title: The late open artery hypothesis at the crossroad. The ACTOR study: aggressive versus conservative treatment of the infarct-related artery after acute MI. ACTOR Study Group.
abstract: The purpose of this multicenter study is to test the hypothesis that opening an occluded infarct-related artery late after acute myocardial infarction in asymptomatic patients without evidence of residual ischemia would reduce cardiac events over three years of follow-up. The search for an explanation of the complex relationship between the patency of the infarct-related artery and the clinical evolution of the patient who suffered an infarction led to the open-artery hypothesis, whose interpretation comprises two different components. The first component attributes the benefit to the fact that the timing and the method of reperfusion treatment induce a significant degree of myocardial salvage through early and persistent recanalization, and this is defined as the "time-dependent component" of the patent artery hypothesis. The second component ascribes the clinical benefit to late recanalization in conditions in which intermittent, early, spontaneous or pharmacologically-induced recanalization is unequivocally absent, and this is called the "time-independent" component. There are numerous mechanisms by which the patency of the infarct-related artery may potentially influence clinical evolution independently of myocardial salvage. Reperfusion may increase the stiffness of the infarct zone, thus limiting its expansion and dilation. It is also possible that restoration of flow through the vascular bed may provide a sort of "scaffolding", which limits the expansion of the necrotic myocardium. Patency of the infarct-related artery has also been suggested to confer electrical stability to the infarct area and could be the source of a collateral blood flow, thereby protecting the myocardium against future coronary events. Even if these data support the hypothesis that patency of the infarct-related artery has beneficial effects with regard to both LV function and survival, they do not provide definite grounds to change treatment strategy in post-acute myocardial infarction by referring all patients with occluded infarct arteries for mechanical revascularization. Hence, there is widespread consensus that a randomized study conducted in an adequately-sized population with clinically meaningful endpoints would provide the necessary degree of certainty. The ACTOR study should plan analysis of the status of infarct artery patency after the acute phase of myocardial infarction, excluding those patients who require myocardial revascularization on a clinical-angiographic basis and randomly allocating the remaining patients for PTCA or conservative treatment. If intervention with PTCA and stent for these patients is demonstrated to reduce clinical events at three years, then a policy of routine angiography after the acute phase of MI with the intent of percutaneous catheter revascularization for totally occluded infarct arteries would be justified.
mesh_terms: D015906:Angioplasty, Balloon, Coronary; D002986:Clinical Trials as Topic; D017023:Coronary Angiography; D003326:Coronary Circulation; D004452:Echocardiography; D004562:Electrocardiography; D005500:Follow-Up Studies; D006801:Humans; D009203:Myocardial Infarction / Q000188:drug therapy / Q000503:physiopathology / Q000628:therapy*; D011379:Prognosis; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012008:Recurrence; D012189:Retrospective Studies; D015607:Stents; D015912:Thrombolytic Therapy; D013997:Time Factors