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Refining percutaneous coronary intervention: intracoronary imaging, haemodynamics, P2Y12 antagonists, and public outcomes reporting.

Percutaneous coronary intervention (PCI) is a remarkable success story and a lesson to sceptics as well. Although Andreas Grüntzig’s seminal first procedure went smoothly with an amazing and longstanding result after two balloon inflations, PCI remained a risky and complication-prone procedure initially. Had it not have been for its elegance and vision, PCI would have been abandoned due to the risk of acute occlusions and its high rate of restenosis. However, against all odds, step by step, the procedure was improved and refined, thanks to guidewires, stents, antithrombotic medication, secondary prevention, and the experience of operators and centres. Due to the limitation of angiography, which does not visualize the coronary vascular wall where the disease process occurs, intracoronary imaging was developed. This is reviewed in the Fast Track contribution ‘Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions’ by Thomas William Johnson and colleagues from the University Hospitals Bristol NHS Foundation Trust in the UK. The experts discuss the clinical use of intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near infrared spectroscopy (NIRS)–IVUS, as a continuation of their Part 1 document. They remind us that invasive imaging facilitates angiographic interpretation and guides treatment in acute coronary syndromes. It further provides diagnostic information in angiographically ambiguous lesions and allows assessment of plaque morphology. This second document focuses on features of culprit and vulnerable coronary plaques, offers guidance on when to adopt an intracoronary imaging-guided approach, and provides an appraisal of intravascular imaging-derived metrics to define the haemodynamic significance of coronary lesions. The benefit–risk ratio of PCI was further optimized with the introduction of haemodynamic assessment of lesion severity during hyperaemia using fractional flow reserve (FFR) with pressure wires and recently also with computed tomography. As FFR is time-consuming, non-hyperaemic tests such as the resting instantaneous wavefree ratio or iFR have been developed and validated against positron emission tomography. In their article entitled ‘Diastolic pressure ratio: new approach and validation vs. the instantaneous wave-free ratio’, Nils P. Johnson and colleagues from the University of Texas Medical School at Houston, USA investigated this further. To test for unique physiological properties of the wavefree period during resting coronary pressure measurements, they compared post-hoc a diastolic pressure ratio and Pd/Pa (referring to the ratio of the distal coronary pressure to proximal aortic pressure) against iFR in 893 lesions of 833 patients. The mean difference between the diastolic pressure ratio and iFR was minimal and mirrored the difference of two iFRs repeated immediately. Minor variations in the definition of diastolic pressure ratio changed its value by <1–2% over a broad range of the cardiac cycle. A linear transform of Pd/Pa showed very good diagnostic performance. Post-hoc iFR values were validated against real-time iFR values and matched almost exactly. Thus, the diastolic pressure ratio offers numerical equivalency to iFR. Despite different technical approaches for identifying the relevant period of diastole, the agreement between the diastolic pressure ratio and iFR and the insensitivity of the diastolic pressure ratio to minor variations in its definition further confirm numerical equivalency among resting metrics. A major breakthrough for the success of PCI was the introduction of dual antiplatelet therapy or DAPT, with one antagonizing the P2Y12 receptor plus aspirin. While ticlopidine was effective, but had