ABC | Volume 114, Nº2, February 2020

Short Editorial Chamié & Abizaid Invasive physiological assessment: from binary to continuous Arq Bras Cardiol. 2020; 114(2):265-267 1. Fihn SD, Gardin JM, Abrams J, Berra K, Blankenship JC, Dallas AP, et al 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and managementofpatientswithstable ischemicheartdisease. JAmCollCardiol . 2012;60(24):e44–e164. 2. Neumann FJ, Sousa-Uva M, Ahlsson A, Alfonso F, Banning AP, Benedetto U, et al. 2018 ESC/EACTS Guidelines on myocardial revascularization. Eur Heart J . 2019;40:87–165. 3. Knuuti J, Wijns W, Saraste A, Capodanno D, Barbato E, Funck-Brentano C, et al. 2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes. Eur Heart J . 2020;41(3):407-77. 4. Topol EJ, Nissen SE. Our preoccupation with coronary luminology: The dissociation between clinical and angiographic findings in ischemic heart disease. Circulation . 1995;92(8):2333–42. 5. Grondin CM, Dyrda I, Pasternac A, Campeau L, Bourassa MG, Lespérance J. Discrepancies between cineangiographic and postmortem findings in patients with coronary artery disease and recent myocardial revascularization. Circulation . 1974;49(4):703–8. 6. Brueren BRG, Ten Berg JM, Suttorp MJ, Bal ET, Ernst JMPG, Mast EG, et al. How good are experienced cardiologists at predicting the hemodynamic severity of coronary stenoses when taking fractional flow reserve as the gold standard. Int J Cardiovasc Imaging . 2002;18(2):73–6. 7. Tonino PAL, Fearon WF, De Bruyne B, Oldroyd KG, Leesar MA, Ver Lee PN, et al. Angiographic Versus Functional Severity of Coronary Artery Stenoses in the FAME Study. Fractional Flow Reserve Versus Angiography in Multivessel Evaluation. J Am Coll Cardiol . 2010;55(25):2816–21. 8. BodenWE, O’Rourke RA, Teo KK, Hartigan PM, MaronDJ, KostukWJ, et al. Optimal medical therapy with or without PCI for stable coronary disease. N Engl J Med . 2007;356(15):1503–16. 9. HachamovitchR,BermanDS,ShawLJ,KiatH,Cohen I,ArthurCabico J,etal. Incrementalprognosticvalueofmyocardialperfusionsinglephotonemission computed tomography for the prediction of cardiac death: Differential stratification for risk of cardiac death and myocardial infarction. Circulation . 1998;97(6):535–43. 10. Zimmermann FM, Ferrara A, Johnson NP, Van Nunen LX, Escaned J, Albertsson P, et al. Deferral vs. performance of percutaneous coronary intervention of functionally non-significant coronary stenosis: 15-year follow-up of the DEFER trial. Eur Heart J . 2015;36(45):3182–8. References Although the clinical decision for revascularizing coronary stenoses is binary, which ends up justifying the search for cut-off points that determine the choice of one strategy over another, we advocate that invasive coronary physiology should be assessed in a more comprehensive, continuous and interpretative manner. In this sense, similarly to what was demonstrated in the classical study by Hachamovitch et al., 21 robust evidence indicates a linear association between FFR and the risk of adverse cardiac outcomes. Adverse outcome rates increased proportionally with reduced FFR values, revealing a risk continuum, far beyond a fixed cut-off point. 22,23 In addition, lesions with lower FFR values are the ones which receive the greatest absolute benefits from PCI. 23 On the other hand, for lesions with FFR values around the cut-off point, the benefits of revascularization are lower and at times uncertain. Although ischemia determined at the vessel level – in other words, “positive” or “negative”, as the sum of all lesions throughout the artery length – has been the traditional basis for FFR utilization, a series of technological advances have allowed for a more global and systematic approach to assessing the presence of myocardial ischemia. Through manual pullback of the pressure sensor, the non-hyperemic iFR index allows for the assessment of the functional impact of each lesion along the target vessel segment. Moreover, overlaying these results onto the angiographic images provides a valuable functional- anatomical co-registration. This technique yields a more accurate characterization on the distribution of the physiological effects of coronary heart disease, enabling the diagnosis of focal and diffuse disease (which frequently coexist in the same vessel), in addition to quantifying the contribution of each for the iFR value at the artery level. Furthermore, it is possible to simulate several PCI strategies and estimate the physiological results of the possible intervention. Hence, the result is an evolution from the binary negative/positive to a more comprehensive assessment of the physiological impact of CAD, and the potential benefits of PCI, in case this is the chosen therapeutic strategy. This concept proved to be particularly important in the recent DEFINE-PCI 24 pilot study. In a population of 500 patients undergoing PCI with stent implantation, whose procedures were considered successful by angiographic criteria, iFR pullback showed that 24% of the patients treated remained with physiologically significant stenoses. It is worth mentioning the finding that in more than 80% of the cases, the abnormal iFR matched focal stenoses, which are easily treatable, reaffirming the limitations of angiography in identifying coronary flow-limiting lesions. In cases with serial lesions or diffuse disease, the hyperemic flow through one stenosis is affected by the presence of another stenosis in the same artery, making interpretation of FFR values challenging in this frequent anatomic subset. On the other hand, resting flow is stable across almost the entire range of epicardial coronary stenosis severity. Thus, changes in resting pressure are more predictable, and the contribution of each stenosis along the vessel can be more easily estimated, representing a practical advantage of iFR over FFR. 25,26 Therefore, we believe that the introduction of new indexes (e.g. angiography-derived FFR, coronary computed tomography-derived FFR, resting indexes, among others) and new possibilities of understanding the functional effects of coronary stenosis have promoted growing interest in invasive and non-invasive assessment of cardiac physiology in the “post-FFR era”. We keep waiting the development of new physiological tools that enable the measurement of myocardial ischemia in an easier and more accurate way (instead of using surrogate outcomes), as well as tools to simplify the study of the coronary microcirculation status. These advances will contribute to a more individualized approach to coronary revascularization decision-making, better understanding of focal and diffuse disease, and treatment of post-MI patients whose microcirculation has been impaired. Until then, we advance our application of physiological assessment, from binary to continuous. 266