This multicenter, randomized, double-blinded pilot study compares the clinical effects, safety profile, and economic impact of standard therapy plus Natrecor® to standard therapy plus placebo in the treatment of acutely decompensated CHF in an Emergency Department/Observation Unit setting. Study drug (Natrecor® or placebo) is administered as a bolus of 2 mcg/kg over approximately 60 seconds, immediately followed by a fixed-rate infusion of 0.01 mcg/kg/min for at least 12 hours. Subjects who continue to receive study drug and who remain in the Emergency Department/Observation Unit beyond 12 hours, up to 24 hours, have vital signs measured at 18 hours, 24 hours, immediately before discontinuation of study drug, and at 30 minutes, 1 hour, and 2 hours after discontinuation of study drug. Also, global clinical and dyspnea (difficulty breathing and shortness of breath) evaluations, and a visual monitoring scale for dyspnea, are completed at the time of termination of study drug in the Emergency Department/Observation Unit, or admission to the hospital. The health-economic analysis focuses on resource utilization and cost of care for initial treatment in the Emergency Department/Observation Unit and inpatient facility (if admitted), as well as any subsequent treatment in an Emergency Department or acute inpatient facility within the 30-day study period.