term benefit of sildenafil in patients with congestive heart failure, but this study will look at the longer-term benefits of 12 weeks of therapy with sildenafil.