Inclusion Criteria:

• 18 years of age or older
• Diagnosis of heart failure requiring hospitalization >1 and ≤12 months prior to screening
• NYHA Class III or IV at the time of screening
• Renal insufficiency as defined by eGFR ≥20 and ≤70 mL/min/1.73 m2
• Negative pregnancy test

Exclusion Criteria:

• History of an allergic reaction to any xanthine-containing compound.
• History of seizure
• History of stroke
• Serious systemic infection
• Sustained systolic blood pressure >170 or <90 mmHg
• Myocardial infarction within 30 days of Day 1
• Hemodynamically destabilizing arrhythmia within 30 days of Day 1
• Uncorrected hemodynamically significant primary valvular disease
• Known obstructive or restrictive cardiomyopathy
• Cardiac surgery within 60 days prior to Day 1
• Likely to undergo cardiac transplantation, device implantation, or other cardiac surgery within next three months
• Evidence of malignancy within 6 months prior to Day 1.
• Participation in any other investigational study of drugs or devices within 30 days prior to Day 1.
• Receiving aminophylline, theophylline or adenosine
• Presence of any clinically significant condition that might interfere with optimal safe participation in this study