(all must be present) 1. Subject must be at least 18 years of age. 2. Subject must have evidence of myocardial ischemia (e.g., stable angina, silent ischemia (ischemia in the absence of chest pain or other anginal equivalents), unstable angina, or acute myocardial infarction) suitable for elective PCI. 3. Patients undergoing planned XIENCE stent implantation during a clinically indicated PCI procedure meeting one or more of the following criteria: A) High clinical-risk, defined as; i. Medication-treated diabetes mellitus, AND/OR B) High angiographic-risk lesion(s), with at least one target lesion in each target vessel planned for randomization meeting at least one of the following criteria; i. Target lesion is the culprit lesion responsible for either: - NSTEMI, defined as a clinical syndrome consistent with an acute coronary syndrome and a minimum troponin of 1 ng/dL (may or may not have returned to normal), OR - STEMI >24 hours from the onset of ischemic symptoms ii. long or multiple lesions (defined as intended total stent length in any single target vessel ≥28 mm), Note: For a long target lesion, this would permit treatment by a single long stent or overlapping stents. Note: For up to two target lesions located in a single target vessel and treated with non-overlapping stents, they may be located in a continuous vessel or split up between a main vessel and a side branch. iii. bifurcation intended to be treated with 2 planned stents (i.e. in both the main branch and side branch), and where the planned side branch stent is ≥ 2.5 mm in diameter by angiographic visual estimation. iv. angiographic severe calcification (defined as angiographically visible calcification on both sides of the vessel wall in the absence of cardiac motion), v. chronic total occlusion (CTO) (enrolment and randomization in this case performed only after successful antegrade wire escalation crossing and pre-dilatation) vi. in-stent restenosis of diffuse or multi-focal pattern. Lesion must be at or within the existing stent margin(s) and have angiographically visually-assessed DS ≥70% or DS ≥50% with non-invasive or invasive evidence of ischemia 4. All target lesions (those lesions to be randomized) must have a visually estimated or quantitatively assessed %DS of either ≥70%, or ≥50% plus one or more of the following: an abnormal functional test (e.g. fractional flow reserve, stress test) signifying ischemia in the distribution of the target lesion(s) or biomarker positive ACS with plaque disruption or thrombus. Note: For purposes of study eligibility, a minimum troponin of 1 ng/dL at the time of screening will be considered biomarker positive. 5. All target lesions must be planned for treatment with only ≥2.5 mm and ≤3.5 mm stents and post-dilatation balloons based on pre-PCI angiographic visual estimation. 6. No more than 2 target lesions requiring PCI are present in any single vessel., and no more than 2 target vessels are allowed. Thus, up to 4 randomized target lesions per patient in a maximum of 2 target vessels are allowed, including branches. The intended target lesions will be declared just prior to randomization. Note: A lesion is defined as any segment(s) of the coronary tree, no matter how long, which is planned to be covered with one contiguous length of stent, whether single or overlapped. A bifurcation counts as a single lesion even if the side branch is planned to be treated. Note: All lesions in a randomized target vessel that are intended to be treated by PCI are designated as target lesions, and at least one target lesion in each randomized target vessel must meet angiographic high-risk inclusion criteria summarized above in 3B). The only exception is for patients who qualify for the trial on the basis of medication-treated diabetes, in which case no target lesion is required to meet angiographic high-risk inclusion criteria. 7. All target lesions intended to be treated by PCI in the target vessel are amenable to OCT-guided PCI. Example: If a qualifying angiographic high-risk lesion is in the proximal LAD, and there is a second target lesion in the distal LAD which is a focal lesion not otherwise meeting high-risk criteria, both the proximal LAD and distal LAD lesions must be amenable to OCT (e.g. no excessive tortuosity or calcification precluding delivering the OCT catheter), and each lesion must undergo OCT-guided stenting. Otherwise the vessel should be excluded from randomization. 8. Subject must provide written Informed Consent prior to any study related procedure.

(none may be present) Clinical exclusion criteria: 1. STEMI ≤24 hours from the onset of ischemic symptoms 2. Creatinine clearance ≤30 ml/min/1.73 m^2 (as calculated by MDRD formula for estimated GFR) and not on dialysis. Note: chronic dialysis dependent patients are eligible for enrolment regardless of creatinine clearance. 3. Hypotension, shock or need for mechanical support or intravenous vasopressors at the time the patient would be undergoing the index procedure. 4. CHF (Killip class ≥2 or NYHA class ≥3) 5. LVEF ≤30% by the most recent imaging test within 3 months prior to procedure. If no LVEF test result within 3 months is available, it must be assessed by echocardiography, multiple gated acquisition (MUGA), magnetic resonance imaging (MRI), ventriculography (LV gram) or other method. 6. Unstable ventricular arrhythmias 7. Inability to take DAPT (both aspirin and a P2Y12 inhibitor) for at least 12 months in the patient presenting with an ACS, or at least 6 months in the patient presenting with stable CAD, unless the patient is also taking chronic oral anticoagulation in which case a shorter duration of DAPT may be prescribed per local standard of care. 8. Planned major cardiac or non-cardiac surgery within 24 months after the index procedure. Note: Major surgery is any invasive operative procedure in which an extensive resection is performed, e.g. a body cavity is entered, organs are removed, or normal anatomy is altered. Note: Minor surgery is an operation on the superficial structures of the body or a manipulative procedure that does not involve a serious risk. Planned minor surgery is not excluded. 9. Prior PCI within the target vessel within 12 months Note: Prior PCI within the target vessel within 12 months is allowed for in-stent restenosis (target lesion is the prior PCI site) if no more than one layer of previously implanted stent is present. Note: In-stent restenosis involving two or more layers of stent implanted at any time prior to index procedure (i.e. an earlier episode of in-stent restenosis previously treated with a second stent) is excluded. 10. Any planned PCI within the target vessel(s) within 24 months after the study procedure, other than a planned staged intervention in a second randomized target vessel. Note: Planned staged interventions must be noted at the time of randomization, and the decision to stage may be modified within 24 hours of completion of the index PCI. Note: PCI in non-target vessels is permitted >48 hours after the index procedure. 11. Any prior PCI in a non-target vessel within 24 hours before the study procedure, or within previous 30 days if unsuccessful or complicated. Note: Patients requiring non-target vessel PCI may be enrolled and the non-target vessel(s) may be treated in the same index procedure as the randomized lesions (in all cases prior to randomization), as long as treatment of the lesion(s) in the non-target vessel is successful and uncomplicated. Successful and uncomplicated definition for non-target vessel treatment during the index procedure: Angiographic diameter stenosis <10% for all treated non-target lesions, with TIMI III flow in this vessel, without final dissection ≥ NHLBI type B, perforation anytime during the procedure, prolonged chest pain (>5 minutes) or prolonged ST-segment elevation or depression (>5 minutes), or cardiac arrest or need for defibrillation or cardioversion or hypotension/heart failure requiring mechanical or intravenous hemodynamic support or intubation). 12. Subject has known hypersensitivity or contraindication to any of the study drugs (including all P2Y12 inhibitors, one or more components of the study devices, including everolimus, cobalt, chromium, nickel, platinum, tungsten, acrylic and fluoropolymers, or radiocontrast dye) that cannot be adequately pre-medicated. 13. Subject has received a solid organ transplant which is functioning or is active on a waiting list for any solid organ transplants with expected transplantation within 24 months. 14. Subject is receiving immunosuppressant therapy or has known immunosuppressive or severe autoimmune disease that requires chronic immunosuppressive therapy (e.g., human immunodeficiency virus, systemic lupus erythematosus, etc.). Note: corticosteroids are not included as immunosuppressant therapy. 15. Subject has previously received or is scheduled to receive radiotherapy to a coronary artery (vascular brachytherapy), or the chest/mediastinum. 16. Subject has a platelet count <100,000 cells/mm^3 or >700,000 cells/mm^3. 17. Subject has a documented or suspected hepatic disorder as defined as cirrhosis or Child-Pugh ≥ Class B. 18. Subject has a history of bleeding diathesis or coagulopathy, or has had a significant gastro-intestinal or significant urinary bleed within the past six months. 19. Subject has had a cerebrovascular accident or transient ischemic neurological attack (TIA) within the past six months, or any prior intracranial bleed, or any permanent neurologic defect, or any known intracranial pathology (e.g., aneurysm, arteriovenous malformation, etc.). 20. Subject has extensive peripheral vascular disease that precludes safe 6 French sheath insertion. Note: femoral arterial disease does not exclude the patient if radial access may be used. 21. Subject has life expectancy <2 years for any non-cardiac cause. 22. Subject is currently participating in another investigational drug or device clinical study that has not yet completed its primary endpoint. 23. Pregnant or nursing subjects and those who plan pregnancy in the period up to 2 years following index procedure. Female subjects of child-bearing potential must have a negative pregnancy test done within 7 days prior to the index procedure per site standard test. 24. Presence of other anatomic or comorbid conditions, or other medical, social, or psychological conditions that, in the investigator's opinion, could limit the subject's ability to participate in the clinical investigation or to comply with follow-up requirements, or impact the scientific soundness of the clinical investigation results. Angiographic exclusion criteria 1. Syntax score ≥33, unless a formal meeting of the Heart Team, including a cardiac surgeon, concludes that PCI is appropriate. 2. Planned use of any stent <2.5 mm in a target vessel based on visual estimation (note: a smaller stent may be used in a bail-out scenario - e.g. to treat a distal dissection - but its use cannot be planned prior to enrolment) 3. Planned use of a stent or post-dilatation balloon ≥3.75 mm for the target lesion 4. Severe vessel tortuosity or calcification in a target vessel such that it is unlikely that the OCT catheter can be delivered (note: severe vessel calcification is allowed if it is expected that the OCT catheter can be delivered at baseline or after vessel preparation with balloon pre-dilatation or atherectomy) 5. The target vessel has a lesion with DS ≥ 50% that is not planned for treatment at the time of index procedure. 6. The target lesion is in the left main coronary artery 7. The target lesion is in a bypass graft conduit. Note: A native coronary artery may be randomized if a prior bypass graft conduit to the vessel is totally occluded, but not if it is patent. 8. The target lesion is an ostial RCA stenosis 9. The target lesion is a stent thrombosis 10. Planned use of any stent other than Xience in a target lesion