Inclusion Criteria:

• History of NYHA (New York Heart Association) Class III or IV congestive heart failure (CHF)
• Has symptomatic, decompensated CHF for which inpatient therapy with either dobutamine or Natrecor®, administered as a single intravenous vasoactive agent (drugs that influence the tone and caliber of blood vessels) with or without diuretics, is deemed appropriate
• Receiving stable doses of oral antiarrhythmic medications (medications that help regulate irregular heart beats) for at least the 48 hours before starting study drug, or receiving no antiarrhythmic medications

Exclusion Criteria:

• Cannot tolerate a 24-Hour Baseline Holter Monitoring Period without intravenous vasoactive medications, and/or cannot tolerate the specified washout period (if applicable) of intravenous vasoactive medications before starting the baseline Holter monitoring
• Has systolic blood pressure consistently < 85 mm Hg, cardiogenic shock, or other evidence of significant hemodynamic instability requiring the immediate institution of inotropic/pressor support
• Has a clinical condition expected to require therapy with more than one intravenous vasoactive agent or Dopamine during the 24-Hour Treatment Holter Monitoring Period
• Has received treatment with Dopamine or any intravenous vasoactive medication such as Dobutamine, Milrinone, Nitroprusside or intravenous Nitroglycerin for more than 4 hours for the current episode of decompensated CHF or related illness
• Requires an intravenous antiarrhythmic medication during the 48 hours before starting the study