- Receiving heart failure (HF) treatment, including, but not limited to, angiotensin converting enzyme inhibitors (ACEI) and/or angiotensin receptor blockers (ARB), and an evidence-based beta blocker for the treatment of HF. Subjects who cannot tolerate ACEI or ARB due to reduced renal function or hypotension are eligible. Subjects may be receiving aldosterone antagonists, but this is not a requirement for the study.