The purpose is to investigate if a strategy of routine OCT based diagnosis and guidance of PCI improves clinical outcomes compared with a standard strategy of guidance by angiography in patients presenting with ACS

Patients presenting with acute coronary syndrome (ACS) have worse short and mid-term prognosis compared with patients revascularized for chronic coronary syndrome. Angiographic assessment of patients with ACS is frequently limited by high ambiguity both in identification of culprit lesions, characterization of non-culprit lesions, and in identification of suboptimal treatment results. Intravascular imaging may improve diagnosis and allow for better treatment optimization during coronary intervention of patients with ACS. The large-scale Chinese IVUS-ACS trial showed a 50% reduction in one-year MACE with IVUS-guided PCI in patients with ACS whereas a number of small studies on routine OCT guiding as well as ACS subgroups in RCTs did not indicate a potential similar benefit with OCT. OCT assessment has several theoretical advantages over IVUS in patients with ACS indicating the need for a well-designed strategy trial on OCT vs angiographic guided PCI.

Hypothesis: Routine OCT-guided diagnosis and revascularization yields superior one-year clinical outcome compared with standard angiography-guided diagnosis and revascularization in patients with acute coronary syndrome Methods: Investigator initiated, open label, prospective, 1:1 randomized, multi-center, clinical outcome, superiority trial.

Primary Endpoint: Major adverse cardiac events (MACE) comprising all-cause death, spontaneous myocardial infarction and stroke.

Inclusion Criteria:

Clinical inclusion criteria:

• NSTEMI, STEMI
• Symptom duration <12h for STEMI and <48h for NSTEMI
• Age ≥ 18yrs
• Ability to provide written informed consent

Angiographic inclusion criteria:

• Angiographic signs of at least one possible culprit lesion. Signs including acute occlusion, partial occlusion, proximal embolus, haziness, high grade stenosis, stent thrombosis
• Wire in true distal lumen

Exclusion Criteria:

Clinical exclusion criteria

• Intravascular imaging evaluation of any lesions at index procedure
• Cardiogenic shock
• Sustained ventricular tachycardia or ventricular fibrillation
• Planned CABG
• Life expectancy <1 year
• Known severe heart failure with NYHA class equal or above III
• Known ejection fraction <30% before the admission
• Known renal failure with GFR <30 ml/min/1.73 m2
• Active bleeding or coagulopathy
• Relevant allergies (contrast media, aspirin, clopidogrel, ticagrelor, everolimus)
• Suspected inability to lie flat for the duration of the PCI procedure
• Inability to comply with the planned follow-up program
• Known or anticipated compliance problems with medical therapy

Angiographic exclusion criteria

• Study lesion involving the Left main coronary artery
• Study lesion involving a true bifurcation lesion with a SB >2.5mm
• Severe tortuosity
• Distal embolus
• Isolated coronary artery spasm
• Suspected spontaneous coronary artery dissection
• Chronic total occlusions with treatment indication and no antegrade intra plaque wire pass

Limited and pseudo-anonymized data will be transferred to studies investigating the effect of OCT treatment across other studies, so-called meta-analyses. These meta-analyses will be carried out with Rigshospitalet (Copenhagen, Denmark) and the Cardiovascular Research Foundation (New York, USA). Full anonymization means that the information cannot be linked to individuals. The studies to which data are transferred comply with the General Data Protection Regulation and the Danish Data Protection Act. Data from this study will also be transferred to a project at Aarhus University investigating prognosis across patient groups treated with OCT.