Slow flow and no reflow after percutaneous coronary intervention

Primary percutaneous coronary intervention is currently the standard of care for the treatment of acute ST-segment elevation myocardial infarction (STEMI). While it can restore flow in the infarcted artery in the majority of cases, some patients experience the so-called "no-reflow" phenomenon, which consists of abnormal myocardial reperfusion occurring after the occluded coronary artery has been opened. It is caused by microvascular obstruction (MVO), and its pathogenesis is multifactorial, including myocardial ischaemia, distal embolisation, and ischaemia-reperfusion injury, combined with individual susceptibility. Currently, there is no consensus on pharmacological or interventional strategies which can prevent or treat it. We herein discuss in detail the pathophysiology of the "no-reflow" phenomenon in STEMI patients, which is closely related to MVO, as well as potential pharmacological and interventional treatments tested in clinical studies.