Deferred Stenting in Patients With Anterior Wall STEMI

Study background The main treatment for acute ST segment elevation myocardial infarction due to thrombogenesis and complete occlusion resulting from rupture or erosion of the atherosclerotic plaque in the coronary artery is to rapid open of the coronary artery through the coronary intervention. Infarction-associated epicardial coronary arteries reach Thrombolysis In Myocardial Infarction (TIMI) 3 blood flow in approximately 90% of patients after primary coronary intervention. However, many of these patients had microvascular dysfunction assessed by myocardial brush and ST segment complete response, and only about 35% of these patients achieved ideal reperfusion in which blood flow was smoothly delivered to the myocardium and tissue. A "no-reflow" phenomenon or microvascular obstruction, a serious form of microvascular dysfunction, raises the late mortality rate of patients who underwent reperfusion from 1.9 to 7.1 times. It is also well known that the phenomenon increases the incidence of re-infarction and the size of myocardial infarction and induces left ventricular remodeling after several months.

To date, two treatment strategies have been proven to be effective in the treatment of distal microvascular embolism, which are manual thrombus aspiration and intracoronary administration of abciximab.

Recently, the theory that deferred stenting can reduce microvascular obstruction has been suggested. The theoretical basis for the hypothesis is that prolonged antiplatelet therapy and anticoagulation for a deferral period may enable the resolution of the thrombus burden in infarct-related arteries, which is a substrate of distal embolization and subsequent microvascular obstruction. additional rationale is what is called the "vascular cooling down" to avoid mechanical stimulus in the milieu of active inflammation within an infarct-related artery in the early stages of myocardial infarction and prolong exposure to intensive statin therapy before stent implantation.

Based on this theory, four randomized control trials were published recently, but their results were different. According to the subgroup analysis of the INNOVATION study, in the cases of anterior wall myocardial infarction, deferred stenting strategy reduced not only the infarction size but also the incidence of microvascular obstruction. These findings suggest that the left anterior descending artery has more microvascular bed than the other vessels, and thus the positive result of deferred stenting could be maximized. However, these subgroup analysis results do not have sufficient statistical power to conclude deferred stenting is beneficial in the left anterior wall myocardial infarction, it is important to reaffirm the results with a large randomized control trial exclusively selected for left anterior wall myocardial infarction.

In this study, we sought to evaluate the impact of deferred versus immediate stenting in patients with acute ST-segment elevation anterior wall myocardial infarction on clinical efficacy and safety.

Study objectives The primary objective of this study was to evaluate 1) the clinical efficacy and safety of immediate versus deferred stent implantation in patients with acute ST-segment elevation anterior wall myocardial infarction; 2) the degree of microvascular occlusion reflecting distal microvascular embolization using Cardiac MR and 3) the LV strain using echocardiography.

Medical devices and therapeutic agents The medical devices and therapeutic agents to be used in this study are the treatment modalities that have been proven to be beneficial in the treatment and prognosis evaluation of acute ST segment elevation myocardial infarction in general. The stent is a third-generation drug-coated stent, and we intend to unify it as one type (Xience alpine, everolimus eluting coronary stent, Abbott, USA) in order to prevent the difference in results due to differences in stent types.

Expected effects of the research The treatment of acute myocardial infarction has been continuously developed not only in the revascularization of the coronary arteries but also in the improvement of microvascular perfusion. In addition to conventional thrombus aspiration, the use of Glycoprotein IIb / IIIa inhibitors such as Abxicimab has been used to improve the therapeutic results. However, it is also true that such treatment methods alone have limitations in the prevention and treatment of microvascular obstruction. Recently, deferred stenting has been attracting attention as a new method to reduce microvascular occlusion. Especially, deferred stenting is expected to have a positive result in left anterior wall MI with high microvascular volume. It is expected to be able to determine the effect of deferred stenting strategy on the incidence of clinical events and improvement of microvascular revascularization in patients with ST elevation anterior wall myocardial infarction through this study.

Clinical trial monitoring Monitor personnel designated by the investigator to obtain quality test data will review the clinical trial data at appropriate intervals to ensure accuracy, completeness, and compliance with the protocol. The monitoring personnel can investigate all documents and essential records held by clinical investigators or clinical trial laboratories, including the medical records (office, clinic, and hospital) of the subjects participating in the clinical trial. Clinical investigators and researchers should allow access to these records to the monitoring personnel. The monitoring plan will be conducted three times in total, at the time of registering the number of subjects corresponding to 50% or more of the total enrollment number, when the completed research subject reaches 70% or more, and immediately before the end of the study.