摘要： Coronary angiography represents both the gold standard for diagnosis of coronary artery disease and the main guidance for percutaneous coronary intervention (PCI). Yet, coronary angiography is well known to not be optimal in appreciating the whole spectrum of lesions that may cause clinical problems in patients with coronary artery disease. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) represent the 2 contemporary invasive intracoronary imaging modalities aimed at improving the detection of coronary details. Their potential is extraordinary but their use for improving coronary disease diagnosis is not standardized. Moving from diagnosis to treatment, PCI based on drug-eluting stent (DES) implantation often requires a series of manipulations with different techniques and devices. Last generation DES types have similar technical features and share a comparable ability to scaffold coronary lesions. Not surprisingly, lesion complexity is known to be associated with increased procedure challenges that may be tackled by different strategies. The selection of devices and the assessment of appropriate DES implantation may be based on either angiography or intracoronary imaging techniques like IVUS or OCT. Both techniques have evolved over time and offer the possibility to see details of coronary lesions and stent/vessel interactions that are impossible to be captured and measured by angiography. So far, thousands of studies with different designs have been performed, but they have not been able to make interventional cardiologists act in a homogeneous way. Consequently, intravascular imaging is selected on the basis of individual yield, with an impressive variability across different countries and operators. Reimbursement issues are part of the game but do not entirely explain the overall underutilization of intravascular imaging (especially in Western countries where a lot of expensive devices are routinely incorporated in interventional practice). In reality, the application of intracoronary imaging adds complexity to PCI, requires adequate technical skills, and by itself does not necessarily improve the clinical outcome. As compared with angiography guidance, IVUS and OCT are able to provide (in real time) many more coronary details. Such angiographically invisible details need to be recognized by the operator to properly react to improve the clinical outcome of treated patients. Because of the impressive amount of details and possible measures/cutoffs, the identification of both impactful features (deserving attention) and best reactions (additional technical steps with corrective efficacy) is pivotal. Yet, data collected by IVUS studies have not been concordant and this has resulted in overall limited clinical penetration: many catheterization laboratories are actually working without any access to intracoronary imaging. Furthermore, although rare, imaging catheter-related complications may occur so that a safety issue has to be considered any time the expected benefit is not well established in clinical practice. On the bases of these concepts, it is evident that the intracoronary imaging clinical impact may come from the correct identification and appropriate processing of those details that may help (1) to improve the PCI strategy (technique/device selection, that is, PCI planning) and (2) to facilitate the achievement of improved stenting result (ie, PCI optimization). As shown in the Figure, among all the information captured by intracoronary imaging, a limited series of imaging-based pre-PCI findings can be easily incorporated in the PCI planning (lesion preparation and stent selection). Similarly, some key intra-PCI findings (stent underexpansion, stent edge dissections, and strut malapposition) can be searched in order to optimize the stent implantation result. The feasibility of this approach is supported by the daily experience of many high volume centers. Yet, the overall clinical impact of image guidance in PCI is still unrecognized, and large studies in the field are needed. Recently-collected data started shedding new light on both IVUS and OCT. The large study by Maehara et al, although not randomized, allowed to run a propensity-matched comparison between thousands of IVUS-guided and angiography-guided procedures. IVUS use was associated with different procedure conduction and reduced major adverse events incidence at up to 2 years. Of note, the clinical benefit comprised significant improvements of hard end points, namely stent thrombosis, myocardial infarction, and cardiac mortality. Such results fit well with the recent ULTIMATE prospective randomized trial (Intravascular Ultrasound Guided Drug Eluting Stents Implantation in 'All-Comers' Coronary Lesions). The ULTIMATE investigators randomized 1448 all-comer patients who required DES implantation to either IVUS guidance or angiography guidance. As compared with angiography, randomization to IVUS guidance was associated with different procedure course (higher contrast administration, larger and longer stents, and higher inflation pressures) and warranted lower target vessel failures with IVUS at 12 months. OCT, as compared with IVUS, represents a younger technique, but data are growingly been collected because it has the appeal of offering higher resolution. The specific image generation process of OCT translates into the need of dedicated experience but has the potential for shorter learning curve. The possible clinical impact of OCT use in PCI guidance has been started to be highlighted by the results of the CLI-OPCI II study (Centro per la Lotta Contro l'Infarto-Optimisation of Percutaneous Coronary Intervention II). In this large registry, specific definitions for OCT features of suboptimal stent results were found to be independently associated with adverse clinical outcome after PCI. For sure, more complex PCIs (where the risk of stent thrombosis and restenosis is higher), are expected to benefit more from PCI refinements. Thus, two large prospectively randomized trials (OCTOBER, and ILUMIEN IV, and URL: https://www.clinicaltrials.gov. Unique identifier: NCT03507777) comparing OCT and angiographic guidance are actually ongoing and have been powered to explore the benefit of OCT guidance (using rigorous OCT-based PCI optimization algorithms) in, respectively, bifurcated lesions and complex patients. In conclusion, intravascular imaging modalities are entering a new era because the recently collected data seem to show new thresholds and targets for PCI planning and optimization. Thus, IVUS and OCT are going to become the ideal glasses that interventional cardiologists should wear anytime something looks unclear before, during or after PCI. Appropriate education, standardization of operative protocols and definitions of best clinical settings for application represent the future challenges for the intravascular imaging clinical implementation.