This study aims to compare the acute thrombogenecity and frequency of neoatherosclerotic lesions and other aspects of long term arterial healing such as the frequency of malapposed and uncovered stent struts at 3 years among patients treated with either a biodegradable polymer everolimus-eluting stent (Synergy) or a durable polymer everolimus-eluting stent (Xience Alpine) for STEMI.

DES use has significantly improved clinical outcomes as compared with bare metal stents (BMS), primarily through a notable reduction in the risk of repeat revascularisation. However, durable polymer DES have been associated with an increased risk of late and very late stent thrombosis and the anticipated development of in-stent neoatherosclerosis. In addition, in-vivo study suggest that different types of polymer among current DES might have different responses to acute thrombogenecity after stent implantation.

Patients with STEMI are associated with worse long-term clinical outcomes due to re-infarction and stent thrombosis throughout long-term follow-up. Underlying unstable lesion which includes ruptured plaque and thin-cap fibroatheroma behind stent strut is a predictor of neoatherosclerosis formation.

There is no dedicated randomized trial to comparing biodegradable-polymer versus durable polymer-DES in terms of acute thrombogenecity and long-term healing at 3 years after primary PCI.

Therefore this study is designed to compare the acute thrombogenecity and frequency of neoatherosclerotic lesions and other aspects of long term arterial healing at 3 years among patients treated with either a biodegradable polymer everolimus-eluting stent (Synergy) or a durable polymer everolimus-eluting stent (Xience Alpine) for STEMI.

Inclusion Criteria:

1. Age ≥18 years
2. Primary PCI within 24 hours of symptom onset
3. 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 contiguuoius anterior leads
4. Presence of at least one acute infarct artery target vessel with one or more coronary artery stenoses in a native coronary artery from 2.25 to 4.5 mm in diameter that can be covered with one or multiple stents

Exclusion Criteria:

1. Female ofchildbearing potential (age < 50 years and last menstruation within the last 12 months), who did not undergo tubal ligation, ovariectomy or hysterectomy.
2. Known intolerance to aspirin, clopidogrel, prasugrel, ticagrelor, heparin, stainless steel, cobalt chromium, platinum chromium, everolimus or contrast material
3. Inability to understand and provide informed consent
4. Currently participating in another trial before reaching first endpoint
5. Mechanical complications of acute myocardial infarction
6. Acute myocardial infarction secondary to stent thrombosis or restenosis
7. Planned surgery within 6 months of PCI unless dual antiplatelet therapy is maintained throughout the peri-surgical period
8. Noncardiac comorbid conditions are present with life expectancy <3years or that may result in protocol noncompliance
9. History of bleeding diathesis or known coagulopathy
10. Use of oral anticoagulation
11. Age >90 years
12. LV-function at index procedure <=20%
13. Cancer under active treatment (chemotherapy)
14. Hemodynamic instability following primary PCI
15. Chronic kidey disease (Creatinine - Clearance < 30ml/min)
16. OCT technically not feasible (severe calcification, tortuosity)