CLINICAL TRIAL / NCT02600234

Key Inclusion Criteria: * Chronic symptomatic Heart Failure * Ongoing stable GDMT HF management and management of potential comorbidities * Age ≥ 40 years old * LV ejection fraction ≥ 40% within the past 3 months, without previously documented ejection fraction \<30%. * Elevated left atrial pressure with a gradient compared to right atrial pressure (RAP) documented by end-expiratory PCWP during supine ergometer exercise ≥ 25mm Hg, and greater than RAP by ≥ 5 mm Hg Key Exclusion Criteria: * MI and/or percutaneous cardiac intervention within past 3 months; CABG in past 3 months, or current indication for coronary revascularization * Cardiac Resynchronization Therapy initiated within the past 6 months * Severe heart failure * Inability to perform 6 minute walk test (distance \< 50 m), OR 6 minute walk test \> 600m * History of stroke, transient ischemic attack (TIA), deep vein thrombosis (DVT), or pulmonary emboli within the past 6 months * Presence of significant valve disease * Known clinically significant untreated carotid artery stenosis * Currently requiring dialysis; or estimated-GFR \<25ml/min/1.73 m2 by CKD-Epi equation