The goal of this clinical trial is to demonstrate the improvement in Coronary Microcirculation Dysfunction (CMD) with Super Saturated Oxygene (SSO2) therapy in patients with anterior ST-segment Elevation Myocardial Infarction (STEMI) successfully revascularized by percutaneous coronary intervention (PCI).

Participants will receive SSO2 therapy for 60 minutes, which aims to overoxygenate their blood. Improvement in CMD will be assessed by comparing angio-IMR before and after 60 minutes of SSO2 therapy measured on conventional angiographic images.

Ten patients with acute anterior STEMI undergoing primary PCI will be enrolled. After successful PCI of a proximal lesion or middle left anterior descending artery (LAD), the patient will be informed and emergency consent will be obtained.

SSO2 therapy will then be performed. Blood is drawn from a femoral artery sheath and circulated via a roller pump through an extracorporeal oxygenator located in a polycarbonate chamber to achieve a PaO2 of 760 to 1000 mmHg. The overoxygenated blood is then delivered to the origin of the LAD at a flow rate of 100 ml/min for 60 minutes via a dedicated catheter.

Improvement in CMD will be assessed by comparing angio-IMR before and after 60 minutes of SSO2 therapy measured on conventional angiographic images. Then, conventional follow-up of previous STEMI will be performed by imaging and functional assessment.

The primary endpoint will be analyzed using a paired Student's t test, to take into account the evolution "before/after" implementation of SSO2 therapy on CMD.

The demonstration of the beneficial effect of SSO2 therapy on CMD will allow the development of a care strategy based on CMD measurement by angio-IMR. Thus, this new treatment could be reserved for patients with severe CMD for which our management arsenal is still lacking, even though we know that CMD is a major prognostic factor in STEMI patients.

Inclusion Criteria:

• Age >18 years and <80 years
• ST-segment elevation myocardial infarction within 6 hours of symptom onset with ≥1 mm ST-segment elevation in ≥2 contiguous leads in V1-V4 or new left bundle branch block.
• Successful PCI of a proximal or medial LAD lesion with commercially available coronary stents and achievement of residual stenosis <50% diameter and thrombolysis-in-myocardial-infarction (TIMI) flow grade 2 or 3.
• Systemic arterial pO2 greater than or equal to 10.7 kPa or 80 mmHg with or without oxygen supplementation.
• Patient enrolled in a social security plan or beneficiary of such a plan
• Consent obtained from the patient before inclusion (Emergency consent)

Exclusion Criteria:

• History of anterior coronary artery bypass grafting (CABG)
• Previous myocardial infarction
• History of PCI on the LAD
• New LAD PCI planned within 30 days.
• Mechanical complications of STEMI (Patients with ventricular pseudoaneurysm, ventricular septal defect (VSD), or severe mitral valve regurgitation (with or without papillary muscle rupture)), cardiogenic shock, or Presence of an intra-aortic counterpulsation balloon.
• Valvular stenosis or heart failure, pericardial disease, or nonischemic cardiomyopathy.
• Known prior left ventricular ejection fraction (LVEF) < 40%,
• Use of thrombolytic therapy
• Patients with a contraindication to anticoagulant therapy.
• Creatinine clearance <30 ml/min/1.73 m2,
• Hemoglobin <10 g/dL
• Gastrointestinal or urogenital bleeding within the last two months or any major surgery (including CABG) within six weeks prior to surgery.
• Female of childbearing age
• Patient on deferral or participating in another clinical investigation,
• Protected populations: pregnant women, parturients, nursing mothers; persons deprived of liberty by a judicial or administrative decision; protected adults