Use of intracoronary imaging to guide optimal percutaneous coronary intervention procedures and outcomes

### Learning objectives Although it is the tool used by most interventional cardiologists to assess the severity of coronary artery disease and guide treatment, coronary angiography has many limitations because it is a lumenogram depicting shadowgraph, planar projections of the contrast-filled lumen that are often foreshortened rather than imaging the diseased vessel itself. Intravascular imaging (IVI)—first intravascular ultrasound (IVUS) and recently optical coherence tomography (OCT) and near infrared spectroscopy (NIRS) and even combined modalities that are now available—provides tomographic or cross-sectional images of the coronary arteries. These techniques aid in physician decision-making, selection of treatment strategies, stent optimisation and answering questions that arise during percutaneous coronary interventions (PCI). Randomised controlled trials, registries and meta-analyses consistently support procedural and long-term benefits of IVI-guided PCI especially drug-eluting stent (DES) implantation. ### IVUS versus OCT An IVUS image is formed when ultrasound bounces off the layers of the artery and returns to the transducer that both emits and receives the ultrasound. There are two types of IVUS: (1) mechanical and (2) synthetic aperture array. The mechanical catheter has a single transducer mounted at the tip of a flexible drive shaft that is rotated and advanced or withdrawn within a stationary, short-monorail imaging sheath to scan the artery; current mechanical transducer frequencies range from 40 MHz to 60 MHz. The 20 mHz synthetic aperture array catheter has multiple, tiny transducer elements permanently affixed around the circumference of the catheter tip; they are fired sequentially to produce cross-sectional images, and the entire catheter must be withdrawn or advanced to scan the vessel. The synthetic aperture array has the lowest transducer frequency and temporal and …