Exploratory Study of the Edwards APTURE Transcatheter Shunt System (ALT-FLOW Canada)

Inclusion Criteria: * Symptomatic HF: * NYHA II w/ history of \> II; III; or ambulatory IV AND * ≥1 HF hospitalization OR treatment with IV or oral diuresis within 12 months OR Elevated NT-proBNP value \> 150 pg/ml in normal sinus rhythm, \>450 pg/ml in atrial fibrillation, OR a BNP value \> 50 pg/ml in normal sinus rhythm, \> 150 pg/ml in atrial fibrillation within the past 6 months prior to study entry * On stable GDMT for HF * Left Ventricular Ejection Fraction (LVEF) ≤ 40% as determined by site cardiologist * Hemodynamic criteria o At rest: Elevated LAP (or PCWP) \> 15 mmHg AND LAP \> RAP + 5 mmHg AND/OR supine ergometer exercise: elevated LAP (or PCWP) \> 25 mmHg AND LAP \> RAP + 10 mmHg * Pulmonary Vascular Resistance (PVR) \< 5.0 WU as determined by site cardiologist Exclusion Criteria * Severe HF: * NYHA IV, stage D, non-ambulatory, transplant list * Cardiac index ≤ 1.5 L/min/m2 * Left Ventricular End-Diastolic Diameter (LVEDD) \> 8 cm * LVEF \<20% * Valve disease * MR \>3+ or \> moderate MS, TR \>3+ (severe on 5-point scale), AR \>2+, * OR \> moderate AS * MI or therapeutic invasive cardiac procedure \< 3 months * TIA, stroke, CRT implanted \< 6 months * RV dysfunction \> mild by TTE OR TAPSE \<1.2 OR RV size ≥ LV size by TTE, OR Right Ventricular Fractional Area Change (RVFAC) ≤ 25% * Dialysis OR renal dysfunction (S-Cr \> 220 micromol/L OR e-GFR \< 25ml/min/1.73 m2) * 6MWT \<50m OR \>400m * Active endocarditis or infection \< 3 months * Mean Right Atrial Pressure (mRAP) \> 15 mmHg as determined by site cardiologist * Body Mass Index (BMI) ≥ 45 kg/m2