This study will evaluate how the cardiovascular system interacts with mechanical hearts to provide blood flow to the body during exercise. Two aims are proposed: 1) to determine the impact of a mechanical heart on exercise pressor reflexes in heart failure patients; and 2) to define the primary determinant(s) of exercise capacity in heart failure patients before and after device implantation.

Advanced Heart Failure-

Inclusion Criteria:

• Individuals with severely reduced left ventricular systolic function that are scheduled to undergo LVAD insertion

Exclusion Criteria:

• uncontrolled diabetes with peripheral neuropathy (interferes with acquisition of MSNA signal)
• Individuals with clinical right ventricular failure, defined as moderate-severely reduced RV systolic function on echocardiography, or clinical evidence of RV failure (elevated jugular venous pressures, significant peripheral edema)
• Individuals with moderate-severe preexisting aortic insufficiency, as these patients will typically undergo a Park stitch at time of CF-LVAD insertion to permanently close the aortic valve and prevent worsening aortic insufficiency; and
• Disorders that adversely influence exercise ability (e.g. arthritis, peripheral vascular disease, pulmonary disease)

Mild Heart Failure -

Inclusion Criteria:

• Individuals with medically managed left ventricular systolic function that are NOT scheduled to undergo LVAD insertion
• HF patients with ejection fraction <35-40%

Exclusion Criteria:

• Individuals requiring systemic anticoagulation with vitamin-K antagonists or new/direct oral anticoagulants ("NOAC"/"DOAC")
• Disorders that adversely influence exercise ability (e.g. arthritis, peripheral vascular disease, pulmonary disease)
• History of uncontrolled arrhythmias (e.g. ventricular tachycardia or nonsustained ventricular tachycardia).

Healthy Controls -

Inclusion Criteria:

- Persons without a past medical history of cardiovascular disease or related disease (e.g. hypertension, diabetes, peripheral vascular disease, arrhythmias, stroke/transient ischemic attack) and are not taking any cardiac-related medications (e.g. antihypertensive medications)

Exclusion Criteria:

• Individuals requiring systemic anticoagulation with vitamin-K antagonists or new/direct oral anticoagulants ("NOAC"/"DOAC")
• Disorders that adversely influence exercise ability (e.g. arthritis, peripheral ascular disease).

40 - HF patients with advanced heart failure who are scheduled to undergo LVAD insertion (Advanced Heart Failure)

10 - HF patients with mild heart failure who are not scheduled to undergo LVAD insertion, to serve as first control group (Mild Heart Failure)

10 - Age-matched healthy individuals, with no past medical history, to serve as a second control group (Healthy Controls)