• Major Adverse Cardiac and Cerebrovascular Events [ Time Frame: 6 months ]
  The number of major cardiac and cerebrovascular events reported.
• Change in left ventricular filling pressures during volume loading [ Time Frame: baseline, 6 months ]
  The number of subjects to demonstrate an increase in pulmonary capillary wedge pressure in response to volume loading after pericardiotomy vs. prior to pericardiotomy.

• Change in Quality of Life [ Time Frame: baseline, 6 months ]
  Measured using Kansas City Cardiomyopathy Questionnaire (KCCQ)
• Change in exercise capacity [ Time Frame: baseline, 6 months ]
  Measured by Cardiopulmonary Exercise Testing

Inclusion Criteria

• Age ≥ 30 years
• Symptoms of severe dyspnea (III-IV) without evidence of a non-cardiac or ischemic explanation for dyspnea
• EF of > or = 50% determined on most recent imaging study within the preceding 5 years, with no change in clinical status suggesting potential for deterioration in systolic function

• One of the following:

  • Previous hospitalization for HF with radiographic evidence (pulmonary venous hypertension, vascular congestion, interstitial edema, pleural effusion) of pulmonary congestion or
  • Catheterization documented elevated filling pressures at rest (PCWP ≥15 or LVEDP ≥18) or with exercise (PCWP ≥25) or
  • Elevated NT-proBNP (>400 pg/ml) or BNP(>200 pg/ml) or
  • Echo evidence of diastolic dysfunction/elevated filling pressures manifest by medial E/e' ratio≥15 and/or left atrial enlargement and chronic treatment with a diuretic for signs or symptoms of heart failure

• Heart failure is primary factor limiting activity as indicated by answering # 2 to the following question: My ability to be active is most limited by:

  • Joint, foot, leg, hip or back pain
  • Shortness of breath and/or fatigue and/or chest pain
  • Unsteadiness or dizziness
  • Lifestyle, weather, or I just don't like to be active
  • Ambulatory (not wheelchair / scooter dependent)

Exclusion Criteria

• Recent (< 1 month) hospitalization for heart failure
• Left or right ventricular dilatation noted on cardiac imaging study prior to enrollment (either echocardiography or MRI).
• Any hemoglobin (Hgb) < 8.0 g/dl within 30 days prior to randomization
• Any GFR < 20 ml/min/1.73 m2 within 30 days prior to randomization
• Significant alternative cause of dyspnea such as severe chronic obstructive pulmonary disease that is a primary contributor to symptoms in the opinion of the investigator
• Ischemia thought to contribute to dyspnea in the opinion of the investigator
• Acute coronary syndrome within 3 months defined by electrocardiographic (ECG) changes and biomarkers of myocardial necrosis (e.g., troponin) in an appropriate clinical setting (chest discomfort or anginal equivalent)
• PCI, coronary artery bypass grafting, or new biventricular pacing within past 3 months
• Obstructive hypertrophic cardiomyopathy
• Known infiltrative cardiomyopathy (amyloid)
• Pericardial disease (constriction, pericarditis, tamponade)
• Active myocarditis
• Complex congenital heart disease
• Active collagen vascular disease
• Significant valvular heart disease (greater than mild stenosis or greater than moderate regurgitant lesions)
• Acute or chronic severe liver disease as evidenced by any of the following: encephalopathy, variceal bleeding, INR > 1.7 in the absence of anticoagulation treatment
• Terminal illness (other than HF) with expected survival of less than 1 year
• Enrollment or planned enrollment in another therapeutic clinical trial in next 3 months.
• Inability to comply with planned study procedures
• Pregnancy or breastfeeding mothers