Intracoronary imaging in percutaneous coronary intervention: why, when, how and which from large, randomized trials

The introduction of intracoronary imaging (ICI) into clinical practice has been one of the major advances in percutaneous coronary intervention (PCI) for patients with atherosclerotic coronary artery disease. However, because the procedural advantages of ICI in routine clinical practice can be offset by higher costs and longer procedural times, high-quality evidence demonstrating the net clinical benefits of ICI guidance has long been awaited. The publication of eight large (n > 1,000 patients), international, randomized studies (the ILUMIEN IV, IVUS-ACS, IVUS-CHIP, IVUS-XPL, OCCUPI, OCTOBER, RENOVATE-COMPLEX-PCI and ULTIMATE trials) has provided substantial data on the clinical use of ICI guidance to improve the safety and outcomes of patients undergoing PCI. However, the heterogeneity of the study populations, lack of standardized criteria across ICI protocols and the mixed results of randomized trials have left uncertainty about why and when the use of ICI confers a benefit in real-world settings. In this Review, by discussing the study characteristics and procedural aspects that contributed to the consistency and heterogeneity across trials, we provide a practical and comprehensive appraisal of the appropriateness - why, when, how and which - of ICI guidance in the clinical decision-making process for contemporary PCI, with the overall aim of improving clinical outcomes.