The researchers hypothesize that the addition of nesiritide to standard therapy will prevent worsening of renal function in patients admitted to the hospital with decompensated heart failure and renal dysfunction relative to standard therapy alone.

Inclusion Criteria:

• Decompensated heart failure hospitalization with at least 1 symptom and 1 sign of elevated filling pressures
• Admission estimated creatinine clearance =< 50 cc/min.

Exclusion Criteria:

• Systolic blood pressure < 85 mm Hg
• Cardiogenic shock
• Volume depletion
• Myocardial infarction, unstable angina within last 30 days
• Significant valvular stenosis, hypertrophic/restrictive cardiomyopathy, or constrictive pericarditis
• Chronic hemodialysis
• Anticipated major procedure during hospitalization i.e. left heart catheterization, surgery, or transplantation
• Enrolled in another research protocol within last 30 days.