Human B-type Natriuretic Peptide (BNP) (Nesiritide) to Help Heart, Kidney, and Hormonal Functions in Persons With Lower Heart Pumping Function

The following are done for screening procedures to determine if patients are eligible for this study: blood count, kidney and liver blood tests. Patients will complete a 6-minute walk test. Patients will be instructed to follow a no-added-salt diet for 1-3 weeks before the study and for the whole duration of the study. Diet instructions will be given to the patient and the patient will collect his/her urine for 24 hours before the active study day. Patients will need to avoid strenuous exercise and abstain from smoking, alcohol, and caffeine for 3 days prior to the study days. Patients will remain on their regular medications.