This is an observational study of the functional capacity of patients with Heart failure with Reduced Ejection Fraction (HFrEF) who are admitted to the hospital for routine medical treatment.

This observational study will evaluate the functional capacity (ability to walk and distance walked) of patients with Heart failure with Reduced Ejection Fraction (HFrEF) in approximately 50-70 patients who present with Acute Heart Failure to approximately 5-6 hospital sites in the USA. All enrolled patients will be evaluated for their baseline functional capacity. Patients will receive standard Acute Heart Failure therapy and will be serially assessed for change in their functional capacity.

Inclusion Criteria:

• Have a left ventricular ejection fraction (LVEF) ≤40%, as assessed by any method, e.g., echocardiography, a multigated acquisition (MUGA) scan or magnetic resonance imaging (MRI);
• Present with signs and symptoms considered to be primarily due to AHF and be admitted to the hospital for AHF;
• Confirmation verbally that the patient was ambulatory, i.e., able to walk >30m, prior to developing symptoms of AHF leading to the current admission;
• Be capable of understanding the nature of the trial; be willing and able to comply with the inpatient and outpatient study protocol requirements for the duration of the study; and be willing to participate, as documented by written informed consent.

Exclusion Criteria:

• Have a systolic blood pressure <90mmHg or >170mmHg at baseline;
• Have an anticipated need for an invasive procedure within 3 days of study enrollment, e.g., due to hemodynamic or cardiac rhythm instability, or acute coronary syndrome, requiring procedures including, but not limited to, cardiac catheterization, placement of a defibrillator/pacemaker, or placement of a pulmonary artery catheter;
• Have a primary HF etiology attributable to either restrictive/obstructive cardiomyopathy, idiopathic hypertrophic cardiomyopathy (as defined by any wall thickness > 1.8cm) that is obstructive, or uncorrected severe valvular disease (except mitral regurgitation);
• Have any other comorbidities that limit ambulation more than the patient's heart failure, e.g., symptomatic peripheral arterial disease, COPD, arthritis or other condition, as confirmed verbally with the patient;
• Have severe renal insufficiency (defined as a GFR <30mL/min/1.73m2 according to the MDRD equation);
• Have an anticipated survival of less than 90 days, for any reason;
• Have received an investigational agent (drug, device or biologic product) within 30 days (or, if longer, 5 half-lives for a drug or biologic agent) prior to study entry, or be planning to receive an investigational agent at any time throughout the full duration of the study until at least Study Day 35;
• Have any other clinically significant laboratory abnormality, medical condition or social circumstance that, in the investigator's opinion, makes it inappropriate for the patient to participate in this clinical trial.