The slowly accruing evidence on the treatment of patients with left main coronary artery (LMCA) disease drove evolution in guidelines, that currently establish equivalent safety and efficacy for percutaneous coronary intervention (PCI) as compared to surgery, with a class of recommendation that is subjected to the extension and complexity of concomitant coronary artery disease, as assessed by the SYNTAX score.

The severity of LMCA disease, although extremely relevant due to the extent of the supplied myocardium, is often difficult to assess with traditional angiography, due to lack of appropriate angiographic views, absence of a true "reference" segment, interaction with the intubating catheter. Intravascular techniques with either imaging or functional assessment have been variously tested, although with a disturbing rate of discordant results; moreover, they are frequently underused for a number of reasons, including the additional time needed to assess both left anterior descending (LAD) and left circumflex (LCx) arteries, technical challenges, costs and the small risk associated with maneuvering such devices. Fractional flow reserve (FFR) measured from the coronary angiogram (FFRangio) alone recently documented a high diagnostic accuracy compared with pressure-wire derived FFR.

As for the anatomical localization, the majority of LMCA lesions occur at the bifurcation, where PCI results are less favourable. The distal LMCA differs from the other bifurcations in several characteristics: a) a notable mismatch between the LMCA and the left anterior descending (LAD) artery, hampering the selection of an adequately sized stent, b) the presence of a trifurcation, with a large ramus arising from LMCA in about 10% of cases, c) the presence of left or co-dominant circulation, with the LMCA supplying all or nearly all left ventricular myocardium in about 15% of cases.

Therefore, although the European Bifurcation Club (EBC) recommends a provisional side branch approach in most cases of distal LMCA disease, the threshold for placing a second stent in the side branch may be lower in lesions located on LM bifurcation compared with non-LMCA bifurcations. As for double stenting, the evidence is controversial and a consensus is lacking. Moreover, the optimal treatment of patients with LM trifurcations is still undefined.

The aim of this study is therefore to determine the optimal strategy for the treatment of LM bifurcated lesions.

PCI access site and technique will be left at the operator's discretion, as well as antithrombotic management.

No limitation will be applied for the technique of PCI. As regards data collection and endpoints, Case Report Form (CRF) will be entered on a web-based platform, where study participants will be able to access and retrieve data at any time during study progress.

In-hospital outcomes will be recorded; all patients discharged alive will be followed up with a 30-day, 6-month, and 1-year telephone interview.

On a center-to-center voluntary basis, pre-PCI and post-PCI angiographic images (made blind regarding patients' identity) will be sent to a study angiographic core-lab for Quantitative Angiography Substudy. The images will be processed using a validated quantitative coronary angiography (QCA) Bifurcation software to assess quantitative data describing bifurcation geometry before and after LMCA PCI. In the Quantitative Angiography Substudy, on exploratory bases, FFRangio data reconstructed by angiographic software will be tested against stenosis LMCA lesion severity and LMCA PCI result.

Inclusion Criteria:

• Patients ≥18 years of age with a diagnosis of documented silent ischemia, stable angina, or acute coronary syndrome (ACS).
• PCI with single or multiple drug-eluting stent (DES) for the treatment of lesion located at LMCA bifurcation and defined as a diameter stenosis of ≥50% by visual estimation.

Exclusion Criteria:

• Patients who cannot give informed consent or have a life expectancy of ≤12 months;
• Pregnant or nursing mothers. Women of child-bearing age will be asked if they are pregnant or think that they may be pregnant.
• Contraindication or suspected intolerance to anticoagulant (heparin, bivalirudin) or oral antiplatelet therapy (aspirin, clopidogrel, prasugrel, ticagrelor).

Patients with a diagnosis of documented silent ischemia, stable angina, or ACS, undergoing PCI with single or multiple DES for the treatment of lesion located at LM coronary bifurcation and defined as a diameter stenosis of ≥50% by visual estimation.

Case Report Forms (CRF) will be shared among partecipating centers

12 Months