The purpose of this study is to identify changes in heart tissue structure and biological function in patients with heart failure by performing an endomyocardial biopsy (EMB or heart biopsy) during a right heart catheterization (RHC). The ultimate goal is to use this information to develop new treatments for heart failure.

Inclusion Criteria:

• HFpEF criteria

  1. Age ≥30 years.

  2. Left ventricular ejection fraction ≥50% measured by echocardiography, CMR or MUGA (measured within one year + clinical stability)

  3. Definition of HFpEF: signs and/or symptoms of HF, NYHA functional class II-IV, and at least one of the following:

     1. Elevated BNP (≥75 pg/ml in sinus rhythm or ≥225 pg/ml in atrial fibrillation/flutter) or NTproBNP (≥225 pg/ml in sinus rhythm or ≥675 in atrial fibrillation/flutter) at baseline. Choice of BNP or NTproBNP is based on availability at each clinical center.
     2. Prior HF hospitalization (primary reason for the hospitalization is HF with elevated natriuretic peptide levels [using the thresholds listed above], requiring IV diuresis for HF, or pulmonary edema or pulmonary vascular congestion on chest radiography).
     3. Previously documented elevated pulmonary capillary wedge pressure (PCWP) at rest (≥15 mmHg) or during exercise (≥25 mmHg for supine exercise or PCWP/cardiac output ratio ≥2 mmHg/L/min for upright exercise).
     4. Elevated H2FPEF score69 (≥5) or HFA-PEFF70 score (≥5).

Suspected HFpEF criteria

1. Age ≥30 years.

2. Left ventricular ejection fraction ≥50% measured by echocardiography, CMR or MUGA (measured within one year + clinical stability)

3. Signs and/or symptoms of HF, NYHA functional class II-IV and all of the following:

   1. Does not meet BNP or NT-proBNP criteria for HFpEF (above)
   2. No prior HF hospitalization meeting HF criteria (above)
   3. No previous hemodynamic catheterization documentation of HF (as above)

Exclusion Criteria:

• 1. Inadequate echo or fluoroscopic images.

  2. Neck anatomy unfavorable for jugular venous cannulation

  3. Therapy with direct oral anticoagulants without cessation for a period (age, renal function, and agent specific) deemed adequate to normalize coagulation according to local clinical guidelines.

  4. Previous or ongoing therapy with warfarin with INR ≥ 1.6 measured day before or of EMB

  5. Platelet count < 50,000/ml

  6. Active bleeding or coagulation disorder

  7. Infection or fever

  8. Endocarditis

  9. Pregnancy

  10. Intracardiac thrombus

  11. RV Aneurysm

  12. Clinically significant tricuspid, pulmonary or aortic valve stenosis

  13. Tricuspid or pulmonary mechanical valve prosthesis

  14. Left bundle branch block

Adults over 30 years of age.