Endocalyx for Heart Failure

Inclusion Criteria: 1. Documented or suspected heart failure with reduced ejection fraction (HFrEF and HFmrEF according to ESC guidelines). 2. Signs of congestion, defined as: a. Elevated NT-proBNP levels: i. \>450 pg/ml in subjects aged \<55 years. ii. \>900 pg/ml in subjects aged 55-75 years. iii. \>1800 pg/ml in subjects aged \>75 years. AND b. Use of diuretics, OR c. Presence of peripheral edema, OR d. Complaints of orthopnea or paroxysmal nocturnal dyspnea, OR e. A chest X-rays with sings of volume overload, OR f. Hypertension, as defined by an office blood pressure \>140/90 mmHg. 3. Stable diuretic and antihypertensive treatment for the previous 3 weeks. 4. Subject, or legal representative, has voluntarily signed and dated an Informed Consent Form, approved by an Institutional Review Board (IRB)/Independent Ethics Committee (IEC), after the nature of the study has been explained and the subject has had the opportunity to ask questions. The informed consent must be signed before any study-specific procedures are performed. Rationale for the inclusion criteria: (1-3) To select the adequate subject population with appropriate disease severity for the evaluation. NT-proBNP levels are known to increase with age.(21, 22) The cutoffs of NT-proBNP levels were selected according the 2021 European Society of Cardiology Guidelines for the diagnosis and treatment of acute and chronic heart failure. (23) (4) In accordance with GCP. Should inclusion prove difficult, we will lower required NT-proBNP levels by 25% to respectively 338, 675 and 1350 pg/ml. We will notify the METC of this decision. Exclusion Criteria: 1. Age \<18 years. 2. Estimated glomerular filtration rate (eGFR) \<15 ml/min/1.73m2 measured by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. 3. Systolic (\<105 mmHg) or diastolic hypotension (\<60 mmHg) as measured by office blood pressure measurements. 4. Severe symptoms of (orthostatic) hypotension. 5. An acute coronary syndrome, stroke, transient ischemic attack or cardiovascular surgery in the last 3 months. 6. Hospitalization for heart failure in the past 3 weeks. 7. Dialysis treatment or expected initiation of dialysis within 3 months of screening. 8. Women of child bearing potential. 9. Planned surgery in the next 8 weeks. 10. Major surgery in the previous 4 weeks. 11. Use of any other investigational drug. 12. Presence of significant comorbidities (e.g., advanced malignancy, advanced liver disease) with a life expectancy of less than 1 year. 13. A psychiatric, addictive or any disorder that compromises ability to give truly informed consent for participation in this study. 14. Known hypersensitivity to seaweed, corn, artichoke, grape, melon or to any of the excipients of Endocalyx. 15. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose galactose malabsorption.