Investigator-initiated, international, multicentre, observational study with two cohorts.

The two study cohorts will be:

Cohort A: to understand if the local blood flow patterns (associated with low WSS), as evaluated by computational fluid dynamic tools from combined angiographic and OCT invasive images, may better predict the clinical outcome of patients with bifurcated coronary lesions treated by PCI.

Cohort B: to understand if the local blood flow patterns (associated with low WSS), as evaluated by computational fluid dynamic tools from combined angiographic and OCT invasive images, may better predict the clinical outcome of patients with sub-critical bifurcated lesions managed conservatively.

Coronary angiography and OCT images will be combined to obtain a three-dimensional model of the diseased coronary vessels that will be used to calculate the local blood flow patterns and the time-averaged WSS at the bifurcated lesion level by using computational fluid dynamics software.

Baseline (in patients both managed conservatively and treated by PCI) and post-PCI (in patients treated by PCI) images will be processed.

Inclusion Criteria

• Patients with stable or unstable coronary artery disease;
• TIMI 3 on both MV and SB;
• MV visual diameter > 2.5 mm;
• SB visual diameter > 2.0 mm;
• Documentation of angiographically-critical (visually estimated percentage diameter stenosis ≥80% <100%) coronary lesion treated by PCI and underwent post-PCI OCT assessment or angiographically-intermediate (visually estimated percentage diameter stenosis ranging between 30-80%) lesion in the MV considered suitable for conservative management (myocardial revascularization not planned).

Exclusion Criteria

• Age < 18 years or impossibility to give informed consent.
• Female sex with child-bearing potential.
• Life expectancy of less than 12 months or factors making clinical follow-up difficult (no fixed address, etc.).
• Ascertained or suspected contraindications to prolonged (up to 6 month) double antiplatelet therapy.
• Known hypersensitivity to aspirin, heparin, contrast dye, sirolimus, everolimus, zotarolimus, cobalt, chromium, nickel, tungsten acrylic, and fluoro-polymers.
• Poor cardiac function as defined by left ventricular global ejection fraction ≤ 30%.
• Recent (< 48 hours) ST-segment elevation myocardial infarction.
• Severe myocardial hypertrophy (interventricular septum thickness > 15 mm, ECG Sokolow's criteria fulfilled).
• Severe valvular heart disease.
• Significant platelet count alteration (<100,000 cells/mm3 or > 700,000 cells/mm3).
• Gastrointestinal bleeding requiring surgery or blood transfusions within 4 previous weeks.
• History of clotting pathology.
• Advance renal failure with glomerular filtration rate < 30 ml/min (Cockcroft-Gault equation)
• Left main lesion.
• Target bifurcation located on a distal coronary segment.

Patients with stable or unstable coronary artery disease due to atherosclerosis involving a major bifurcation site, who undergo diagnostic or interventional invasive percutaneous coronary procedures with the use of optical coherence tomography (OCT) based on operator's choice.