The updated guidelines from the European Society of Cardiology (ESC) for chronic coronary syndrome (CCS) have upgraded the use of IVUS and OCT to a class IA recommendation for complex PCI, based on evidence showing a reduction in serious clinical events, including mortality, compared to conventional angiography alone. Despite this, IVUS and OCT are underutilized in daily practice due to factors such as time, cost, and limited technology availability. Investigating the reasons behind this underuse is necessary, especially now that these technologies are more accessible and cost-effective. Additionally, OCT could be particularly helpful in specific cases such as coronary bifurcations and severe calcifications, warranting further evaluation of its use in these settings.

The objective of the study OCT2ACT is to investigate:

• The main reasons/barriers limiting the use of intracoronary imaging in complex PCI cases where it is indicated as suggested by guidelines;
• The main reasons behind the selection of IVUS or OCT in such patients;
• In cases where OCT is used, how this technology can influence the procedural planning and optimization in complex clinical settings.

The participating centers will include three cohorts of patients:

1. Cohort intracoronary imaging NO: patients who meet the inclusion/exclusion criteria, but did not undergo intracoronary imaging (IVUS or OCT) due to operator's decision.

   The aim is to describe the main reasons/barriers for not using imaging.

2. Cohort intracoronary imaging YES according to guidelines recommendation: patients who meet the inclusion/exclusion criteria and underwent intracoronary imaging as recommended by guidelines.

   The aim is to understand the main reasons for the decision to use IVUS or OCT and the clinical benefits perceived by the operator.

3. Cohort intracoronary imaging YES outside guidelines recommendation: patients who meet the inclusion/exclusion criteria and underwent intracoronary imaging (IVUS or OCT) outside.

The last update of European Society of Cardiology (ESC) chronic coronary syndrome (CCS) guidelines upgraded the use of intravascular ultrasound (IVUS) imaging and optical coherence tomography (OCT) to class IA in the setting of complex percutaneous coronary intervention (PCI) (in particular left main, true bifurcations, and long lesions).

This strong level of recommendation is based on the recent evidence that intracoronary imaging reduces the incidence of hard clinical endpoints, including mortality, as compared to conventional angiography alone.

Yet, there is compelling evidence documenting the under-utilization of IVUS and OCT in daily practice. Many potential reasons, including time, costs, limited availability of technology, expertise of the operators have been suggested. However, no specific study investigated the reasons behind this malpractice. In particular, these reasons should be investigated now that intracoronary imaging has been upgraded to class I recommendation and that many technologies are available significantly reducing the economic burden. In addition, there are some particular anatomic subsets where OCT could be particularly helpful (bifurcations, severe calcification, acute coronary syndrome patients) and it could be interesting to assess the penetration of this technology in this subset of patients. Finally, these devices can be used also in anatomical subsets (diagnosis and procedural guidance) outside from Guidelines recommendations and it is important to assess their safety and clinical advantage in this setting.

Objective

The OCT2ACT study aims to investigate:

• The main reasons/barriers limiting the use of intracoronary imaging in complex PCI where it is indicated as suggested by guidelines
• The main reasons behind the selection of IVUS or OCT in complex PCI
• In complex PCI guided by OCT, How OCT can influence the procedural planning and optimization in complex clinical settings.

The OCT2ACT is an observational, prospective, multicenter, investigator-driven study.

Participating centers will include three different cohorts of patients:

1. Cohort intracoronary imaging NO In this cohort, the investigators will include all the patients matching inclusion/exclusion criteria, but in whom intracoronary imaging (IVUS or OCT) was not used (operator's decision). The aim is to have a description of the main reasons/barriers that led to the avoidance of imaging utilization.
2. Cohort intracoronary imaging YES according to guidelines recommendation In this cohort, the investigators will include all the patients matching inclusion/exclusion criteria in whom intracoronary imaging (IVUS or OCT) was used (operator's decision) according to guidelines recommendation. The aim is to understand the main reasons behind the decision to use IVUS or OCT and the clinical advantages perceived by the operators.
3. Cohort intracoronary imaging YES outside guidelines recommendation In this cohort, the investigators will include all the patients matching inclusion/exclusion criteria in whom OCT was used (operator's decision) outside Guidelines recommendations. The aim is to understand the main reasons behind the decision to use OCT outside guidelines recommendation, its safety and the clinical advantages perceived by the operators.

After Ethic Committee approval and site initiation visit, each participating center will recruit consecutive patients for a time window of 3 months.

1. Cohort intracoronary imaging NO

   • Inclusion criteria

   Patients undergoing clinically indicated PCI and having at least one of the following criteria (suggestive for complex PCI) without receiving intracoronary imaging:

   • Long lesion (>38 mm)

   • True bifurcation involving side-branch with a reference diameter of >2.5 mm and Medina 1.1.1

   • Left main bifurcation

     • Exclusion criteria

   • Refusal of informed consent

2. Cohort intracoronary imaging YES according to guidelines recommendation

   • Inclusion criteria

   Patients undergoing clinically indicated PCI with the guidance of intracoronary imaging (OCT or IVUS) and having at least one of the following criteria (suggestive for complex PCI) receiving imaging:

   • Long lesion (>38 mm)

   • True bifurcation involving side-branch with a reference diameter of >2.5 mm and Medina 1.1.1

   • Left main bifurcation

     • Exclusion criteria

   • Refusal of informed consent

3. Cohort intracoronary imaging YES outside guidelines recommendation

   • Inclusion criteria Patients undergoing IVUS or OCT use.

   • Exclusion criteria

     • Long lesion (>38 mm)
     • True bifurcation involving side-branch with a reference diameter of >2.5 mm and Medina 1.1.1
     • Left main bifurcation
     • Refusal of informed consent

Patients undergoing PCI and receiving or not receiving imaging according to ESC indication guidelines. Patients undergoing coronary artery angiography and/or PCI and receiving imaging in a setting outside from ESC indication guidelines.