Index of Microcirculatory Resistance After Immediate Versus Deferred Stenting in Patients With Acute Myocardial Infarction

Primary PCI with immediate stenting (IS) is the current standard of reperfusion strategy for STEMI. However, it is thought that IS may cause additional myocardial injury by increasing distal embolization of clot and atheromatous plaque debris. Only about 35% of patients without cardiogenic shock can achieve optimal myocardial tissue perfusion at the microvascular level, even after restoration of epicardial coronary artery patency. IS in highly pro-thrombotic and inflammatory milieu of IRA during primary PCI would increase distal embolization of clot and atheromatous plaque debris, and provoke the inflammation process, so deferred stenting after a cooling down period of IRA for several days, have a potential to mitigate or prevent microvascular obstruction (MVO). Among several methods to evaluate MVO after STEMI, IMR has been well known as an good indicator of MVO and strong predictor for short and long term clinical outcomes.