ABC | Volume 111, Nº4, Octuber 2018

Original Article Fractional Flow Reserve-Guided Strategy in Acute Coronary Syndrome. A Systematic Review and Meta-Analysis José Luís Martins, 1 Vera Afreixo, 2 José Santos, 1 Lino Gonçalves 3 Department of Cardiology, Baixo Vouga Hospital Center, 1 Aveiro - Portugal CIDMA/IBIMED/Department of Mathematics, University of Aveiro, 2 Aveiro - Portugal Department of Cardiology, Coimbra Universitary Hospital Center, 3 Coimbra - Portugal Mailing Address: José Luis Martins • Av. Artur Ravara. Aveiro E-mail: zeluismartins@gmail.com Manuscript received March 27, 2018, revised manuscript May 09, 2018, accepted May 09, 2018 DOI: 10.5935/abc.20180170 Abstract Background: There are limited data on the prognosis of deferral of lesion treatment in patients with acute coronary syndrome (ACS) based on fractional flow reserve (FFR). Objectives: To provide a systematic review of the current evidence on the prognosis of deferred lesions in ACS patients compared with deferred lesions in non-ACS patients, on the basis of FFR. Methods: We searched Medline, EMBASE, and the Cochrane Library for studies published between January 2000 and September 2017 that compared prognosis of deferred revascularization of lesions on the basis of FFR in ACS patients compared with non-ACS patients. We conducted a pooled relative risk meta-analysis of four primary outcomes: mortality, cardiovascular (CV) mortality, myocardial infarction (MI) and target-vessel revascularization (TVR). Results: We identified 7 studies that included a total of 5,107 patients. A pooled meta-analysis showed no significant difference in mortality (relative risk [RR] = 1.44; 95% CI, 0.9–2.4), CV mortality (RR = 1.29; 95% CI = 0.4–4.3) and TVR (RR = 1.46; 95% CI = 0.9–2.3) after deferral of revascularization based on FFR between ACS and non-ACS patients. Such deferral was associated with significant additional risk of MI (RR = 1.83; 95% CI = 1.4–2.4) in ACS patients. Conclusion: The prognostic value of FFR in ACS setting is not as good as in stable patients. The results demonstrate an increased risk of MI but not of mortality, CV mortality, and TVR in ACS patients. (Arq Bras Cardiol. 2018; 111(4):542-550) Keywords: AcuteCoronary Syndrome/physiopathology; PercutaneousCoronary Intervention/methods; CoronaryAngiography/ methods; Fractional Flow Reserve Myocardial/physiology; Microvessels; Vascular Resistance; Reproducibility of Results. Introduction Fractional flow reserve is a well-validated, effective technique to determine the functional significance of intermediate coronary lesions; FFR-guided percutaneous coronary intervention (PCI) improves clinical outcomes in patients with stable coronary disease. 1-3 Although robust data supports FFR use in stable coronary disease, its use in acute coronary syndrome (ACS) is less well investigated because maximal hyperemia is required to accurately measure FFR. In patients with ACS, microvascular changes may prevent vasodilatation thus affecting the validity of FFR. 1,4-6 These changes appear to be vessel-dependent (culprit vs. non-culprit) and related to the type of infarction – ST-elevation myocardial infarction (STEMI) vs. non-ST-elevation myocardial infarction (NSTEMI). 7 FFR values in the culprit vessel are recognized to be higher when measured during acute episodes than when measured after the microcirculation has had some time to recover. Higher FFR values are assumed to be caused by reduced levels of hyperemia in the culprit vessel due to embolization of thrombus and plaque, ischemic microvascular dysfunction andmyocardial stunning. Hence, efficacy of the use of FFR in culprit artery disease remains uncertain. 8,9 Multivessel coronary disease (MVD), observed in approximately 30-50% of patients presenting with STEMI and in 30-59% with NSTEMI, is associated with a poor prognosis. 10-12 Complete revascularization of hemodynamically significant vessels identified in the hemodynamic laboratory early after acute event appears attractive: this approach provides the patient with a well-defined, definitive therapeutic plan. However, several studies suggest that a FFR-guided revascularization strategy in ACS reduces the rate of coronary revascularization without compromising short-term safety. 13-15 However, the results of this approach are inconsistent in several studies involving patients with non-ACS. 13,14 Therefore, the aims of this study are to provide a systematic review of the current evidence of the deferral of PCI based on FFR in ACS patients and compare it with that supporting this decision in non-ACS patients. Methods Data sources and searches We systematically searched MEDLINE, EMBASE, and the Cochrane Library for relevant articles published between 542