ABC | Volume 114, Nº2, February 2020

Original Article Vieira et al. Evaluation myocardial ischemia with iFR Arq Bras Cardiol. 2020; 114(2):256-264 Table 1 – Characteristics of the patients Variables n (%) Number of patients 52 (100%) Age Mean ± SD 66.85 ± 11.27 Median (minimum, maximum) 66.5 (41, 86) Sex Female 14 (26.9%) Male 38 (73.1%) Arterial hypertension 45 (86.5%) Diabetes mellitus 22 (42.3%) Dyslipidemia 36 (69.2%) Smoking 17 (32.7%) Family history of coronary artery disease 11 (21.2%) Obesity 3 (5.8%) Previous infarction 7 (13.5%) Clinical manifestation Stable angina 19 (36.5%) Myocardial acute infarction 21 (40.4%) Others 12 (23.1%) Moderate stenoses Without stenosis 16 (30.8%) With stenosis 1 lesion 18 (34.6%) 2 lesions 16 (30.8%) 3 lesions 2 (3.8%) Severe stenoses Without stenosi 25 (48.1%) With stenosis 1 lesion 16 (30.8%) 2 lesions 9 (17.3%) 3 lesions 2 (3.8%) Stents Without stent 30 (57.7%) With stent 1 stent 15 (28.8%) 2 stents 6 (11.5%) 3 stents 1 (1.9%) SD: standard deviation. composite outcomes in theDEFINE FLAIR study and for all‑cause mortality, non-fatal AMI, and unplanned revascularization in the iFR-SWEDEHEART study after one-year follow-up. It is worth pointing out that in the iFR‑SWEDEHEART trial, 17.5% of the patients treated had acute coronary syndrome. 7,23 There are no randomized studies comparing iFR-guided revascularization versus medical therapy. Also, there is no strong evidence for the use of this new technique in AMI‑related lesions or extrapolation of the outcomes to follow-up periods longer than one year. However, in a recent European guideline, a Class I recommendation with a level of evidence A has been issued to the iFR for intermediate lesions with no documentation of previous ischemia. 3 The analysis of coronary physiology as a prerequisite for the prognostic assessment of moderate stenosis will be probably be incorporated to clinical practice, especially considering the iFR as an alternative to the FFR. As compared with the FFR, iFR is easier and faster to be performed, and prevent the side effects caused by intravenous infusion of vasodilators, especially CAD with acute clinical manifestations. 13 In this context, this study corroborates previous findings of the literature, 9,24 showing that, in situations where there were disagreements between anatomic and functional methods, moderate stenotic lesions in coronary angiography were reclassified, preventing stent implantation in 58% of the cases. It is of note that the use of iFR helped in the therapeutic decision-making process, for stent placement, in moderate stenotic lesions in patients with stable CAD, and in non-culprit lesions of STEMI and non-STEMI patients. The combined analysis of the DEFINE-FLAIR and the iFR- SWEDEHEART studies, 13 involving 440 patients with acute coronary syndrome, demonstrated a relative advantage of the iFR over FFR in these patients, but more robust studies are needed to confirm this. In the iFR-SWEEDHEART study, 38% of the patients had acute coronary syndrome, 17% of them with AMI without ST elevation, and 21% with unstable angina. The DEFINE‑FLAIR trial, however, also included patients with AMI with ST elevation, 3.9% in the iFR group and 3.4% in the FFR group, in which the non-culprit vessel was analyzed at least 48 hours after the acute event. Quantification of myocardial ischemia in the presence of serial lesions is challenging, 25 as it is frequently seen in the descending coronary artery (DA), where the FFR has not been validated. In our study, 8 patients (15%) showed two or three serial lesions in the DA, with a total of 17 lesions analyzed by iFR. The ischemic component of the lesions was assessed, which was successfully treated with the placement of 5 stents, with no need to approach all the lesions. These data are corroborated by the iFR-GRADIENT Registry with 128 patients, in which the use of the iFR showed high accuracy in reclassifying the lesions in 31% of the cases. 26 In the present study, the iFR cut-off of 0.87 showed high accuracy, with 0.57 sensitivity and 1-specificity of 0.88. The inclusion of severe lesions in our analysis may explain the lower sensitivity, as compared with literature data. Discordance between FFR and iFR has been reported to occur in 20% of the cases and may be explained by differences in the hyperemic coronary flow velocity, 27 which, in the presence of FFR (+) and iFR (-), is similar to that reported in non-stenotic vessels (by angiography). It is possible that such divergence is associated with pathophysiological mechanisms of the measures. Significant pressure differences caused by stenosis between resting and hyperemia indicate 259