The primary purpose of this study is to determine whether bifurcation stenting guided by on-line three-dimensional optical frequency domain imaging (3D-OFDI) is superior to that with angiographic guidance by measuring incomplete stent apposition (ISA) in the bifurcation segment.

The recently developed optical frequency domain imaging (OFDI) can provide high quality resolution images of the coronary arteries. This new imaging system enhances the understanding of complex coronary lesions and the complex interaction between coronary devices and vessels by assembling/compiling 2-dimensional cross sections.

This 3-dimensional reconstruction with strut segmentation becomes possible on-line in the TERUMO OFDI console with 3-dimensional imaging software, which enables stent enhancement and 3D reconstruction within one minute. This "real time" 3D OFDI will promote the utilisation of 3-dimensional assessment in the treatment of bifurcation lesions.

Inclusion Criteria:

1. Patient is at least 18 years of age and signed Informed Consent
2. Subject has coronary artery disease involving a bifurcation with objective evidence of ischemia including patients with chronic stable angina, silent ischemia and non-ST segment elevation acute coronary syndrome (NSTE-ACS)
3. Subject is appropriate to be treated by PCI according to the local practice (operator's judgment or heart team decision)
4. Patients' residence is in the area covered by the hospital
5. Patients with angiographically significant stenosis (>50 % by visual assessment) in de novo, native, previously unstented bifurcation lesion(s) including left main lesion, which is in operator's opinion appropriate to be treated by PCI with a single stent strategy
6. The size of main vessel matches available Ultimaster stent sizes (<4.0 mm, and 2.0 mm by visual assessment)
7. The size of side branch is >2.0mm in diameter by visual assessment
8. The sidebranch is treatable with a sidebranch fenestration and/or kissing balloon

Exclusion Criteria:

1. Pregnancy
2. Patients with ST elevation myocardial infarction
3. Known intolerance to aspirin, clopidogrel, heparin, cobalt chromium, sirolimus, contrast material
4. Known thrombocytopenia (platelet count< 100,000/mm3)
5. Cardiogenic Shock
6. Significant comorbidities precluding clinical follow-up (as judged by investigators)
7. Major planned surgery that requires discontinuation of dual antiplatelet therapy
8. History of stenting in the target bifurcation lesion
9. Renal insufficiency (GFR/MDRD <45 ml/min), which precludes in operator's opinion contrast injection during repeat OFDI pullback
10. Severely tortuous or angulated coronary anatomy of the study vessel that in the opinion of the investigator would result in sub-optimal optical frequency domain imaging (OFDI) or excessive risk of complication to place an OFDI catheter
11. Target lesion reference vessel diameter (RVD) < 2.25 and > 4 mm
12. Other: Patient is judged inappropriate by the attending physician