The aim of the trial is to assess coronary artery reactivity using adenosine-induced coronary flow reserve (CFR) by transthoracic echocardiography in patients with Bio-active stent (BAS) and Everolimus-eluting stent (EES) distal to the original culprit lesion at 6-8 months.

Objective: The aim of the trial is to assess coronary artery reactivity using adenosine-induced coronary flow reserve (CFR) by transthoracic echocardiography in patients with Bio-active stent (BAS) and Everolimus-eluting stent (EES) distal to the original culprit lesion at 6-8 months.

Design: BASE-CFR is a substudy of the larger randomized multicenter BASE-ACS trial comparing bio-active Titan stent to everolimus-eluting stent in patients with acute coronary syndrome. CFR assessment will be performed at 6-8 months after stent implantation at the same time with OCT assessment. In-stent restenosis will be ruled out using OCT.

Primary endpoint: CFR at 6-8 months after stent implantation.

Secondary endpoint: Coronary flow velocity at baseline and during adenosine-induced hyperemia 6-8 months after stent implantation..

Association of CFR to unendotheliazed stent struts and stent malapposition.

Enrollment: 40 patients (20 receiving BAS and 20 receiving EES).

Clinical site: Satakunta Central Hospital, Finland Turku University Hospital, Finland

Inclusion Criteria:

• The patient is enrolled to the BASE-ACS trial. Treated culprit lesion is in the proximal or middle LAD
• Patient or the patient's legal representative has been informed of the nature of the study and has provided written informed consent as approved by the Institutional Ethics Committee of the respective clinical site

Exclusion Criteria:

• Diabetes mellitus
• Treated stent position other than LAD proximal or middle.
• EF<30%
• Bifurcation lesions
• Renal impairment (creatinine >120 mmol/L)
• No suitable anatomy for OCT scan or CFR measurement

Patients with acute coronary syndrome who were treated with BAS or EES during index PCI.