ABC | Volume 114, Nº2, February 2020

Original Article Evaluation of Myocardial Ischemia with iFR (Instantaneous Wave- Free Ratio in the Catheterization Laboratory: A Pilot Study Heitor Cruz Alves Vieira, 1 M aria Cristina Meira Ferreira, 3 L eonardo Cruz Nunes, 1 Carlos José Francisco Cardoso, 1 Emilia Matos do Nascimento, 2,4 Gláucia Maria Moraes de Oliveira 2 Hospital Naval Marcilio Dias, 1 Rio de janeiro, RJ – Brazil Universidade Federal do Rio de Janeiro, 2 Rio de Janeiro, RJ – Brazil Hospital Federal dos Servidores do Estado, 3 Rio de Janeiro, RJ – Brazil Fundação Centro Universitário Estadual da Zona Oeste - UEZO, 4 Rio de Janeiro, RJ – Brazil Mailing Address: Maria Cristina Meira Ferreira • Hospital Federal dos Servidores do Estado - Serviço de Hemodinâmica - Rua Sacadura Cabral 178 - Saúde - Rio de Janeiro, RJ – Brazil E-mail: mc.meira.ferreira@gmail.com Manuscript received October 20, 2018, revised manuscript February 15, 2019, accepted March 10, 2019 DOI: https://doi.org/10.36660/abc.20180298 Abstract Background: The Instantaneous Wave-Free Ratio (iFR) is an invasive functional evaluation method that does not require vasoactive drugs to induce maximum hyperemia Objective: To evaluate the contribution of the iFR to the therapeutic decision-making of coronary lesions in the absence of non-invasive diagnostic methods for ischemia, or in case of discordance between these methods and coronary angiography. Method: We studied patients older than 18 years, of both sexes, consecutively referred for percutaneous treatment betweenMay 2014 and March 2018. Coronary stenotic lesions were classified by visual estimation of the stenosis diameter into moderate (41-70% stenosis) or severe (71%-90%). An iFR ≤ 0.89 was considered positive for ischemia. Logistic regression was performed using the elastic net, with placement of stents as outcome variable, and age, sex, arterial hypertension, diabetes, dyslipidemia, smoking, family history, obesity and acute myocardial infarction (AMI) as independent variables. Classification trees, ROC curves, and Box Plot graphs were constructed using the R software. A p-value < 0.05 was considered statistically significant. Results: Fifty-two patients with 96 stenotic lesions (56 moderate, 40 severe) were evaluated. The iFR cut-off point of 0.87 showed a sensitivity of 0.57 and 1-specificity of 0.88, demonstrating high accuracy in reclassifying the lesions. Diabetes mellitus, dyslipidemia, and presence of moderate lesions with an iFR < 0.87 were predictors of stent implantation. Stents were used in 32% of lesions in patients with stable coronary artery disease and AMI with or without ST elevation (non-culprit lesions). Conclusion: The iFR has an additional value to the therapeutic decision making in moderate and severe coronary stenotic lesions, by contributing to the reclassification of lesions and decreasing the need for stenting. (Arq Bras Cardiol. 2020; 114(2):256-264) Keywords: Myocardial Ischemia, Fractional Flow Reserve Myocardial; Stents; Coronary Artery Disease; Risk factors; Percutaneous Coronary Intervention. Introduction In functional evaluation of coronary stenosis, the use of fractional flow reserve (FFR) to measure pressure instead of flow has been recommended by the American College of Cardiology-American Heart Association, the European Society of Cardiology, and the Brazilian Society of Hemodynamics and Interventional Cardiology guidelines 1-6 in case of absence or inconclusive results from non-invasive methods to assess ischemia. FFR is an easy-to-perform technique and its efficacy has been demonstrated by several clinical trials, especially those on stable coronary artery disease patients. However, the FFR method is not widely used in clinical practice. One reason for that is that FFR is measured during maximal hyperemia, which is achieved by administration of vasodilator drugs (e.g. adenosine). 7 The instantaneous wave-free ratio (iFR) is a recent, invasive method for functional diagnosis of coronary stenosis, introduced to solve some FFR-related issues, such as the need for intravenous drugs and new vascular access, with higher risk of complications. 8-10 The comparison between these methods showed a strong correlation of iFR < 086 with positive FFR (≤ 0.80) for ischemia, and of iFR > 0.93 with negative FFR (FFR > 0.80) for ischemia, indicating the high accuracy of the method. Values of iFR located in the range of 0.86–0.93 (called the “grey-zone”) showed a weak correlation, and results were confirmed by FFR. This analysis using both iFR and FFR is known as a hybrid approach. 11,12 The iFR was subsequently validated in randomized, controlled clinical trials which showed that the method was non-inferior to FFR, with cut-off points of 0.89 and 0.80 for iFR and FFR, respectively. 6 The iFR was also shown to be faster to perform and have less adverse events compared with FFR. 10-12 256