Evaluation of an Implant Free Interatrial Shunt to Improve Heart Failure

Key Inclusion Criteria: * Documented chronic, symptomatic heart failure and NYHA Class II, Class III or ambulatory Class IV at the time of screening visit and receiving guideline directed medical therapy. * At least one hospitalization or emergency department visit with heart failure as the primary or secondary diagnosis or intravenous diuretic treatment for heart failure or documentation of elevated BNP. * LVEF ≥ 40%. * Echocardiographic evidence of diastolic dysfunction during the baseline echocardiography: * Per baseline exercise right heart catheterization, site measured elevated left atrial pressure with a gradient compared to right atrial pressure. Key Exclusion Criteria: * Stroke or thromboembolic event in the past 6 months. * Severe or advanced heart failure such as Stage D heart failure, non-ambulatory NYHA Class IV, cardiac index less than 2.0 L/min/m2, LVEDD \> 6 cm, or received inotropic therapy for LVEF less than 40% within 6 months prior to enrollment. * Any of the following within 3 months prior to enrollment: myocardial infarction, percutaneous cardiac intervention, CABG, cardiac resynchronization therapy, AICD, or indicated for coronary revascularization at the time of enrollment. * More than moderate valve disease (mitral, tricuspid, aortic) at the time of enrollment. * Chronic pulmonary disease requiring continuous home oxygen or hospitalization within prior 12 months for pulmonary disease. * BMI \> 40. * 6-minute Walk Test distance less than 100 m or greater than 450 m performed during baseline screening, or unable to perform baseline bicycle exercise test. * Any of the following at the time of baseline screening: moderate or worse right heart dysfunction, requires dialysis, atrial fibrillation with ventricular rate \> 100 bpm, systolic blood pressure greater than 170 mmHg (average of 3 measurements at baseline). * Evidence of precapillary pulmonary hypertension defined as PVR \> 2 Wood units at rest, TPG \> 15 at rest or with exercise, resting RA \> 15 mmHg, or RA to PCWP ratio \> 0.7 at rest and with exercise. * Anatomic anomaly that precludes creation of interatrial shunt.