This is a multicenter, parallel-group, randomized, open-label, controlled trial. Patients with a diagnosis of acute heart failure (AHF) in the emergency department (ED) or after emergency presentation to hospital will be screened and informed of the study. After signed consent, patients will be randomized into the control group (usual AHF treatment) or intervention group (usual AHF treatment + prednisone). Prednisone will be given for 7 days. Patients will be assessed at days 2, 4 or at discharge if earlier, and at day 7 at hospital visit. If the patient has been discharged before day 7, a follow-up visit will be scheduled at day 7 for endpoints assessment followed by a scheduled hospital visit at day 31 and a telephone follow-up at day 91. Study drug will be dispensed for the patient to take home until day 7.

CORTAHF is a parallel-group, comparative, open-label, randomised (1:1), controlled trial. Patients with a diagnosis of AHF in the ED or after emergency presentation to hospital will be screened and informed of the study. After signed consent, patients will be randomized into the control group (usual AHF treatment) or intervention group (usual AHF treatment + prednisone).

Prednisone will be given for 7 days. Patients will be assessed at days 2, 4 or at discharge if earlier, and at day 7 at hospital visit. If the patient has been discharged before day 7, a follow-up visit will be scheduled at day 7 for endpoints assessment followed by a scheduled hospital visit at day 31 and a telephone follow-up at day 91. Study drug will be dispensed for the patient to take home until day 7.

Inclusion Criteria:

1. Age 18 to 85 years of age
2. Unplanned ED visit or hospital presentation within the 12 hours prior to Screening with acute or worsening dyspnea and/or orthopnea, and pulmonary congestion on chest X-ray or lung ultrasound.
3. All measures from presentation to randomization of systolic blood pressure ≥ 100 mmHg, and of heart rate ≥ 60 bpm.
4. Written informed consent to participate in the study.
5. Biomarker levels indicative of congestion and inflammation: At Screening, NT-proBNP > 1,500 pg/mL and CRP > 20 mg/L
6. Patient agrees for follow-up visits at the hospital at day 7 in case of earlier discharge and Day 31.

Exclusion Criteria:

1. Anticipated life expectancy less than 6 months
2. Mechanical ventilation (not including CPAP/BIPAP) prior to Screening.
3. Significant pulmonary disease contributing substantially to the patients' dyspnea such as FEV1< 1 liter or need for chronic systemic or non-systemic steroid therapy, or any kind of primary right heart failure such as primary pulmonary hypertension or recurrent pulmonary embolism.
4. Myocardial infarction, unstable angina or cardiac surgery within 3 months, or cardiac resynchronization therapy (CRT) device implantation within 3 months, or percutaneous transluminal coronary intervention (PTCI), within 1 month prior to inclusion.
5. Index Event (admission for AHF) triggered primarily by a correctable etiology such as significant arrhythmia (e.g., sustained ventricular tachycardia, or atrial fibrillation/flutter with sustained ventricular response >130 beats per minute, or bradycardia with sustained ventricular arrhythmia <45 beats per minute), infection, severe anemia, acute coronary syndrome, pulmonary embolism, exacerbation of COPD, planned admission for device implantation or severe non-adherence leading to very significant fluid accumulation prior to admission and brisk diuresis after admission. Troponin elevations without other evidence of an acute coronary syndrome are not an exclusion.
6. Uncorrected thyroid disease, active myocarditis, or known amyloid or hypertrophic obstructive cardiomyopathy.
7. History of heart transplant or on a transplant list, or using or planned to be implanted with a ventricular assist device.
8. Sustained ventricular arrhythmia with syncopal episodes within the 3 months prior to screening that is untreated.
9. Presence at screening of any hemodynamically significant valvular stenosis or regurgitation, except mitral or tricuspid regurgitation secondary to left ventricular dilatation, or the presence of any hemodynamically significant obstructive lesion of the left ventricular outflow tract.
10. Primary liver disease considered to be life threatening
11. Renal disease or eGFR < 30 or > 80 mL/min/1.73m2 (as estimated by the simplified MDRD formula) at inclusion or history of dialysis.
12. Systemic steroid therapy, within 30 days from inclusion.
13. Inability to consent, or patient under guardianship measure
14. Participation in another intervention trial in the past 30 days
15. Anticipated non-adherence to study protocol or follow-up.
16. Pregnant or nursing (lactating) women.
17. Known hypersensitivity to steroids or constituents of prednisone tablets (excipients)
18. Psychotic states not yet controlled by treatment
19. Concomitant administration of live vaccines and up to 3 months after end of corticotherapy administration.
20. Patient under legal protection measure (tutorship or curatorship) and patient deprived of freedom
21. Persons subject to psychiatric care without their consent