A total of 50 patients with ST-elevation myocardial infarction (STEMI) undergoing primary-percutaneous coronary intervention (PPCI) will be randomized to two different coronary stents: BIOFREEDOM vs. COMBO stent.

All patients will undergo to 6-month scheduled coronary angiography to evaluate the endothelial function response of the distal coronary segment and other functional parameters.

The bioengineered COMBO stent (Orbus Neich, Fort Lauderdale, Florida, United States) has a dual-therapy strategy, which combines a sirolimus-eluting coating with an anti-CD34 antibody layer to promote vessel healing. Sirolimus release (5 μg/mm) is completed in 30 days, and the biodegradable polymer disappears within 90 days.

CD34 antibodies are immobilized on the surface of the stent and capture circulating endothelial progenitor cells (EPCs). The captured EPCs are triggered by sheer stress from the circulating blood and other cell signals to differentiate and mature into endothelial cells. COMBO Plus is the only stent with a biological coating that actively repairs the vessel morphology. However, little is known regarding the endothelial function after stent implantation.

Inclusion Criteria:

• STEMI < 12 hours undergoing primary PCI.
• ST-segment elevation of > 1mm in > 2 contiguous leads, or (presumably new) left bundle branch block, or true posterior MI with ST depression of >1mm in >2 contiguous anterior leads.
• Presence of at least one acute infarct artery target vessel with one or more de-novo coronary artery stenosis in a native coronary artery within 2.75 - 3.75 mm reference vessel diameter and < 24 mm length (visually estimated).

Exclusion Criteria:

• Inability to provide informed consent
• Female of childbearing potential (age <50 years and last menstruation within the last 12 months), who did not undergo tubal ligation, ovariectomy or hysterectomy
• Known intolerance to aspirin, heparin, PLLA, everolimus, contrast material
• Cardiogenic Shock
• Unprotected left main coronary artery stenosis
• Distal occlusion of target vessel
• Acute myocardial infarction secondary to stent thrombosis
• Mechanical complications of acute myocardial infarction
• Severe tortuous, calcified or angulated coronary anatomy of the study vessel that in the opinion of the investigator would result in sub-optimal imaging or excessive risk of complication in the follow-up procedure
• Active bleeding or coagulopathy or patients at chronic anticoagulation therapy
• Chronic renal dysfunction with creatinine clearance < 45 ml/minm2
• Subject is currently participating in another clinical trial that has not yet completed its primary endpoint