  Citation: Pantea-Ros , an, L.R.; Bungau, S.G.; Radu, A.-F.; Pantea, V.A.; Moisi, M.I.; Vesa, C.M.; Behl, T.; Nechifor, A.C.; Babes, E.E.; Stoicescu, M.; et al. A Narrative Review of the Classical and Modern Diagnostic Methods of the No-Reflow Phenomenon. Diagnostics 2022, 12, 932. https:// doi.org/10.3390/diagnostics12040932 Academic Editor: Francesco Sessa Received: 9 March 2022 Accepted: 7 April 2022 Published: 8 April 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). diagnostics Review A Narrative Review of the Classical and Modern Diagnostic Methods of the No-Reflow Phenomenon Larisa Renata Pantea-Ros , an 1 , Simona Gabriela Bungau 2,3, * , Andrei-Flavius Radu 2,4, *, Vlad Alin Pantea 5 , Mădălina Ioana Moisi 4 , Cosmin Mihai Vesa 4 , Tapan Behl 6 , Aurelia Cristina Nechifor 7 , Elena Emilia Babes 1 , Manuela Stoicescu 1 , Daniela Gitea 3 , Diana Carina Iovanovici 2 and Cristiana Bustea 4 1 Department of Medical Disciplines, Faculty of Medicine and Pharmacy, University of Oradea, 410073 Oradea, Romania; larisa.rosan@yahoo.com (L.R.P.-R.); babes.emilia@gmail.com (E.E.B.); manuela_stoicescu@yahoo.com (M.S.) 2 Doctoral School of Biological and Biomedical Sciences, University of Oradea, 410087 Oradea, Romania; diana_iovanovici@yahoo.com 3 Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania; gitea_daniela@yahoo.co.uk 4 Department of Preclinical Disciplines, Faculty of Medicine and Pharmacy of Oradea, University of Oradea, 410073 Oradea, Romania; mada_vidican@yahoo.ro (M.I.M.); v_cosmin_15@yahoo.com (C.M.V.); cristianabustea@yahoo.com (C.B.) 5 Department of Dental Medicine, Faculty of Medicine and Pharmacy, University of Oradea, 410073 Oradea, Romania; panteavladalin@yahoo.ro 6 Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India; tapanbehl31@gmail.com 7 Analytical Chemistry and Environmental Engineering Department, Polytechnic University of Bucharest, 011061 Bucharest, Romania; aureliacristinanechifor@gmail.com * Correspondence: sbungau@uoradea.ro (S.G.B.); andreiflavius.radu@gmail.com (A.-F.R.) Abstract: The incidence of the no-reflow (NR) phenomenon varies depending on the diagnostic criteria used. If just the angiographic criteria are considered (i.e., a degree of thrombolysis in myocardial infarction ≤2), it will be found that the incidence of NR is quite low; on the other hand, when the myocardial NR is taken into account (i.e., a decrease in the quality of myocardial reperfusion expressed by the degree of myocardial blush), the real incidence is higher. Thus, the early establishment of a diagnosis of NR and the administration of specific treatment can lead to its reversibility. Otherwise, regardless of the follow-up period, patients with NR have a poor prognosis. In the present work, we offer a comprehensive perspective on diagnostic tools for NR detection, for improving the global management of patients with arterial microvasculature damage, which is a topic of major interest in the cardiology field, due to its complexity and its link with severe clinical outcomes. Keywords: diagnostic methods; no-reflow phenomenon; electrocardiogram; echocardiogram; throm- bolysis; acute myocardial infarction; myocardial blush grade 1. Introduction The no-reflow (NR) phenomenon is highlighted when, following a myocardial in- farction (MI), after the efficient unclogging of the epicardial coronary artery involved in the infarction, inadequate myocardial infusion is observed. Although effective methods of vascular permeabilization (such as coronary angiography) are currently available, the incidence of the phenomenon remains high, being found in 0.6 to 3.2% of patients who have had percutaneous coronary intervention (PCI) [1–3]. Coronary NR, detected angiographically, occurs when the degree of thrombolysis in myocardial infarction (TIMI) flow and the myocardial blush grade (MBG) is ≤2, and has been found in 2% of patients who underwent interventional myocardial revascularization. The two types of NR are as follows: Diagnostics 2022, 12, 932. https://doi.org/10.3390/diagnostics12040932 https://www.mdpi.com/journal/diagnostics