The objective of this study is to assess efficacy and safety of Pressure-controlled intermittent Coronary Sinus Occlusion (PiCSO) therapy started post flow restoration but prior to stenting during percutaneous coronary intervention (PCI) compared to standard PCI in the setting of acute ST-segment elevation anterior myocardial infarction (STEMI).

This is a prospective, multicenter, randomized (1:1), controlled, study. Patients with an ST-segment elevated anterior infarct eligible for PCI will be invited to participate in the PiCSO-AMI-I study. After consent as per pproved ethics committee requirements, baseline assessments will be performed. PCI of the culprit vessel should be performed per standard practices. After blood flow restoration, the subjects meeting all inclusion and none exclusion criterial will be enrolled into the study and randomized either to PiCSO Group or Control Group. If the subject is randomized to PiCSO Group, the coronary sinus (CS) will be cannulated through the femoral vein and the PiCSO Impulse Catheter will be placed in the CS. In the event the PiCSO Impulse Catheter cannot be placed in the CS within 30 minutes, the physician should proceed with the regular PCI and the PiCSO treatment will be considered a failure. Once PiCSO Impulse Catheter is placed into CS, PiCSO treatment is started followed by stenting. The physician shall target a PiCSO treatment of 45 minutes (at minimum 30 minutes) whereas the treatment should be continued during and post stent insertion, but should not exceed a maximum duration of 90 minutes. At the end of the PiCSO treatment, the PiCSO Impulse Console is stopped and the PiCSO Impulse Catheter is removed. The patient is seen for a FU visit at 5 days, 30 days, 6 months, 1 year, 2 year and 3 years post index procedure. 5 days and 6 months post index the patient will get a CMR scan. At every FU visit safety data and health status will be documented and quality of life questionnaire will be completed.

Inclusion Criteria:

1. Age ≥18 years old
2. Culprit lesion in proximal or mid LAD
3. Pre-PCI TIMI flow 0 or 1.
4. Symptoms onset time consistent with myocardial ischemia (e.g. persistent chest pain, shortness of breath, nausea/vomiting, fatigue, palpitations or syncope) ≤ 12 h.
5. ECG evidence of acute anterior myocardial infarction with ST-elevation ≥ 2 mm (0.2 mV) in 2 or more contiguous anterior precordial ECG leads (one of which should be V2, V3, or V4) in men or ≥ 1.5 mm (0.15 mV) in women
6. Patient is deemed eligible for primary PCI
7. STEMI patients: consent as per approved national ethical committee specific requirements prior to the procedure.

Exclusion criteria:

1. Implants or foreign bodies in the coronary sinus
2. Known allergy to polyurethanes, PET or stainless steel
3. Known pregnancy and breastfeeding
4. Pericardial effusion (cardiac tamponade)
5. Central hemodynamically relevant left/right shunt
6. Previous MI or CABG
7. History of stroke, TIA or reversible ischemic neurological deficit within last 6 months
8. Known coagulopathy
9. Need for circulatory support or pre-procedural ventilation
10. Patients with cardio-pulmonary resuscitated (CPR) cardiac arrest for more than 5 minutes
11. Patient not suitable for femoral vein access
12. Contraindication to cardiac magnetic resonance imaging (CMR), e.g. claustrophobia, foreign body implants incompatible with CMR, gadolinium intolerance.
13. Active participation in another drug or device investigational study
14. Known severe kidney disease or on hemodialysis
15. Unconscious on presentation
16. Patients under judicial protection, legal guardianship or curatorship

Analysis of the primary endpoint, infarct size 5-days post MI assessed by CMR, will be analyzed by an independent Corelab, blinded to the allocated treatment arm.