No-reflow phenomenon in acute myocardial infarction: Relieve pressure from the procedure and focus attention to the patient

摘要

Re-opening of the culprit epicardial coronary artery in the early phase of an acute myocardial infarction does not mandatorily translate into an effective myocardial reperfusion. This is the case of the so- called “no-reflow phenomenon”, which refers to the failure to restore perfusion to the microvasculature supplying the myocardium, generally due to thrombotic occlusion of the pre-capillary and capillary bed. In ST- elevation myocardial infarction (STEMI), the incidence of no-reflow has been reported to be comprised between 11 and 41%, with a variability depending on patient, vessel, and lesion factors [1] Its appearance is as- sociated with a worse prognosis, especially in term of short and long mortality [2,3]. Angiographic diagnosis requires documentation of an impaired (<2) Myocardial Blush Grade (MGB), whereas a preserved TIMI flow (grade 3) alone, although associated with a lower risk of no- reflow, is not sufficient. Since there is no definitive treatment of no- reflow once it has occurred, prevention plays a pivotal role to avoiding this harmful complication. Although the mechanisms determining no- reflow are not still completely understood, it is now clear that its path- ogenesis is multifactorial. In fact, injury related to ischemia, reperfusion, endothelial dysfunction, distal thromboembolism and microvascular spasm are considered the principal underlying determinants [4]. A number of clinical, serologic, angiographic and procedural parameters have been identified in several studies as predictors of no-reflow. Due to heterogeneity of the populations studied, there is a disagreement on the relative importance of some of these parameters. Not surpris- ingly, a high thrombus burden increases the risk of no-reflow [5,6], due to dislodgement of atherothrombotic debris causing distal emboli- zation [7]. However, thrombus burden is only one predictor of no re- flow with other mechanisms that have to be searched in the concomi- tant presence of multiple, especially clinical, pro-thrombotic and/or pro-inflammatory patient characteristics. In fact, Mazhar et al. [6] showed in a cohort of 781 patients underwent primary percutaneous coronary intervention (pPCI) that no-reflow occurred more frequently in the older (>60 years), in the presence of high thrombus burden and in case of delayed presentation from symptom onset (>4 h). Interest- ingly, no lesion and pharmacological associations were documented.