Inclusion Criteria:  Adults age 18 years of age or greater; Clinically stable, ambulatory outpatients with HVAD who are fully recovered from surgical implantation.  Exclusion Criteria:  Confirmed or suspected device malfunction (e.g. pump thrombus, LVAD-related infection); Clinical instability, defined as hypotension (mean arterial pressure < 60mmHg and symptomatic, as measured in the advanced heart failure LVAD clinic), or hypertension (mean arterial pressure > 90mmHg); patients with refractory heart failure symptoms with New York Heart Association functional classification IIIB or IV symptoms; any chronic illness which would render the patient unable to complete the protocol as described, including but not limited to: moderate-severe osteoarthritis, severe pulmonary disease requiring supplemental oxygen, uncontrolled hypertension, a high baseline HVAD pump speed above 2860RPM (exercise protocol requires increasing pump speed by up to 240 RPM); chronic kidney disease with a glomerular filtration rate < 30ml/min/1.73m2; absence of a pacemaker-defibrillator (necessary for pacing assessment as described below); individuals with clinical evidence of right ventricular (RV) dysfunction/failure, defined as moderate-severe hypervolemia on physical examination with elevated jugular venous pressure greater than 10cmH20, imaging evidence of severe RV dysfunction by imaging assessment or tricuspid annular plane systolic excursion < 17mmHg, or use of outpatient inotropes for known history of RV dysfunction.