Novel insights into an “old” phenomenon: the no reflow

- No reflow (NR) represents the inability of a previously ischemic region to be reperfused. NR pathogenesis is complex and multifactorial. Single pathogenetic components have a different role in each single patient;
- There are conflicting results regarding risk factors for NR. Time to reperfusion and ischemic area are generally considered the most important risk factors;
- NR can be either reversible (due to functional changes in coronary microcirculation) or sustained (caused by structural damages);
- NR is not uncommon after primary PCI for STEMI occurring between 10% and 50% of cases, depending upon the assessing method; Cardiac magnetic resonance has gained increasing importance in the diagnosis and characterization of NR. It has a high sensitivity for NR assessment;
- There is no single effective drug for NR treatment, also due to the complex pathogenesis. A combination of NR prevention and treatment with different strategies should be used nowadays, awaiting for the development of new effective drugs.

Coronary artery diseases and particularly acute myocardial infarction are the leading causes of mortality and morbidity in western countries. Despite the achievements of the last decades with the advent of double antiplatelet therapy, new antithrombotics and reperfusion strategies (either pharmacological or mechanical), many patients still have adverse cardiovascular events after ST-segment elevation acute myocardial infarction; at least some of these adverse events are related to the no reflow phenomenon that occurs after primary percutaneous coronary intervention. In our review we will discuss the various aspects of this phenomenon.