Inclusion Criteria:
1. Diagnostic Criteria
Diagnosis of chronic heart failure according to the Chinese Guidelines for the Diagnosis and Management of Heart Failure (2024), and meeting the following conditions:
1.1 Left Ventricular Ejection Fraction (LVEF) ≤ 40% (HFrEF group). 1.2 Presence of chronic HF symptoms (NYHA functional class II-IV) or objective evidence (e.g., elevated natriuretic peptides, structural cardiac abnormalities).
1.3 Disease duration ≥ 3 months, with no adjustments to the foundational anti-heart failure regimen within the past month.
2. Age and Informed Consent 2.1 Aged 18 to 70 years (inclusive). 2.2 Understand the study purpose and provide signed informed consent.
3. Treatment Stability 3.1 Received guideline-recommended, standardized "New Four Pillars" anti-heart failure therapy (ARNI/ACEI/ARB + β-blocker + MRA + SGLT2 inhibitor) for at least 2 weeks prior to enrollment, with no changes in the past month.
3.2 No diuretic dose adjustments within the past 5 days and no clinical signs of fluid overload (e.g., weight gain of ≥ 2 kg/week, new-onset pulmonary edema).
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Exclusion Criteria:
* Absolute Contraindications
1. Untreated pneumothorax or pneumomediastinum.
2. Claustrophobia, agitation or inability to cooperate, or conditions unsuitable for HBOT such as angle-closure glaucoma or eustachian tube occlusion.
3. Unstable vital signs.
4. Concurrent intracranial hemorrhage, intracranial mass, malignant tumor, uncontrolled epilepsy, psychiatric disorder, coagulation dysfunction, or other severe uncontrolled comorbidities.
5. Severe pulmonary bullae or emphysema.
6. Active internal bleeding or coagulopathy.
7. Uncontrolled hyperpyrexia (body temperature \>38.0°C).
8. Concurrent use of disulfiram, bleomycin, or cisplatin chemotherapy. Relative Contraindications
9. Uncontrolled hypertension (systolic BP \>160 mmHg or diastolic BP \>100 mmHg).
10. Severe cardiac arrhythmias (e.g., third-degree atrioventricular block without a pacemaker, frequent ventricular tachycardia).
11. Chronic obstructive pulmonary disease (FEV1 \<50% of predicted) or active asthma.
12. Psychiatric or cognitive impairment preventing cooperation with the therapy. Comorbidity Restrictions
13. End-stage renal disease (dialysis-dependent).
14. Terminal malignancy (life expectancy \<6 months).
15. Pregnancy or lactation (a negative pregnancy test is required for women of childbearing potential).
Recent Clinical Events
16. Acute myocardial infarction or unstable angina within the past 4 weeks.
17. Hospitalization or emergency department visit for acute heart failure within the past 2 weeks.
18. Current use of intravenous positive inotropic agents.
19. Within 6 months after cardiac surgery.
20. Use of any mechanical circulatory support.
21. Participants with a 6-minute walk test result exceeding 450 meters or who are unable to complete the test.
Other Exclusion Conditions
22. Inability to complete follow-up (e.g., planned relocation, non-compliance with follow-up assessments).
23. Concurrent participation in any other clinical trial that may interfere with the outcomes of this study.
24. Unforeseen circumstances judged by the investigators to be ineligible.
