This prospective, single-center post-market-follow-up study aims to fill knowledge gaps by combining advanced cardiac MRI/MRS with systemic mitochondrial assays and exercise testing to characterize the energetic and functional impact of IASD therapy in HFrEF patients.

All patients receive standard of care percutaneous implantation of the interatrial Ventura shunt according to the instructions for use. Cardiac function, volumes, pressures, and energy efficiency will be determined by state-of-the-art clinical multiparametric cMRI and spectroscopy (MRS) at baseline, 3-months, and 12-months follow-up. Systemic mitochondrial respiratory function will be determined by established Oroboros and Seahorse protocols.

Post-procedural assessments include:

• Cardiac Imaging: Multiparametric cardiac MRI (cMRI) and Phosphorus-31 Magnetic Resonance Spectroscopy (³¹P-MRS) at rest and during cycle ergometry to evaluate ventricular volumes, pressures, and myocardial energy efficiency.
• Functional Testing: Cardiopulmonary exercise testing (CPET) to quantify functional capacity via VO2 max and standardized symptom assessment in the heart failure unit.
• Laboratory & Biomarkers: Blood sampling for systemic mitochondrial respiratory function (PBMC respirometry via Oroboros® and Seahorse® protocols) and serum metabolomic testing.
• Clinical Follow-up: NYHA classification, quality of life assessment using the Kansas City Cardiomyopathy Questionnaire (KCCQ), and standard-of-care echocardiography.

Inclusion Criteria:

1. Ischemic or non-ischemic cardiomyopathy with LVEF ≤ 40%
2. Patient is eligible and scheduled to receive the Ventura IASD as per the current IFU.
3. Symptoms: NYHA Class III
4. Stability: Chronic heart failure for ≥ 6 months on stable, and at least 3 months on guideline-directed medical therapy (GDMT)
5. Biomarkers: NTproBNP ≥ 1,200 pg/ml
6. Age 18 years or older
7. Subject has signed informed consent form and is willing and able to attend all follow-up visits and is physically capable of performing all tests.

Exclusion Criteria:

1. Hemodynamics: Resting SBP < 90 or > 160 mmHg

2. Severe PH (PASP >70 mmHg, PVR > 4 Wood Units)

3. Anatomy/Structure:

   • intracardiac thrombus
   • Severe RV dysfunction (TAPSE <12 mm or RVFAC ≤25%)
   • LVEDD > 8 cm
   • Significant ASD or PFO

4. Valvular Disease:

   • Severe, untreated mitral stenosis or aortic stenosis or regurgitation
   • Mitral repair device <3 months prior to enrollment

5. Recent Events:

   • ACS, PCI, Cardiac Surgery (< 3 months prior to enrollment)
   • CAD requiring revascularization
   • Stroke, TIA, PE, Thrombosis (< 6 months prior to enrollment)

6. Issues undergoing MRI: e.g non-compatible implant, claustrophobia, or physically not suitable for MRI

7. Participation in the active treatment or follow-up phase of another clinical study of an investigational drug or device that has not reached its primary endpoint

8. Any medical or psychiatric condition such as dementia, alcoholism or substance abuse which may preclude informed consent or interfere with any of the study procedures, including follow-up visits

9. Any non-cardiac condition with life expectancy <1 years (e.g., cirrhosis, cancer not in remission, etc.)

10. Subject belongs to a vulnerable population